If you have any questions you want answered, feel free to drop me a note. If you’ve got a question, chances are, there are lots of others out there with the same question. So ask away!
Note: all comments are moderated unless I’ve approved one of your previous comments. Almost everybody gets thrown off by this, but I moderate comments to avoid spammers. The downside of this is that you won’t see your comments post until I’ve had a chance to review and approve them. Sometimes this can take days (sorry!) