How NOT to insulate your house

Sometimes insulation hides bigger problems.

The other day, I was talking with a friend of mine – an energy auditor who was a builder for decades. The topic came around to bad advice that “experts” give about insulating. It’s something that we both feel passionate about because homes get ruined and people get sick when innocent people follow this bad advice. We both adhere to a similar do no harm philosophy of  “if it’s worked for decades as-is, don’t mess it up!”

There’s a science to building and the tighter and more energy efficient you make a home, the more important it is that you do things “right.” It’s like the difference between making a log raft and a submarine. A log raft is leaky, but it’s forgiving because it floats by virtue of the logs. It doesn’t have to be water-tight. A submarine had better be water tight and structurally sound or you’re going to drown and get crushed by the intense pressures of the ocean.

Unfortunately, unlike boats and submarines, homes today are often built in the cheapest way possible, with little regard to physics. Renovations are even worse because people often hire unqualified “low-bid” contractors to do the work without realizing that the few thousand dollars that they save on construction may cost them tens of thousands to fix or even send them to the hospital due to mold or poor indoor air quality.

The problem is, people familiar with building science are extremely rare, as are the chances of finding a builder who knows how to make a healthy, energy efficient home. That’s why you’re here reading this now – you want to learn what not to do when insulating and how to do it right.

#1 – Insulate the attic after air sealing and reducing moisture

Adding insulation is one of those jobs that people think can be done blindly. Just throw some pink stuff up in the attic and you’re good to go, right? Wrong.

If you’re lucky, you’ll get away with this. If you’re not, you could end up with an unhealthy, moldy attic. Why?

Many homes are leaky and have insufficient insulation in the attic. This allows a lot of heat up to the attic. Warm spaces have less condensation risk than colder space so when you add insulation to the attic floor, you’re intentionally blocking some of that heat from keeping the attic warm. This makes the attic colder and a colder attic with moisture leaking from the house can result in condensation, mold and wood rot.

Bath fan ducted into attic

This is one of the main reasons that energy efficiency experts tell you to air-seal the attic where the insulation will be installed and ensure bath fans are properly vented before insulating. Air sealing reduces the amount of moisture that that can get into the attic, reducing the chance that you’ll end up with a mold problem. But, you want extra protection in the system because some moisture is inevitable. Maybe you got away without proper attic ventilation in the old house, but as you tighten things up and insulate, it becomes increasingly important to have good attic ventilation.

I personally don’t care whether you use gable vents or properly matched soffit and ridge vents, just do it right. If you use gable vents, it’s best to have two of them – one on each side of the attic to provide a good cross flow of air. If you use a ridge vent, you MUST have an equal or greater volume of air coming in to the soffits.

And that picture at the top of this post? That’s a wet mess of insulation caused by the builder neglecting to put an air and moisture barrier behind the bath tub. Instead, they were lazy and there’s a big hole with fiberglass draped over it – that’s worse than useless!

#1a – Turn off the humidifier

Humidifiers can destroy a home and make you sick. The more you tighten and insulate your home, the less you need to use humidifiers. And yet, I see very tight, new homes, being built with whole house humidifiers that dump gallons of water into the air. Moisture finds the tiniest cracks and holes and moves into spaces like the walls and ceilings. Much of it ends up in the attic where it can rot out your roof.

My advice to people as they add insulation is always “turn off the humidifier.” If the house is still too dry, find out where the air leaks are and plug those because that’s what causes dry air.”

I know this personally. Before I weatherized my own home, we’d have a humidifier going all winter. The air was so dry that my lips chapped and lightning would fly every time I touched the dog. But ever since we dealt with all the big air leaks, the humidifier hasn’t run once. It’s comfortable in the house all year round.

#2 – Choose your insulation carefully

Insulation is not a “one-size fits all” product. Insulation, like cellulose, that works great in the attic and the walls should not be used in many basements and crawlspaces where it can get wet. Likewise, fiberglass, which is ubiquitous, shouldn’t be used for the band joists in the basement or any other place where air sealing is required since fiberglass is does nothing to stop air movement.

You have to think about why you are using insulation in each location. For example, the band joist is often leaky, letting cold air in. It is also probably very cold because it may be exposed to the outside temperatures, making it a likely candidate for condensation. This tells us that you want an insulation that air seals and keeps interior moisture away. The perfect product for this is closed cell spray foam (as in the link above).

What about wall insulation? Walls are *usually* fairly air tight on the inside and leaky to the outside, with a few holes for electrical outlets and such. In general, walls are pretty forgiving about the type of insulation that’s used, but you can still screw them up. For example, a lot of building codes call for vapor barriers on walls, but using a vapor barrier on the inner wall AND using a tight outer wall can lead to horrendous moisture problems inside walls. This is an entire article itself, so I won’t go into more detail here. Just know that a conventionally built wall is usually forgiving, but if you start doing anything different, you need to be really careful.

Another insulation location is the attic. As noted in #1, you need to air seal before you insulate. But what if you could air seal and insulate in one shot? In fact, spray foam does exactly this. I love the stuff. Rather than having to spend days or weeks in a dirty attic, carefully caulking every crack and filling all the holes with cans of foam, and then carefully laying out insulation, you can instead just remove the old insulation and have a foam contractor come in and in a day or less, your attic will be completely air sealed and insulated. It’s really a superior way to insulate. I used it in all my own renovations and the results are awesome.

There are other places that are critical to consider. For example, cathedral ceilings. I’ve seen a lot of problems with insulated cathedral ceilings, especially those with tongue and groove planks instead of sheet rock. Because of potential moisture issues, I would personally never use a loose insulation like fiberglass in these ceilings. Moisture goes right through fiberglass and will condense on the cold underside of your roof. Even if you use vent chutes to provide an air space above the insulation, you can still have problems. So in choosing insulation for a cathedral ceiling, you really want a material that stops air and moisture from reaching that sensitive roof deck. Again, the ideal material is usually closed cell spray foam.

#3 – Insulate continuously: like a jacket for your home

One of the biggest mistakes people make is ignoring the big insulation picture and how it all connects together. You can do everything I’ve written about above perfectly and not have the insulation work at all. How?

Imagine an ice chest. This is just a box of insulation, sealed on all sides. Ideally, this is how a house is made. But what would happen if you took the top of the ice chest and moved it a couple of inches away from the cooler? It’s not air tight any more and whatever is in the chest would end up at room temperature. Same thing with a refrigerator – what happens if you leave the door open? The fridge has to run continuously to try to get cold while all the heat from the room rushes in. Any child would look at these examples and say “duh!” If this is so obvious, why do highly paid builders often construct houses that are no different than an ice cooler without a lid? Or to use the jacket analogy, would you wear a jacket with the zipper wide open?

Unfortunately, the more complex the home’s design, the harder it is to ensure continuous insulation. Modern homes, with a dozen different roof lines and a hundred walls can be difficult to deal with properly. I’ve seen contractors start by insulating under the roof in one place then switch to insulating the walls in another, rendering the roof insulation meaningless.

One trick to use is the “pencil trick.” Take the architectural drawing of the house and, without lifting the pencil, draw a single line representing the insulation around the house. Wherever you lift the pencil would be a discontinuity where outside air could short-circuit the insulation, rendering it useless.

#4 – Be smart – Don’t break the original home’s design

Going back to the “do no harm” principle, you have to be really careful not to “break” the working design of the house. I’ve seen insulation contractors do really stupid things that lead to moldy, rotten homes. If a house was built 50 or 100 years ago, and it’s never had a mold problem, there’s probably a good reason why. For example, there are a lot of older homes build with plaster and lath. These have an air gap between the exterior stone wall and the plaster interior wall. That air gap allows water to drain and dry out. But yet we see people putting cellulose and other non-water resistant insulation into that gap. That’s like sticking a sponge in there. It will soak up the water and likely end up in a moldy, rotten mess and useless insulation.

There are other stupid things you can do. For example, pretty much every roof that goes on gets a ridge vent. But why add a ridge vent to a 50 year old home that already has gable vents? Worse, that 50 year old house won’t have matching soffit vents. The result is a house that is less energy efficient and more prone to mold and rotten roofs because the ridge vent sucks the humid air out of the house and into the attic.

If something doesn’t make sense to you, don’t let the contractor do it. Sometimes they’ll be offended and say something like “I’ve been doing this 30 years, I know what I’m doing.” Well, maybe they’ve been doing it wrong for 30 years! If you have any doubts, get another opinion or two. Or post a question on my Q&A section. There’s a science to this and there’s a good chance that your contractor doesn’t know the science. I’m not saying that they’re not a good contractor, but they may simply not be knowledgeable about the current best practices. Regardless, if they’re not willing to listen or back up what they say with facts, you should find another contractor.

#5 – The home is a complex system

I touched on this in #4 with the discussion of the ridge vents. A building is a lot like a human body – what you do in one place affects things in another. Just like adding a ridge vent can lead to increased energy bills and a rotten roof, you can do other things that have unintended consequences.

For example, many utility rooms with furnaces or boilers have large vents that provide fresh air into the room. Often, people look at these as sources of cold drafts (which they are) and close them up. The problem is, they were put there for a reason – they supply fresh air for the combustion that the heater is doing. Closing the vents and sealing the utility room can lead to improper heater operation or even carbon monoxide problems which can lead to illness or death. Unintended consequences can be deadly.

Another example of unwanted side-effects of insulation – spray foaming a house without ensuring adequate air supply.

I’ve been known to say “a house can never be too tight.” Unfortunately, you can screw things up by making a house very tight without considering fresh air and humidity requirements. Using spray foam, you can make a house that has extremely low air leakage, so you have to consider introducing fresh air using an HRV (heat recovery ventilator). There are standards for this (See ASHRAE 62.2 and related). Basically, you want a certain amount of fresh air per occupant in the house. For typical families, this amounts to about the amount of air introduced by a bath fan. Not much! But often, people adding spray foam insulation either don’t consider or don’t know about the fresh air requirements, and the results can be horrible.

Concrete example: you make a house super tight at the same time as you remodel the kitchen and add a powerful new range hood. When you run the range hood, it creates a suction so powerful that it can sucks the exhaust fumes from the furnace and water heater back into the house. Again, this can kill you. No joke.

Less extreme example: you tighten up your house and then you find that every time you make a fire in the fireplace, you end up with a huge amount of smoke in the house because there’s just not enough air going up the chimney. To compensate for this, you have to open a window whenever you have a fire.

There are numerous situations like this that can occur if you “just insulate” without considering the complex system that is your home. Please, go into these renovations with open eyes. If you have any concerns, call in a trained energy auditor/building scientist. I’m also happy to answer questions posted here. But be aware that in order to do this right requires a series of precise measurements that take into account a variety of factors about your house and various appliances in the house. In some areas, these measurements are required if you are adding a certain amount of insulation or doing significant renovations.


159 thoughts on “How NOT to insulate your house

  1. Hi, I have CBS block walls, and I wanted to stuff the visible, empty spaces in the block with leftover bat insulation. The reason being, I have sealed the block with white UGL and like the exposed look. Is this ok to insulate this way?

  2. ‘I’ve been doing this for 30 years’, that made me laugh; I’ve been hearing that a lot lately! Currently trying to stop the intense draughts in a 1930’s house I’ve just moved into (and failing). I’ve spent £5000 on insulation, and it hasn’t worked. Every gap has been sealed by the way. The draughts could be better described as air infiltration as they are not from an obvious cause and seem to be everywhere. I now know insulation is NOT an airtight barrier. The contractors do not seem to know that.

    • It would be funny if they didn’t always do such a poor job with your money!
      Perhaps a thermographer could come in and use their thermal camera to track down the cold spots. I’ve found that the thermal camera often reveals big problems that ordinary visual inspection misses.
      Good luck with your project. Hope someone can help you get to the bottom of this.

  3. Hi. Interesting article and comments. It’s been interesting learning about insulation!

    My situation: I’m in NJ, in half of a duplex/twin home that is 21 years old. The 2nd story has always been too hot or cold compared to the 1st floor. I replaced windows years ago, and it helped, but there’s still a difference. I also had an issue with bats in my attic–got an animal pro to remove them correctly. Then I just had a new roof put on, and any openings sealed.

    Soooooo…. I wanted to get rid of the parts of the insulation with bat droppings, and improve the insulation in general to help the 2nd story. Got an estimate to just blow in some insulation. The second estimate I got involved more — they said that just blowing in insulation would cause moisture/mold issues in the attic, so they recommended to air seal the attic, fix the baffles, and blow in more insulation. But, this would change the house air flow, and they said that I would need to get a hot-water heater (1st floor) that vents directly outside – otherwise if I kept my current hot water heater, there is a CO risk. Wow — everything is connected! And your article really emphasizes how you can fix one thing and make something else unsafe.
    Anyway, NJ has grants and 0% loans to cover the cost (NJ Home Performanceprogram). My gas/electric bills aren’t high, so I don’t think I’ll recoup the $$ anytime soon, and I also wonder if it’s a $$ numbers game to inflate prices. But the 2nd floor would be more comfortable, I hope.

    I’m just torn — I wanted to fix the insulation, and now I’d be getting that and a hot water heater ( mine is 2 yrs old!) — and I read bad reviews on those tankless ones…

    I’m just trying to decide if doing this bigger program is the “right” way to go, vs. just putting in more insulation like the first contractor said.

    Thanks for posting this article and the comments. It’s helpful for those of us who have never dealt with these topics before to hear from an expert.

    • Your second contractor is kind of right. Large scale changes in the home that involve heavy air sealing and insulation can affect the ventilation of the home and cause conventional gas water heaters to backdraft – a dangerous situation. However, they’re required to pressure test the home under worst case scenario in order to verify that this is the case. It is definitely not a sure thing.

      Before you launch into the project, I’d recommend having an independent energy auditor come in and give you an evaluation so that you can focus your efforts. They will also run the tests to see the current state of your home which will be valuable if you get additional work done. It could turn out that you don’t need additional insulation and it’s more of an air conditioning issue upstairs. Often, the floor furthest away from the air conditioner blower gets the least amount of cold air, leading to uncomfortable conditions. More insulation can help the situation, but it could just be that the system needs to be rebalanced to provide more air upstairs.

      Sometimes, people ask me why they should get an energy audit performed if they know they’re going to do the work anyway. The answer is that a qualified energy auditor* will be able to tell you exactly what you need to do and what you shouldn’t do. They’ll guide you through the process of updating your home so that you can properly evaluate quotes you get from contractors. They can also help answer questions like the one I raised above – is it an insulation problem or an air conditioner problem? Or both? It can be really frustrating to spend a lot of money “fixing” a problem only to have it make no difference.

      *A qualified energy auditor is going to be someone independent and who has been doing the business for a number of years. There are a load of people who took short seminars to get their BPI certification but who really aren’t qualified to do the job. In NJ, pretty much every contractor was required to take some of these seminars so that they’d have the basic background and wouldn’t kill anybody. But that doesn’t make them a skilled auditor. You want someone who is skilled at troubleshooting and understands the science of buildings – how it all works together. You should be able to find someone in NJ. What part of NJ are you in?

      • Hi Ted
        Thanks for the reply!
        I’m in South Jersey — not far from Philadelphia.

        Another question that occurred to me as I’ve been reading and thinking about this: The 2nd contractor would seal the attic, but not the part where my living room cathedral ceilng is. In the attic, that portion is sloped, and also can’t be accessed easily — there are pieces of plywood blocking the way (I guess so nobody falls down the slope!).
        So, only the flat part of the attic would be sealed, but not the cathedral ceiling part.
        So, would I get the condensation/moisture problem because that’s not air sealed?
        And if they pressure test the attic, well, it wouldn’t be completely sealed.
        Hmmmm…. the plot thickens.

        I like your idea about an energy auditor and I’m going to look around. Thank you for your response!

      • I’m going to defer comment on your subsequent question about the Cathedral ceiling. This should be looked at. I would not want to lead you astray. It sounds like you’ve done your homework. The main thing is to keep that area free of moisture sources, like recessed lights and other holes that could allow interior moisture from intruding.
        You should be able to get someone good in this area. There’s a pretty active community of green builders and consultants around here.

  4. This is a great read. Good job. My information. South Florida CBS (concrete block and stucco),ranch home built in 1980. The original gable roof was concrete tile that was replaced with a quality composition material two years ago. Before we purchased it. Very minimal ceiling insulation. I have zero problems with moister, leaks, humidity, dryness. Question. I am putting in low e impact and wind mitigated windows and doors. A costly job. This will tighten the house considerably. Insulating the ceiling was next logical thing on the list. I figured, tighten it up more and enjoy the lower power bills. I thought! After reading all in you website, I’m confused. Very humid climate. Attic is super hot. Roof has ridge vents and sofit vents. Would you leave it alone? Don’t want to create problems where none exist. Other than the big a/c power bill. Or, would you do more to reduce the power bill? I am a little bit of a green geek but only to the law of diminishing return. Thanks in advance.

    • Thanks Steven!
      I’m surprised the house was built with minimal ceiling insulation in South Florida – you must bake in there!
      I would certainly add insulation. As long as the contractor takes care not to mess up the ventilation in the attic by installing proper baffles so soffit vents aren’t blocked, you should be good. You can end up with condensation on cooler surfaces such as ductwork, but that would happen with or without insulation.

      Ideally, I’d go high density closed cell spray foam and encapsulate the attic since that blocks moisture. It also locks the house together making it less prone to damage during hurricanes. Here’s a short article on this.

      You might also contact your local building official/code enforcement officer to see if they have any recommendations for your specific construction. Often these folks will be a wealth of knowledge about the specifics of local building since they’ve probably seen it all, and in other houses just like yours.

  5. Hi, Great article. What are your thoughts on converting a vented crawlspace to an unvented crawlspace? I live in central NJ and have a 1960’s split level home which has a vented crawlspace attached to a basement. I am contemplating whether or not i should seal the vents and insulate the walls with foam board (or spray foam) as well as seal the rim and band joists. In addition to this, run a dehumidifier to address moisture and humidity. The floor is concrete. I’ve been reading numerous articles online saying that unvented and properly insulated crawlspaces are a better option. One of my concerns is that my hot water heater and furnace are in my basement and if I seal and insulate too well I might negatively impact combustion and or cause CO build up.


    • All your comments are on-target – most in my field now endorse the idea of an insulated, unvented crawlspace as long as precautions are taken to avoid “unintended consequences”.

      Ideally you would want to have your house pressure tested with the connection between the basement and crawlspace sealed off to simulate the conditions you might get after sealing the space. Then you could determine if there was risk of adverse effects on your water heater and furnace. You’d run a “worst case” depressurization test that involves turning on every vent fan in the house, running the dryer, and anything else that might lead to a negative pressure in the basement that could lead to problems. The pressure would be measured with a very sensitive monometer.

      Barring the full test, a couple things to consider are:
      – Are the water heater and furnace naturally vented as opposed to direct or power vented? Modern, high efficiency furnaces draw combustion air directly from the outside and expel exhaust through another direct, powered vent.
      – Are there other things in the basement, like a dryer, which would expel air outside?
      – If your water heater is an older style, might it be time to replace it with a direct venting unit? Same question for the furnace?

      Chances are good that in that vintage home, you won’t have issues because they were pretty leaky. But, better safe than sorry!

      There are a lot of contractors in the area who would be qualified to run the depressurization tests for a couple hundred dollars, so it may be worthwhile to have someone come in and walk through your plans and do the testing.

      • Hi, Thanks for the response.

        Unfortunately, my furnace is not a high efficiency furnace (the sticker on the unit says 80 % efficiency) even though it is only about 6 years old. My hot water heater is very old and I need a new one badly. I should look into getting a direct venting water heat?

        I will look into contractors to perform the depressurization test that you recommended in your response.

        Also, I’ve recently noticed that I have little to no insulation in my attics (split level). I’ve contacted 3 spray foam contractors recently and am waiting for a response. From your article, it appears you prefer spray foam over fiberglass/cellulose. Are there any specific questions I should ask the installers when they come to give a quote?

        Do you have any concerns about the safety of spray foam?

        Thank you.

    • Definitely replace the water heater with a direct vent model when you replace it. If you plan on doing it in the next couple of years, you may as well replace it now so you can reap the benefits of the higher efficiency and safety. In addition, if it’s very old, chances are good that it will develop a leak and the last thing you want is hot water leaking into your house. I’ve seen homes ruined by water heater leaks!

      As for the furnace, if it’s only 6 years old, it should last a lot longer. Depending on your energy bills and long term plans (are you planning on living in this house for many years?) it may or may not make sense to replace it. Usually, I wouldn’t advocate replacement of a newer unit based on the finances. But, in some situations it might make sense. For example, like you noted, if you’re planning on really sealing up the basement, and you think you’ll be in the house for many years, and your heating bills are high, then you may wish to consider it. For example, suppose you get a system that averages 10% more efficient and you pay $2,000/year for heating. That’s only $200/year saving. With a replacement high efficiency furnace costing, for example, $5,000, it would take 25 years to pay it off. That’s a long time!

      There are things you can do to bring in combustion air in a sealed basement so as to avoid backdrafting problems. For example, it’s common to install a section of duct from the outside to right next to the furnace. The duct terminates into a large bucket. When the furnace runs, it pulls in air from that duct. Why the bucket? Because the cold outside air will pool into the bucket and reduce the amount of cold air that flows freely into the house. It’s remarkably simple but can work quite well.

      Regarding foam – most building scientists greatly prefer closed cell spray foam because it’s a better insulator, a much better vapor retarder and actually strengthens your home by essentially gluing it together.. Contractors often prefer open cell because it’s cheaper and easier to install. Safety wise – many jurisdictions insist on coating the foam with a flame retarder to reduce fire issues. Be sure to check with local code enforcement officials to learn what’s required in your area.

      As for questions – ask how long they’ve been in the business of spraying foam and definitely get references. Foam can be a tricky business but a lot of contractors saw easy money in the last decade so many unqualified contractors bought the equipment. I’d want someone who has been doing it for more than a decade. Also, check Angie’s List for contractor recommendations. They’re usually quite accurate.

      • Thanks again for the quick response.

        I have a company coming on Friday to perform a home energy audit. They are qualified and certified, meeting the NJ Home Performance program standards. I’m going to see if I can qualify for the rebates being offered.

        On the phone I’d mentioned to them that i would like closed cell foam insulation installed in my attic. They said that spray foam is a fantastic product and works extremely well but, according to their company, the added benefits do not outweigh the extra cost as compared to properly installed cellulose and air sealing (they said its ~4-5 times more expensive). They are more than willing to do it, but they consider foam to be more task specific. Is this statement true or would you recommend I push for spray foam?

        Thanks again.

      • If done properly, air sealing and cellulose can work well. It really depends on the installation.
        However, if you want to insulate under the roof instead of on the attic floor, it’s much better to use the foam. Also, you have to ensure proper attic ventilation above the cellulose or you run the risk of rotting out the roof. Definitely ask them if they feel that there’s adequate ventilation to avoid moisture problems in the attic. Even with careful air sealing, you need excellent ventilation. Example – a friend of mine who was also an expert spray foam installer used foam on the attic floor and thought with that it was OK to not ventilate the attic. He ended up calling me for help when he got icecicles in the attic! So just beware.
        On the other hand, when I added insulation to my house, the installer blew a foot of cellulose on my attic floor and I have had no problems since I have a continuous soffit and ridge vent system. So it can work well.

  6. I live in Guilford County in N. C. in a house built in 1939. In 1962, the original owner converted the attic space to living space, thus creating two knee walls that run the 32’ length of the house front and back. The house has a gas split HVAC system, from one unit. My problem is that the rooms are ok but not great in the winter, but uncomfortable in the summer and the ac can’t keep up.

    The attic space currently has one gable vent on the front of the house, and one electric non functioning power attic vent on the back roof of the house. There are no soffit vents, but there is a soffit area of 4” wide running the length of the house where I plan to add soffit vents. I am contemplating the continuous metals ones that come in 8’ lengths that are 2 ½” wide, and then installing gable vents on either end of the tiny triangle attic space above the ceiling area of the rooms. The roof shingles are in good shape and don’t need to be replaced for another 7+ years, otherwise I would go ahead and install a ridge vent.

    Above the sloped ceiling area of these rooms, there is currently no insulation. The rafter space is 5 1/4”deep, so I have added an R-13 fiberglass batt in this area, with the vapor barrier to the living space. On top of that I have laid a sheet of perforated radiant foil barrier material leaving me an air gap of 1 ¾” between the roof decking and the barrier. I must say that this has been the MOST challenging part of the task so far, as it is difficult to maneuver in such a tight space. The purchase of a hard hat was necessary to prevent hitting my head on nails from the roof decks when inserting the fiberglass insulation. Now… this has provided me with a less than perfect solution…but…it is better than no insulation at all and short of ripping out the sheetrock, no one I talked to could come up with a better solution.

    In the “accessible” attic area behind the knee wall, I have fastened the same radiant foil barrier to the bottom of the rafters, following the guidelines on the proper distance from the eaves area. Just this alone has reduced some of the heat gain and is well worth the $110 investment. By the way, I am doing this in steps, and trying to address the “sun” issue first prior to air sealing and beefing up the insulation (we are working in the evening when it is cool enough to gain access without a heat stroke.)

    As to the tiny triangle of attic space above the ceiling of these rooms, I am assuming that there is little to no insulation up there. I have yet to check… I’ll be cutting a few scuttle holes in these rooms to gain access to address what can be done. (Afterward all but one of the holes will be closed up) I want to get at least an R-38 up there, and then lay the perforated foil barrier over it, so it can reflect the heat build up back out through the roof. I realize this is the least effective way to use the barrier, but from what I read it should help. (The dept. of energy has some helpful info on radiant foil barrier materials.)

    After the above task,… the rest should be a piece of cake. I plan to put rigid foam board under the knee wall area to stop air from the lower level getting into the attic space and at the soffit bay area to keep insulation from blocking the soffit vent area, air seal these and other areas before I install R-19 on the knee wall area, and R-38 or greater between the ceiling joist.

    A friend has told me I am going to a lot of time and trouble and will be disappointed in the results. Now none of this is a perfect solution, but from my extensive reading, reading, and more reading (some very contradictory by the way) on how best to address these problems on a limited DIY budget; I think this should go a long way in creating a more comfortable environment for the folks that live in this part of the house. Hopefully my HVAC system will not have to work so hard.

    Thanks for any input or please tell me if you think my efforts are going to be fruitless (you won’t hurt my feelings…I am teachable.)  . I am doing this in stages, and have only invested in the radiant foil barrier, and the r-13 for the sloped area (I haven’t done the back side of the house with the r-13 yet as it is more shaded. so if you have a better idea for this area I am open to suggestion). The rest is being purchased as the work progresses.
    Many thanks~!

    • Wow, I give you a lot of credit for what you’ve done. Those sloped areas are really tough to deal with, especially being careful about leaving air gaps and then putting in the radiant foil! If only I could get any contractors in this area to be so diligent 🙂

      Going from no insulation to the R-13 plus radiant should make a tremendous difference. You should reduce at least 80% of the heat gain (didn’t do the calculations, but conservatively estimating going from an effective R-2 to R-10).

      I’ll be very interested to hear about your actual results as the summer heat hits. You should be able to feel a tangible difference between the insulated and uninsulated areas. You’ll also probably be able to feel where the rafters run through the ceiling due to the thermal bridging there.

      Please let me know how it works out.

      • Hi again TD,

        The heat hit the past few days…and it hit hard w/close to 90 degree days, so I will not be able to complete all of the sloped bay areas until early fall, I did however go ahead and lay the foil barrier in these areas to be reflective until I can get back to complete the insulation work. Amazingly the areas behind the knee walls where I have the perforated foil barrier stapled to the bottom of the rafters is making a HUGE difference in reducing the heat gain. I’ve not stuck a thermometer in there, but, I can easily tell it is doing the job it is designed to do as there is NOT the blast of heat when the hatch door is opened when gaining access to the area as there has been for the past 2 summers.

        As suspected, after opening up a scuttle hole and checking out the tiny attic area above the flat ceiling of the rooms…there is NO insulation. Actually this is a good thing, because all of the other insulation (what little there was) that had been installed in the knee wall and joist areas, was installed backwards, with the vapor barrier toward the attic space, at least I don’t have to remove anything from up there. Fortunately there are only 3 areas that require air sealing, two ceiling fan combos and a light fixture. I’ve nick named this space the devil’s triangle, as it is hotter than you can imagine, and even at 3:00 a.m. after the rest of the house has cooled off, this area is still suffocating (all the more reason to get the ventilation work done next.) The ceiling joist in this area are 2 x 4’s with most bays being 16″ oc, some narrower. Now that I know what I am dealing with, my plan is to air seal, lay R-13 in the bays, and then run either unfaced R-30 or R-38 perpendicular, topped w/the foil barrier, while making sure I allow for good air flow from the sloped bay areas. The idea of cutting multiple scuttle holes is the only way to go, which will allow me to work in 3 or 4 bays left and right of each hole.

        After opening all 4 areas, I may even find that I can attach the radiant barrier to the bottom of the rafters, before insulating ( I would prefer this over using it as a blanket…we’ll see) As I said, when the insulation is done, I’ll button all of these openings except one access hole. I’ll finish up this area, tape, dope, and sand the sheetrock, and hopefully be good to go.

        I think only a crazy homeowner would go to such pains. Most contractors, understandably, would want to just rip out the sheetrock and start from scratch, but since I have the time to work on this in phases, I think this plan is going to work pretty well. If you are interested, I’ll definitely keep you updated as the project reaches completion. Home insulation is an art unto itself, and I’ve gained an appreciation for the folks that do the job correctly~! I’ve been in the building industry for 34 yrs. as a kitchen designer and have been on hundreds of new construction and remodeling projects, and have great respect for the professionals in the building industry. Have a great week~!!!


      • Great report! So glad that the foil is having a great effect. Others will certainly be interested in actual results like yours.

  7. Pingback: How To Better Insulate Your House | Tiriya5

  8. This is a great article. Before the winter we had our attic insulated professionally. It reduced our energy bill roughly by 50% for 4 months in a row. Unfortunately, the humidity levels in our house are very high now. We are now seeing ghosting on the top of or walls and spots in our ceiling. The fixed a bathroom exhaust to vent out of the roof, but that didn’t fix it. They also put baffles in and that’s when we learned that there were no soffit holes. We have gable vents, ridge vents, and no soffit vents – this is how we bought the house and it was working well without the sealing/insulation. I am at a loss of what to do. Should we have them open up some sealing or remove some insulation? Should we open up soffit vents? Should we add an attic fan?

    • Thanks. Glad you’ve seen substantial energy reduction. Unfortunate about the humidity but that’s fairly common if the contractors don’t take a “whole house” approach to the job. I have to admit, it’s hard for the individual contractors – insulation, Heating/cooling, builders, etc. because there’s a lot to understand with tighter, more efficient homes. Practices that used to be commonplace are now leading to issues like you’re seeing.

      On to your situation.

      I’m a little confused – could you clarify for me? I don’t want to give you advice based on faulty assumptions on my part.

      When you say that the humidity in your house is now very high, and describe the problems you’re seeing, I’m reading that to mean inside the living space of your home. Is this correct?
      You then go on to talk about issues in the attic which should be mostly unrelated to humidity in your living space. Am I reading this correctly?

      I’m going to attempt to answer assuming the it is the humidity in your living space that has become a problem.

      Firstly, I wouldn’t change anything in the attic at this point. The issues with soffit vents etc. shouldn’t affect the humidity in your living space.

      Next, since your home is now “tighter” than it was, there’s less energy-stealing drafts, which is probably why you’re seeing so much reduction in your energy bill. The side effect is that there’s less outside air coming in to flush out the humidity in your home. That’s fine, you want a tight house. But you need to look at where humidity is coming from that is causing the elevated humidity in your home.

      There are several common sources of elevated home humidity (during colder weather):
      – Wet basement/crawlspace – Do you have any dirt floors or water problems in the basement or crawlspaces under your house? Are the gutters draining properly, away from the foundation?
      – Humidifiers – leaky homes can be uncomfortably dry, so people install humidifiers. When the homes are tightened, they often forget to turn off the humidifiers. If you have any, make sure to turn them off so they aren’t adding moisture to your air.
      – internal moisture sources – lots of plants, showers, cooking – all can contribute substantial moisture to the air. Does everybody in the house use the bath fans when showering? Do they leave them running for a half hour after showering? It’s very important to flush all moisture out.
      – Anything else you can think of that could add water to the air?

      These tips should help to narrow down the factors that might be leading to your elevated moisture. Now that it’s getting warmer, and you’ll likely be opening windows and flushing out the air, chances are that will alleviate your problems. But you’ll want to resolve them before next winter.

      Drop me a reply once you’ve had a chance to look into some of these factors.

      • Thanks for your quick response! I’m sorry for the confusion. We first saw moisture in the attic – in the form of frost. That’s when the HVAC company saw the exhaust leaking into the attic and vented it out via the roof. Now that it’s not cold anymore its hard for me to tell how moist the attic is.

        Then, after we began seeing the ghosting on the ceiling and walls, we realized the new humidity problem in the living space. We’ve checked the obvious causes for moisture and have not come up with anything. The drier is properly vented. We open the kitchen window when we cook. All the bathrooms have exhaust fans. There is a humidifier on the furnace, but it’s turned off. The basement is mostly finished and dry. We just have a couple of small plants in the kitchen.

        If the attic isn’t properly ventilated can it somehow backup or push down into the living space? Or, now that the house is “tight”, what do we need to do to allow the humidity to leave the house?

        Thanks for your help!

      • I have the same issues in my home after air sealing. I have experienced no utility savings as I am constantly running exhaust fans and dehumidifiers to reduce the humidity levels in my home. Opening an window and running a continuous 30 cfm bath fan has helped in the winter but what do you do in the summer to reduce humidity and ventilate the house when it is hot and humid outside?

      • Interestingly, summer is often better because the air conditioning is remarkably effective at removing humidity. The spring and fall are often hardest due to rain and moisture combined with no air conditioning.
        One big thing to check is proper gutter drainage. If the downspouts dump water closer than maybe 6′, then the water can saturate the ground around the foundation which leads to all sorts of moisture problems in the house.
        I recommend that everyone walk around the house when it rains and make sure that the gutters are properly functional. If they are overflowing on the ground next to the house, you will likely have moisture problems in the house.

    • Ok, that makes sense. Attics will often see frost after being insulated since they’re now colder since all the heat from the house isn’t being lost. That’s one of the “unintended consequences” – fix one thing, break another. However, at least it’s moving in the right direction – it proves the insulation is working. I’m glad the HVAC company found the bath venting problem – that is a huge problem that has led to many a rotten roof. IMHO, any contractor that vents bath fans into the attic should be forced to pay for all the damage they cause!

      Now, the question is how to deal with the newly visible issues in the living space.

      I’d recommend that you get an inexpensive humidity monitor so you can put numbers on the moisture levels you’re seeing. I bought a bunch of these to give away to my clients years ago and if you send me your info, I’ll drop one in the mail to you. I’m emailing you with my contact info.

      The shadowing could be any number of things. I’ve seen a super-insulated home develop these issues, which, surprisingly, don’t necessarily indicate any problem. In that case, you could see shadows of every joist in the ceiling of an upstairs bedroom because those areas were very slightly cooler. The occupant burned candles and gas lamps which generated a very fine soot. This accumulated on the slightly cooler areas, leading to the shadowing. Is it possible that you’re seeing something like this?

      I’d also double check the humidifier and ensure that the water supply to it is turned off. Check the pad of the humidifier (if it has one) to ensure that’s dry.

      Do you have other indications that the humidity is elevated in the house?

      • Drainage is fine and the basement is actually less humid than the living space in the spring and fall my question is how do you economically ventilate and expel moisture from the home after air sealing and insulating the attic? or should we remove the airsealing and insulation from the attic to return the house to its original form? We are not benefiting from any cost savings the way it is. these so called energy efficiency updates have cost us more money in utilities and is damaging the interior of our home with high humidity. Maybe these retrofits on older homes should not be done?

      • Usually, Insulation itself isn’t going to make the house more humid so there’s no point in removing it. The air sealing reduces the amount of uncontrolled air coming in from the outside. But it also means that you need controlled ventilation. Most building codes now require ventilation tests after substantial air sealing and insulation to detect conditions that cause these problems.
        A tight house should be easier to control moisture throughout the year because less outdoor moisture enters. But, you have to control the sources of moisture in the house better.
        The best thing is to get a home energy evaluation to check out the conditions in and around the house. There are specific quantitative tests that are revealing. Look for a certified BPI home tester.
        In any case, you shouldn’t pay more to dehumidify and ventilate than the savings from air sealing and insulating.
        Did your contractor take measurements before recommending running the fans constantly? If not, that could be doing more harm than good. For example, you probably don’t want to run it 24/7. Running it when it’s humid out can bring in a tremendous amount of water vapor. I wouldn’t run it overnight or early in the morning or when it’s humid outside unless proper testing has been done.

      • He specifically picked a BPI certified contractor to do the upgrades in our home so it would be done right. But alas it has not. The came back and did a blower door test and installed the continuous run exhaust fan as a fix. But it apparently is not a fix and they have no other recommendations. We are at a loss for what to do during humid weather

      • ok, that’s a good start. Their tests are usually good. Did they leave you with a report? There should be a number of natural air changes per hour. It is abbreviated NACH or ACH natural.

      • This is what we were told.
        Your Blower door result was 1,485 CFM 50.

        You are in what we would consider the gray area of when mechanical ventilation should be added. The BAS for your home is 1,785 and 70% of BAS is 1,250. General practice is to recommend ventilation when you are in between 70% and 100%, but it is only required to add ventilation below 70%. We have many homes out there in between 70% and 100% (including my own) whithout adding any mechanical ventilation, with no issues. IN light of the humidity issues in your home, we would recommend it more strongly for you than most people. The BAS Calculation and CFM 50 results is based on your primary space, not the breezeway, as that is semi-disconnected

      • Thanks for giving me the complete answer, that’s very useful information. Because you are in that gray area it is not essential to run the fan full-time. I would especially recommend turning it off when it is humid out especially raining but usually also in the mornings when the humidity can be high.
        In general, people are very conservative with ventilation because they want to ensure good indoor air quality. But in your specific case where you are plagued with humidity comma you have to use that extra ventilation very carefully. Hope that helps

      • Thank you for your recommendations. Would using an erv be better in the humid times of year when not running the hvac system. Spring and fall

      • That is an excellent point. Precisely for that reason, I installed an ERV in my own home. My house has very similar numbers to yours, and I’m pretty conservative about running the ventilator. During the winter I run it quite a bit because the house is shut up all the time and you need the fresh air. During spring and fall I sometimes use it and during the summer I’ll use it if the air starts to feel stale. I personally don’t care for the steady ventilation fan usage without some sort of energy recovery.

    • From what I have read, you are not suppose to have gable vents if a modern “ridge vent” has been installed. Also, for a ridge vent to work properly, you must have some sort of soffit or roof vents to allow for air intake to exhaust out to through the ridge vent. When we had a new roof installed last summer, the company installed a ridge vent, didn’t install any air intake vents at the bottom of the roof and overlooked the fact that we did not have soffit vents. Upon reading the warranty from the shingle manufacturer, all warranties were null and void if the ridge vent was installed without soffits to balance out the air intake and exhaust. The roofing company had to in turn take out the bottoms singles and install a “drip edge vent”.( All of this was really frustrating because you hire someone to do a job correctly and not have to feel like every single step of the process has to be scrutinized, researched, and double checked to make sure it is done properly. Makes me want to live in an apartment.

  9. So I hired a contractor to come and install blown in insulation in my attic due to extremely high energy costs this past winter (first year in the house). However, now that I am climbing around in there i realize a potential problem before they come out to blow in the cellulose. The original plaster ceilings are about 12 feet high however sometime since the house was built int the late 1800s there are lower sheetrock ceilings (10 foot ceiling) that have been installed- if they blow insulation over the old plaster ceiling will this do anything to actually keep the heat in my home next winter?

    • That’s a very good question! It all depends what’s causing the high energy costs. If that cavity between the plaster and sheetrock ceiling has air leaks into it (that is – if it’s a “cold” space), then insulating above the cold won’t help. On the other hand, if it’s a pretty tight cavity, then you’d likely be fine.

      The $10,000 question is really what are the contributors to the high energy costs. Old homes are notoriously drafty and many have no insulation in the walls. You could have perfect insulation in the ceiling and it would make little difference if the walls have no insulation and the house is drafty.

      This is why I typically strongly recommend people have an independent energy auditor come in and find the major contributors to high energy costs. With that information in hand, you can prioritize the upgrades, putting your money where it will do the most good. In addition, qualified auditors will understand how the different parts of the house work together and help you avoid unintended consequences, which can be quite serious. For example, insulating a home could, under certain circumstances, lead to conditions which are favorable for mold growth. Or worse, well intentioned, but improperly carried out air sealing could cause carbon monoxide issues with combustion devices in the home (furnaces, etc.)

  10. HI, i’m remodeling an old 1920’s house in seattle(city of lake stevens) area. the building inspector mentioned if i exposed any outside walls i would be required to fill that space with insulation. well i’ve exposed a few. however, my understanding is tossing in insulation in an old house meant to breathe can cause more damage than good. it had drywall put over a some sort of 2″ lap board then 4″ stud, then exterior has 6 or 8″ boards on the stud with aluminum siding over that. we want to replace the exterior siding. would we use a tyvek there? along with fiberglass insulation then add vapor barrier before applying the drywall. would that even do any good with a wall right next to it that remains as is? seems like adding vapor barrier to only parts of the house is worthless. i dont want to create a moisture problem.

    • Bill, those are great questions you raised. You live in a tricky climate. High outdoor humidity means most of the moisture drives from out to in. But you still have moisture in the house that can migrate out. So vapor barriers can be tough. Logic tells me that if you are going to use any, it should be on the outside to keep the heavy moisture out of the walls. But, as you noted, if you are only doing a few areas, it may make less difference to the overall solution.
      I haven’t worked on your type of job and would defer to local experts. I believe that there are many green builders out there who should be able to lend their expertise. I suggest talking to various building professionals and get a recommendation for a good building science person.
      Sorry I can’t be more helpful.

  11. HI, I live in a 50’s 60’s ranch home in central NJ. All the walls are made of cinderblock construction. The interior walls on most of the home is wood and plaster lathe or sheetrock ( its been renovated a few times). My concern is with one room that is 22’x18′. It used to be a 2 car garage and was converted to a family room. I have been in the home for 20 years and we don’t use the room. Since it was a garage it is on slab and 3 feet lower than the rest of the house. The previous owner put n a catherdral ceiling. This ceiling has fiberglass batting and is accessible from the attic. There is a subfloor built over the slab and the slab has a plastic vapor barrier over it. 2 walls of the room are exterior walls. One of the walls was insulated properly. But the northwest facing wall always has condensation in colder weather. I cut open the sheet rock and see there is no insulation, just wood frame and sheetrock over the cinderblock. I introduced a whole room electric space heater and it tremendously helps reduce the condensation when the temp drops. But it doesn’t eliminate it entirely. When the temp drops near zero there is a small 4″ area where the wall meets the ceiling that Ice forms. I’d like to begin utilizing this room as a family room. I plan to add a gas fireplace to help with the interior condensation but before I do that I’d like to address this northwest wall. Do you think I should remove the sheetrock and insulate it? Should I put in a vapor barrier? If so, then would foam be better than fiberglass batting?

  12. Hi
    My condo complex has recently put new siding, windows and very tight insulation on our 3 story buildings. We have a two bedroom, 2 bathroom condo and fans were installed in both bathrooms that are suppose to vent to the attic. I am on the second floor and I understood that there is some sort of blockage in the pipe that leads to the fans in my bathroom. I am waking up gasping for air in the night and most recently I ended up with a very serious sinus infection that has lasted weeks. We have a natural wood burning fireplace (no insert) that we use all the time. I do not think the bathroom fan idea is terrific given the fact that we all have fireplaces and drawing the particulate matter from the fireplaces to the bedrooms cannot be a good thing. the condo complex is trying to determine what they must do to rectify this problem. Do you have any recommendations?
    With Kindest Regards,
    Donna R.

    • First, I wouldn’t necessarily connect your maladies with your house, especially the sinus infection. There’s been a lot going around this winter and, I too, am just getting over a month+ long sinus infection.

      Depending on where you live, there are specific ventilation standards for residences so that they can scientifically determine how much fresh air turnover you have. They’ll refer to this as some number of “air changes per hour”, abbreviated “ACH”. The actual number depends on number of residents in the unit and is typically computed based on the number of bedrooms. You should check with your local building official / code enforcement officer to learn what the requirements are for ventilation in your area.

      Back to your specific comment. It is very important for bathrooms to be properly ventilated, so installing bath fans in your unit is a good thing. Without proper bathroom ventilation, your unit will be prone to unhealthy levels of moisture which can lead to mold growth and promote the rotting of your building. If the pipe (duct) that runs from your bath fan out was blocked, then the fan would suck less air from your unit, rendering it less effective at flushing out the stale air. If anything, without proper ventilation, you would have worse air quality in your unit.

      You have valid concerns about the fireplaces. It is important for homes with fireplaces to have adequate fresh air to support the fire. Moreover, the fireplace needs to be designed in such a way that it will properly exhaust up the chimney and not into the unit. Fireplaces often generate a large amount of carbon monoxide, so it is especially important for the fumes to go up the chimney, not into your living space. Keep in mind that your clothes dryer and stove vent fan (if you have one) can pull many times the amount of air that the bath fan does. If running your clothes dryer hasn’t caused problems then it is highly unlikely that a bath fan would. I’m not saying it’s impossible, just unlikely.

      That said, a bath fan, especially one with a blockage, is going to have so little pull that it is unlikely to affect a properly designed fireplace. BUT – when they performed all the upgrades, they should have done a “worst case” test of the units. This test involves measuring the air pressures in the unit when all the fans are running – dryer vent, bathroom, kitchen fans, etc. This one test shows how leaky the house is and gives guidance to the amount of fresh air that should be brought in to keep you and the house healthy.

      Given your concerns, I would check with the association to determine if they had anybody actually measure the units after the upgrades. Many areas now require these types of measurements to ensure the health and safety of building occupants after the types of upgrades you mention. If you do not live in one of these areas, then I highly recommend that you hire a person to perform such tests so that you have actual numbers in hand and know how to proceed. Without hard numbers, you are just speculating, so this type of test provides invaluable information that allows you to take the next steps.

      One final comment – if you use a fireplace in your home, you must have working carbon monoxide detectors – it’s a matter of life and death. There should be several around the unit, but at the minimum, one in the room with the fireplace. Best to have one in each bedroom as well. Most building codes require them these days.

  13. I HAVE to reinsulate my attic. Because of some remodeling I have had to replace some ceiling sheetrock. We had a new roof put on and at that time installed a ridge vent. We had the usual roof vents as well as gable vents prior to the new roofing. By default I have had to get into the attic and have installed some baffles and have had to “unplug” some of the soffit vents because the junk insulation that was dumped over the 60 year old bats was plugging them. I am considering putting in Solar Guard reflective insulation under new battings as a vapor barrier where there was/is none after removing the old insulation. To much? Again there is no vapor barrier in the ceiling now.

    • Depends upon your climate. As a general rule, the colder it gets, the more important a vapor barrier is due to the risk of condensation. In more moderate climates, the current thinking is that no vapor barrier is good because it allows small amounts of moisture to easily escape through normal ventilation of the attic.

      Studies have shown that small holes in the sheetrock, like from electrical boxes and such let much more moisture through than the painted sheetrock, so I’d personally want to ensure that any holes through the sheetrock are sealed tight. BTW – if you use/install recessed lights, don’t believe the label “air tight” – they’re anything but! The only recessed light fixtures that I’ve seen that approach air-tightness are the newer LED lights that seal tightly against the sheetrock with a gasket and have no air-holes.

      Anyway, as for the reflective insulation – another important point is that if you put it under the insulation, then that shiny surface does nothing to help. You’d be just as well off with a piece of plastic dropcloth. In order for radiant barriers to work, they have to have a gap of at least 1″ or so between the shiny surface and any other building material.

  14. I’m getting bids to insulate the exteroir walls of my mater bdrm and bath which faces the north of my 73 model house. Its usually 5 to 6 degrees cooler than rest of house during the winter. I have already had new dp, low e argon filled windows installed and apprx 15 in of insulation blown up in attic. All that helped for the summer months here in N. Texas but not so much for the winter months. One contractor bid to spray foam the stud cavities from either the exterior or interior by drilling 3 holes top,middle and bottom and injecting tripolymer 105 foam. The other wants to foam the air gap between the brick and exterior sheathing using the same method as above using cfi insulsmart foam, this just doesnt sound right to me. What about the weep holes? Do you think either of these insulation practices work? Or is there a better solution to my issues. Im thinking of hiring an energy audit that you mentioned with the blower an ir test to see where my problem realy lies. Any suggestions or comments will be appreciated. Thank you for your help in advance. Jason

    • Jason,

      Given your issues, I think a professional auditor would be the way to go before investing in more upgrades, especially if they’re talking about foam filling the gap between the brick and sheathing – like you noted, there’s a reason that they’ve built with those gaps forever!
      If you do decide to go with an injected foam solution in the wall, then I strongly advise you to have the walls thermally scanned before and after to ensure that they actually filled the wall cavities. Without a test like this, you have no guarantee that they did a good job. I would further advise that you get in writing a guarantee that the wall cavities will be fully filled and that it is their responsibility to cover all costs for return trips. Ideally, the foam contractor would have their own thermal imager so they could inspect the job as they go, but you’d be really lucky for this to be the case.

      Back to your original issue – if the rest of the rooms on the north side of the house are comfortable and just master bed and bath are problems, there’s a chance that you’ve simply got inadequate heat going there. I have a friend with exactly this problem and we’ve had to work hard to try to get more hot air supplied up there from the furnace. If you have baseboard heat, that’s another story. Sometimes, you’re best off getting a mini-split heat pump just to service the master BR – I did this in my own home and don’t think I could live in the house without it! Being able to adjust the BR to exactly the temperature you want is an amazing luxury.

      Hope these tips help.

      • Thank you for the quick response, the mstr bdrm and bath are the only rooms on the north end of house and we have centeral heat and air electric heat strips 15 kw. Planning on heatpump on next change out. Thank you again Ted, I will be getting an audit scheduled soon. What should I expect to pay for such a service?

      • A quality energy audit would run $350-$500 for a whole-house review, assuming an average sized home.
        When I took on clients with issues like yours, I would offer a troubleshooting visit at an hourly rate and that would usually run $200-$300.

  15. I totally agree with you, public education is crucial but I would add not only in your field but in many others too. Can you imagine when it’s a health issue? Do you know that many doctors don’t take in account the dynamic of the whole organism when they act on it ? Same thing in psychology and I bet in many other domains. The thing is if we don’t take in our hands our own file chances are nobody will. And this is very disappointing because the only thing I want is TRUST someone who’s responsibility is to do a job I can’t do without having before hand to spend hours like I did reading about it because obviously all those guys are missing obvious points I SEE and I know nothing about their work. Reading your articles make me realize how much I am ignorant. Now I am going to have to make an inventory of the past renovation I made and the one I was intending to do.

    VENTILATION of a roof made 3 years ago.

    In reference to an above comment made 2 days ago by Jon who says:
    “They ….. overlooked the fact that our house doesn’t have soffits. I had no idea about this kind of construction/venting and how the venting needed to be 50% soffit 50% ridge vent. When I told the roofer that the warranty for the singles would be voided without proper ventilation, he claimed that he thought we already had soffits? The entire job was complete and no one on the crew questioned our lack of soffits? They had to come out and add edge vents to the entire perimeter of the roof ”

    The question of the roof scares me because I also trusted a well-known company who I am sure didn’t do their job correctly if it’s true that when you don’t have soffits it’s important to put edge vents to protect the integrity of the roof. And from what I can see they didn’t : ( And it did also cost me
    $ 10,000.00 for a security I didn’t get.

    Any recommendation to ventilate my roof properly? Should I approach the roofing company about this?

    On the other hand the attic isn’t YET, thank God!!, isolated. I don’t know Ted if there’s a relation between what I just said and the ventilation of the roof but maybe it does. The condition of the attic is okay because it’s an old house (1953) and air seems to circulate in it because of the cracks. Also we still have the equivalent in wood of soffits with opening in them (like in the old time). I know we’re suppose to replace wood by appropriate soffits. We didn’t yet.

    In any case I made an evaluation of the energetic efficiency of my house and the independant company recommended to isolate the attic. This company will come after to check if it was properly done. That said you raised my level of awareness and now I am going to make sure that the company who will isolate my attic with this foam product will do it in a proper manner. That said I feel now insecure because I am afraid to miss something obvious but a least now, thanks to you, I am less ignorant.

    I’ll have to move now to the heating system section to post a note since when I started reading your articles It was to read only about replacing a heating system and adding, while we’re at it, a heat pomp. And then I migrated to this topic.

    Thank you Ted !


    • Thank you for your discussions. When I got started in this, I was doing one-on-one consultations and soon realized that the problems kept repeating themselves. So I’m glad my posts are helping people all over to avoid or remedy their issues. Sharing your stories helps to show others that these problems are universal and, like you said, unfortunately, we have to take matters into our own hands and ensure that the work being done is appropriate.
      If you take good care about sealing the attic floor, the attic ventilation issues become far less important. I’ve seen perfectly ventilated roofs with rotten sheathing because of lack of bath ventilation or similar issues that allow lots of moisture from the house build up in the attic. I’ve also seen very poorly ventilated roofs last for decades! The key is to know what the big factors are and address those.
      In your case, as you noted, the key is to isolate the attic. The easiest way is to get a coating of foam over the entire attic floor combined with ensuring that the baths are ventilated right up through the roof and the attic access has a good seal. If you do this then there’s very little chance of moisture buildup if you have any attic ventilation.
      If you have the budget for it, then you’ll want to use several inches of foam on the attic floor, to bring it up to code levels, but it gets expensive fast. An alternative is to use a relatively thin coating of foam – 1/2″ to 1″, coating the entire floor and joists (this air seals and greatly reduces thermal loss through the beams). Once you’re sure the foam job is good and is really air tight, then you insulate the rest of the way with another insulation product, like blown in cellulose. This is assuming that you’re in a coldish climate. Things turn around if you’re in a hot, humid climate like Florida.
      If you have a heating/cooling system with ducts in the attic, you have to take considerable care to seal that up. Since it’s under pressure, it can blow out lots of humid air and ruin your roof. These days, many areas require duct testing to ensure the system is tight. The company that did your energy evaluation should be able to do those tests as well.
      Good luck with your projects!

      • So awesome how you take in account many variables at the same time, including the financial’s one to make sure you are really helping me look into fundamentals.

        The thing I retained from you is the importance of taking my time because anything I do without having a minimum of a good comprehension of the way things are linked together dynamical speaking (= big picture) can end up in hurting my old house instead of serving it.

        The thing is I haven’t done anything for decades but thank God the integrity of my house is still okay. Still I have now to address everything at the same time with a limited budget. And I find it hard to prioritize.

        I also retained from you that when something works we have to be careful when we touch it to “improve it” because by doing so we might introduce a critical problem instead of helping positively the house. And the attic in this regard is a perfect illustration of what can happened if we’re not careful with the way we will handle it’s issues.

        Every one of your recommendations regarding the isolation of the attic, on top of being greatly appreciated, makes totally sense for me.

        By the way the heating system with ducts is located in the basement, which basement isn’t finished (but this is another topic I won’t be able to address before a while but I already read some of the things you had to say about it. ONE issue at a time 🙂

        Last question in this department if you allow me 🙂

        Like earlier mentioned my roof was redone about 3 years ago. I understand that the fact that I don’t have soffits (beside old wood’s one with a couple of opening in them) should have been take into account in some way by the Installation of edge vents to protect the new roof ? I am a little bet confused because I don’t have a clear picture between the dynamic of the roof (top) and the attic and the house. Should I take care of this (hoping my roof wasn’t affected by the lack of edge vents).

        Should I prioritize the installation of modern soffits rather than keeping the old wood’s ones?
        I went to the attic this morning and you could see in the dark light where there’s opening in the wood soffits.

        Looking at my atttic wasn’t the same experience than before. Now I feel more in control thanks to your explanations.

        Thank you Ted,


        P.s. I live in the North Pole not far from this very known neighbor of mine Mr. Claus 🙂 So yes this weather’s variable need to be taken into consideration when it comes to the isolation of the attic’s floor.

      • Yes, big picture is truly important. A lot of harm has been done with good intents by forgetting about unintended consequences.
        As you note, prioritization is truly difficult because everything seems important. Your health is #1. Then your home’s health. Then efficiency and comfort. Often you get benefits together which is good! But sometimes, things people do in the name of efficiency can hurt. Like tightening the house air-tight without adding supplemental ventilation for fresh air.
        I’m glad your ducts are in the basement – that simplifies things in the attic.
        On to your question!
        I need to ask you a question or two before making suggestions. Sorry if you already answered these in a previous message, I just want to get it all in one place. This will help others to understand the thought process.
        – When you replaced your roof, did you replace all the wood under the shingles? If so, what happened? Did the roof rot out from underneath (the attic side) or was something else wrong with it?
        – Was the wood black or moldy when you looked from the attic?
        – When you redid the roof, did they add a ridge vent or was there one there before?
        – Is there any other venting in the attic, like louvered gable vents at the end walls?

        Let’s say for example, that your roof sheathing had rotted out before due to moisture in the attic and that you had gable vents and no ridge vents. This was normal construction a few decades ago and it worked fine for most homes. But if moisture caused your roof to rot, something is wrong. In a cold climate, that moisture is almost certain to have come from inside the house, though sometimes it starts at a wet basement, goes up the walls, and into the attic.

        So let’s go from here and answer the questions about your roof.

      • Thanks so much for the info!

        This is a question regarding materials. Through all of the horror stories and research I have ran across in having our roof re-shingled and our insulation upgraded I have wondered why batting insulation AND wood or osb roof sheathing are used at all. I realize money is an issue. I too do not have much. However, seems like “roofs rotting out” is a common problem. Why is wood the standard roof sheathing if it has a tendency to “rot out” or why isn’t it standard practice for roof sheathing to at least have mold and moisture resistant paint underneath to prevent this from happening in the first place? Are you aware of a roof decking material that will not rot? There are materials for the outside of the house such as Hardy plank (not a fan of this look however) that are rot resistant. Why not roof decking?

        Thank you for all of your advice and tips!

      • As for roofing material – it’s most likely price and availability. The switch from plywood to OSB or flake-board is a good example. If they can save a few dollars per sheet, that goes right to the builder’s bottom line. This is in spite of the fact that OSB is a horrible material for use in wet conditions! Plywood is actually a much more moisture tolerant building material.
        There are millions of homes with wood roofs that don’t rot out, so it’s not that they’re prone to it. It’s just that a variety of factors are conspiring to make moisture problems worse than ever.
        I talk about unintended consequences a lot. Here’s one. Older homes were much leakier and had minimal attic insulation so they were drafty and cost a lot to heat. But those leaks and drafts helped to flush out moisture from the home. Remember when we were young and we’d get nose bleeds every winter from the dry air? The air was so dry in our homes that there was little moisture going up to the attic to rot the roof.
        In addition, with the little bit of insulation homes had in the attic floor, a lot of heat escaped up to the attic. This heat reduced the risk of condensation in the attic. Another factor that helped prevent roof rot.
        Today, we have tight houses, which are much more comfortable and energy efficient. But that means there is a lot more moisture trapped in the house. When that moisture goes up to the well insulated attic, it finds a very cold space and condenses on the surfaces up there.
        Worse, because of the dry-air syndrome, builders installed a lot of high output humidifiers that dumped gallons of moisture into the home every day. This really speeds up mold growth and rot problems. Tight homes don’t need added humidity. Put all these factors together and you end up with the problems we see today.
        I should have mentioned the whole home humidifiers before. If anybody reading this has moisture problems and is using a humidifier, turn it off immediately! They are absolutely destructive in a modern home and truly shouldn’t be allowed.

    • Hi Miche–FYI, our house doesn’t have soffit vents because we don’t have any eves at all. The roof is a very steep pitch and meets the bottom walls of the house right at the gutter. Many roofing companies are installing ridge vents but in order to have a ridge vent work properly, you need to have soffit vents at the bottom of the eves or in our case, have edge vents installed at the bottom of the roof line. Here is a link to what I am talking about.

      I really hope this system works. According to everything I have read, all the people that I have talked to, and many many hours of research (bitter bitter research) along with the thick r31 thermasheath rigid foam insulation (foil backed on both sides as a vapor barrier) installed with a 2″ gap in between the roof decking and fingers crossed that working in the wet humid Seattle weather over the next couple of months on this will not be too late to create a problem. I feel like if we did this job in the hot summer, I wouldn’t be facing possible issues of moisture problems right now. I am trying to be preventative in any issues happening as we continue to finish the job.

      To Ted (again thanks for you expertise!). To clarify a bit more about our attic space, it is actually a converted attic space. We are trying to make it a properly conditioned attic space with cathedral ceilings. The walls and ceilings that were ripped out were made of a thin plywood with wood wool insulation that was falling apart and not evenly covering everything anyway, The roofing shingles that we just had replaced continually grew moss and was the only house on the block that never had frost or snow on it in the winter. I know that older homes need to breath but I feel like the attic not being properly insulated (with a moisture resistant insulation) nor properly dry walled (plaster and lath on the lower floor) with leaky knee walls that led to the moss formation and the roof needing to be replaced in a shorter amount of time than desired. The new ridge vent that was installed (completely closed dead space before this vent was installed) along with the later added edge vents are the reasons that I am trying to do every single thing that I can to make sure that this job is done properly as to not have someone approach us later saying “Well, if you would have done “THIS”, you wouldn’t have that problems that you have now!” What is killing me is, only time will tell if this system is going to work and not have any problems in the future.

      I am still wondering if the best protocol in the partially insulated space would be to keep a dehumidifier running to take any possible accumulation of condensation (from inevitable leakage from downstairs heat or moisture) out of the air in the top rooms/converted attic until we can finish the job. We have fans running and are blocking off the stairwell to the best of our ability.

      Thank you for your time and I hope that the space description made sense. I would attach pictures but I can’t figure out how to do this.


      • Tracy – thanks for sharing that Certainteed link – that looks like a great system!
        For photos, I think you’d have to make an album somewhere else (like Google photos) and share link to that. Like this for example:

        The dehumidifier might not be a bad thing to use since you know it worked before. And if you kept the humidity down to a moderate level, it would certainly help keep the exposed roof sheathing in better shape while you can’t work on it. They’re somewhat expensive to run because they use a fair amount of energy, but it’s a lot cheaper than replacing a rotten roof!

        BTW – I’m not convinced the moss on the roof is due to your construction / lack of insulation etc. Usually mossy roofs are those that stay humid and cool due to shading. Is it possible that your roof is more shaded than the others in the neighborhood that don’t have moss? Are there other conditions that might contribute to your shingles being damp? Do they all have the same roofing materials as you? Wood shingles grow good moss around here, especially down by the Delaware river where they’re in the shade and get morning fog often – our closest simulation to Seattle weather 🙂

  16. Coming back to this – regarding unintended consequences of tight houses, ours got to the point where when we lit a fire, the basement filled with smoke. What?
    Well .. the fireplace had to draw from somewhere, and one of the biggest remaining holes in the house was the boiler flue. Where did it exit the house? Right at the top of the chimney, right next to the fireplace flue. So the fireplace was sending smoke up the chimney, and the boiler flue was drawing it back down in the the basement. (never mind the backdrafting, etc… we now have a sealed combustion boiler… solved that problem the expensive way!)

  17. Thank you so much for such a wonderful site!

    I have to say, as an artist and homeowner, I feel completely bitter that I have had to start to think like a contractor. I have learned more about what not to do in our 1930’s 1,800 sqft plaster and lath two story home than what “to do”. No one seems to know the right answer and money spent on “professionals” don’t usually go hand in hand. We just spent $10,300.00 on re-shingling our roof. The roof decking is osb, in decent shape so they didn’t replace it. New under layment was placed underneath high end designer shingles. They added a ridge vent, removed all of the vents at the mid roof line and overlooked the fact that our house doesn’t have soffits. I had no idea about this kind of construction/venting and how the venting needed to be 50% soffit 50% ridge vent. When I told the roofer that the warranty for the singles would be voided without proper ventilation, he claimed that he thought we already had soffits? The entire job was complete and no one on the crew questioned our lack of soffits? They had to come out and add edge vents to the entire perimeter of the roof. $10,000.00 doesn’t buy professionalism and I still had to act like a sleuth!

    Onto my question…We have a livable attic space that we are “upgrading”. We tore out the ceiling and walls, took out the wood wool that was falling apart and plan insulating our cathedral ceiling with thermasheath r31 rigid foam insulation (4-1/2″) with foil on both sides in between each rafter bay, extending all the way down, pass the knee wall to the floor. (there is a 2″ gap allowance in between the insulation and the roof decking that should allow the air from the retrofitted “soffits” (edge vent) to the ridge vent to escape, HOPEFULLY. My husband added wood to the rafters to extend them longer to allow for the thick foam insulation) Because we spent all of our money on the roof, our plans and time were delayed until the colder months. We live in Seattle, WA. I tried to block the stairwell going up to our two upstairs rooms(attic space) where the insulation is being installed but we waited too late into the cold months and warm air from the downstairs ended up condensing on the roof decking (on exposed nails and a metal patch). We rented a heavy duty de-humidifier and for two days and ran fans and a heater on low inside of the rooms to dry out the roof decking. The job is not finished, only 1/2 of the space is insulated. We had to return the dehumidifier to Home depot, it was getting expensive. Do you have a good idea for us in how to continue this project on a budget, doing it in our spare time, maybe waiting until summer without ruining the wood or causing moisture/mold damage? Should we be constantly running a dehumidifier until we can finish the insulation and drywall? Is there a temperature consistency/dewpoint that we should monitor in the space until the work is complete and done? PLEASE HELP! I don’t want to ruin our home and I don’t know what to do nor does anyone else I have talked to. We simply don’t have the money to hire someone to do the work right now and we have very little spare time because we run our own business. Any advise on this epic reply? Thank you so much for your time!

    • I feel your pain. It’s largely the reason I got into the home energy/building science consulting business years ago. Too many unqualified contractors forcing homeowners to learn how to do things right or get stuck with sub-par or even dangerous workmanship. Frankly, it’s very disheartening.
      It does sound like you’ve done your research well. A good gap from soffit to ridge behind the foam should do a good job of ventilating that space – do your best to air seal the edges where the foam board gets installed so that the moist air can’t sneak in and condense when it hits a cold surface. You should be good once the ceiling is installed as long as you keep it intact (no recessed lights or other holes in the ceiling other than maybe power wires going to fixtures).

      As for your problem at hand – have you tried taping plastic sheeting over the opening up to the attic? You do have to be careful to seal it completely to minimize the amount of air from the house that can get up there. And if there’s any other sources of interior warm air that might get up there, do your best to seal that off. Since you’ve got the soffit and ridge vents, that should take care of most of the remaining moisture that does get in there.

      Regarding nails getting condensation on them – I wouldn’t worry to much about them. They’re conducting heat/cold from the outside very effectively so it’s almost impossible to prevent. And the metal patch – what is that? Is that like sheet metal that replaced some of the roof wood? if so, that too will likely be hard to prevent from condensation unless you can prevent any moisture from coming in contact with it. Depending on the size, you could temporarily mount a sheet of foam board over the patch -it doesn’t have to be the really thick stuff, maybe 1″ thick should do. You could run a bead of canned foam around the perimeter and squish the foam board right over it. This will insulate the patch and minimize the moisture that can reach it.
      If the attic is left open for ventilation (soffit and ridge vents) and you seal it off from the rest of the house and insulate the really cold patches, you have a good chance of combating adverse moisture buildup. You shouldn’t have to run a dehumidifier unless you missed a big hole where warm, humid house air is getting up there. A little humidity won’t hurt things as long as it gets a chance to dry and it isn’t soaking wet. Usually, when the sun shines on the roof, it should heat up enough to dry it out. Granted, Seattle in the winter doesn’t get great sun, and the natural humidity doesn’t help.
      I would check it out after a few days of being sealed up to ensure that it’s staying reasonably dry. If it isn’t, look for other sources of moisture that could be contributing to the dampness.
      Feel free to drop more questions as you progress.

      • Wow! Thank you so much for getting back to us so quickly:) My father in law and husband (I am actually Jon’s wife Tracy commenting!) are quite impressed with how quick and and in depth you were with answering my questions. This has all been such a guessing game and to have a professional give us some advise, well…it’s worth it’s weight in gold. The internet has really helped but boy, there is so much information out there and it takes reading some of the same tips, do’s and don’ts over and over to find out what even qualifies as a valid question. Regarding condensation, like me, if anyone is wondering how long it can take to accumulate on the roof decking if you delay your insulation project, well…it can happen immediately, with the first cold night and warm house. The metal patch I was speaking of that gathered quite a bit of condensation was a cover over one of the former box vents. The only reason we noticed the condensation on the metal was due to the underlayment that was ripped around the edge exposing the patch above the cut wood decking. Not sure why the under layment was ripped, maybe someone forgot to mark the hole and accidentally stepped through it while laying the shingles? I am glad that we are re-insulating because this could have been a potential problem. Thank you for explaining how to patch it to lessen the potential for condensation to form.

        There is a door and stairwell that go up to our attic which was a conditioned living space. It seems more like a second story rather than attic due to the narrow stairwell with a window at the bottom. There is a hallway with a room on either side and a window in each room. One of the rooms has the ceiling and walls ripped out, our new insulation on most of the ceiling, all the way to the floor (like an A frame, no dormer) and no insulation on the end wall that has a window. The wall on the other side of the insulated room (same wall that shares the hallway) is open at the top exposing the dead space above the hall and other 1/2 of the upstairs room that is yet to be freshly insulated. The other room still has walls and a low ceiling but the knee wall has a door that is quite air permeable and the walls are in bad shape with cracks, holes, and poor construction. (like a high school student found a stack of plywood and made “walls” and a “ceiling”.) The disintegrating wood wool is still in the ceiling on this side but it isn’t covering everything very well from what we can see. So, it is quite open to warm air hitting the roof decking and exposed wood wool insulation. We have the door at the bottom of the stairs blocked with a piece of 2 inch foam but our ceilings and walls are plaster and lath, no insulation in between them. So, hopefully my epic description will help answer if you think we should run a little heater to keep it dry (seems like a bad idea), fans, or a dehumidifier upstairs with the probability of some warm air most likely forming onto the roof decking before we can finish the project? The dehumidifier really seemed to dry things out overnight before we insulated the one 1/2 of the attic. It will probably be another month before we can do the rest. It is a busy time of year with our home business!

        Thanks so much for your expertise, time, and attention to detail. I will make sure to “pay it forward”!
        Take care and happy holidays,

      • So if I’m understanding correctly, this is the entire upstairs of the house? I’m confused about the roof ventilation. You noted the soffit and ridge vents – so I was assuming the upstairs was directly exposed to that ventilation. Is that true?
        And, since there’s so much demolition up there, a lot of the warm air from inside the house can get up there?
        As for the condensation – the sheet metal section will have condensation immediately but it won’t be a real concern. It might rust a bit but in the next couple of months, it’s not going to crumble to dust. Plus, hopefully they used some metal that’s water resistant. I’d be more concerned about the liquid water that drips off of it. So anyway, take a few minutes and put that insulated patch on it.
        The bigger concern is the wood which can rot and also provides a base for mold to grow. Can you tell how wet it’s getting? Ignoring the nails, which will get drops of condensation on them.
        In Seattle, you may be dealing with a Sissiphean task. The outdoor air during the day may be very humid. At night, the upstairs space will cool down very quickly leading to the condensation. Even out here in PA, some days my garage gets filled with condensation when we get a temporary warm front that brings humid air in. Everything in the garage is cold and the humid air condenses immediately, rusting all my tools. So you’re dealing with a real conundrum. If it were dry and cold, you probably would have a lot less of a problem. Not knowing your exact situation, I can’t tell whether it’s moisture from inside the house or outside air that’s the bigger problem. The best you can do is seal up the biggest holes, then monitor the situation. Big fans will help to move air and allow moisture to evaporate as conditions allow. If the space really is open to the outside due to venting, then a heater will be a huge waste of money and it will cause the mold to grow much faster, so don’t do that.
        If you keep a handle on it, minimize extra moisture load in the space, towel down any areas that are actually wet and run fans, you’ll probably be able to limp through the next couple of months. But it’s a dicey game to play – you really want to keep an eye on it and if it seems things are getting out of control (i.e. wet dripping from the roof deck or signs of mold growth) you’ll be forced to jump on it immediately. It’s still possible that you’ll get some slight mold growth in that period. Keep your fingers crossed and finish the project as soon as possible!

  18. Pingback: Bad Advice: What People Say About Installing Spray Foam Insulation | Spray Foam Solutions

  19. Excellent post! My parents are looking at insulating their turn on the (last) century farm house. It has 3m walls, cement ceiling and corrugated tin roof with 1 working chimney, multiple vents and open door way entrance (and as a result lots of “wildlife” up there). The house gets quite chilly in the winter when the temperature drops to 0ºC. They are favouring the spray foam option and I was wondering what you think about that?

    • Wow, that’s a tough one. Honestly, it sounds too complicated for a recommendation without being there to evaluate the nuances of the design. I’d also warn that if you ask a professional insulator, many will sell you on their solution whether it’s good for the house or not. Your parents could waste a lot of money on foam and have it make a minimal improvement or worse, cause a problem elsewhere in the house.

      Your best bet would be to get a comprehensive overview and recommendations from an independent home energy consultant. For about $500US, it’s a great investment. You want someone who doesn’t have a stake in selling you a specific solution and will be honest and direct with you.

      Good luck! Sorry I can’t give you more advice.

  20. I ran into something like this. Sealed & insulated the attic, and then had a new roof put on. The roof plan was to do a ridge vent and “retrofitted’ soffit vents, something called edge vent. Well… the attic insulators dense-packed the cellulose down into the crannies where the ridge vents were supposed to be venting. Needless to say they didn’t draw air very well. 😦 I went up with a stick and a shop vac and tried to get it out of there, but it’s nigh impossible.

    Is there any way to actually measure attic ventilation?

    • I can’t think of a good way to measure ventilation that is reasonable given the large areas involved. If you had an attic that just had gable vents, you could measure pressures at each vent and combine that with the opening area to compute air flow but the measurement would vary tremendously with wind and temperature so I don’t think it would be terribly useful.
      In the situation you ran into, you might be able to tape plastic under the attic hatch (inside the conditioned space of the house), then use a manometer to measure the pressure there. With a properly sealed hatch, you should get zero but chances are, you’d have a negative pressure relative to the house, indicating air flow from the house to the attic. There are techniques you could use to quantify the actual air flow at that location, but again, it’s imperfect since there are usually so many places that air can move from the house to the attic.

  21. Have you ever worked with “Retrofoam”? We have a house built in 1979 with a master bedroom upstairs loft area and it only had an inch of styrofoam in the cathedral ceiling for insulation and batting in the walls. We’ve had all sorts of problems with the AC maintaining temperature and high humidity, so we had Retrofoam injected into our walls and ceiling, but the problem didn’t resolve. After we had the AC unit fixed, as it was also part of the problem, it’s maintaining temp, but we still have a humidity problem. Prior to the foam we had humidity around the same % and were running a dehumidifier which increased the temp of the space. I’m just baffled that we can’t figure out how to make the AC unit do it’s job and keep the humidity level down. And now, I’m not so sure we didn’t just make the situation worse. Any advice?

    • Unfortunately, I haven’t. I investigated it and talked with an installer a number of years ago and it looked quite interesting but opted not to go with it because the installers in our area didn’t seem reliable/experienced with it.
      The one big problem I have with any injected product, whether it be foam or other product is that you’re at the mercy of the installer to do a good job unless you validate the job with an infrared camera. A friend of mine had a foam job done in his walls that was a total dud – when I looked at it using IR, you could see that the foam just dribbled down the wall and didn’t fill the cavities.

      I mention this because it’s very hard to know what’s going on inside of the walls without a test like combining a blower door and IR camera. It costs a few hundred dollars, but it’s well worth the expense because otherwise you’re just guessing and can spend thousands of dollars trying things that may or may not work.

      Humidity problems are a dead giveaway that you have a leaky house. A blower door test with IR scan should show you where the leaks are. It might be something systemic in the way the house is built or it could be something as simple as a bad duct in your attic which is the cause of the worst problems I have seen.

      So my advice, is find a good energy auditor locally who has experience in troubleshooting using IR and a blower door. You may have to interview a few people to find someone who isn’t a “production” energy auditor. These days, there are a lot of people just doing cut-rate energy audits but who really don’t understand building science and troubleshooting. You want a trouble-shooter. Explain your problem and listen carefully to their reply. If they seem to have a generic cook-book, they’re probably not a troubleshooter. If they can clearly explain what causes your type of problem, it probably means they’ve got some experience. Make sure they use a blower door and an IR camera. If they say they don’t need one or the other, send them packing!

      Good luck. Please let me know how it goes. I think your problem is very solvable.

  22. Thanks Ted!
    Your tips on attic insulation are very helpful. I’ve been researching a variety of things that can be done to increase energy efficiency while designing an addition. One topic is geothermal energy for the home. After speaking to several geothermal professionals/installers, one thing they all recommended was to first take a hard look at the energy efficiency of the existing home. And, consider a conditioned attic space.

    It appears to be an effective method of reducing the costs of geothermal installation; better insulated attic and home overall calls for a smaller and less expensive geothermal system. Further research suggests the attic is a great place to start with respect to energy efficiency. Your tips are extremely helpful in that regard. Again, thanks for the detailed info and photos.

    • Yep, energy efficiency is definitely the first thing to look at if you’re looking into geothermal. One thing that is often overlooked is that a more efficient home is also more comfortable because the temperature is more even. Also, as you noted, it helps reduce the cost of geothermal. More comfortable and less expensive is a good thing!

      Good luck with your projects 🙂

  23. Hi, I would be interested in your opinion regarding adding exterior foam to walls. I worked as a carpenter up to15 years ago and am a certified R-2000 builder. My own home (20yrs) is r-28 walls, strapped with 2×3 to protect the vb and provide a chase with a hrv the home has performed perfectly even at -55f temperatures. I am planing to build a smaller home for retirement and because there are more windows in smaller walls, the many headers, jacks and corners, I am considering adding exterior foam. Because of my background, I am having trouble with the idea of omitting thr VB. We use to omit the tape at the top of the walls to allow the typecast to breath into the vented soffit. Can the interior walls be build both foam and VB and the top exterior be vented with 1″ vent plugs to vent into the soffit. Thank you

    • With your background, you should be writing these articles! 🙂
      It sounds like you’re working in extreme environments up there. In such cases, the risk of condensation is much higher than down here where things are milder.
      The fundamental theory that guides recommendations is to ensure that warmer, moist air from inside the house can’t come in contact with any surface cold enough to lead to condensation. With enough exterior foam, you should be able to maintain inner surfaces at warm enough temperatures (roughly 50F), but you clearly have to be very careful in your construction. With your background, I’m sure there’s nothing new here.
      The “gotcha” that sometimes bites even experienced builders is adding too much insulation inside of the exterior insulation because that insulates the wall cavity from the warmth of the house. In doing so, it can allow the surface between the exterior foam and the interior insulation (usually the exterior sheathing and the 2x studs) to get too cold. That’s where the serious VB comes in to minimize the moisture that gets into the wall cavity. Problem is, with a tight exterior AND a tight interior, you’ve got the dreaded double VB situation that can lead to real problems. If any moisture gets in there, it can get trapped and build up over time.
      Given the severe temperatures you’re dealing with I’d be really careful. Read through for their info on cold climate considerations. And be very skeptical about any solution that needs to be ‘perfect’ in order to work.

      Sorry that this isn’t a more definitive answer to your question. I hope there are a few kernels of information that you can use.

  24. Fireplaces or stoves should have OUTSIDE AIR for COMBUSTION. Many stoves offer this as an “optional” kit and fireplaces can be retrofitted (good luck finding someone who understands it much less do it).

    • Great point. In the “old days” with leaky homes, people didn’t worry about it. Now that we’re tightening up millions of those leaky old houses, outside combustion air becomes necessary. Fortunately, new home building codes require this but as you noted, there seem to be a lot of contractors inexperienced with this. Our best bet is educating the consumer so they can insist on proper combustion air.

  25. Great post, many people don’t quite know what goes in to insulating a home properly, and its a real shame that some companies out there are more than happy to charge people for a poor quality job – look out for these people!

    • Thanks for the comment. If there are ever any warnings you have for people, please pass them along. I’m doing my best to help educate the public but it helps to hear from those of you doing the work because you guys are often fixing problems that others have caused. Send photos of the big disasters you see 🙂

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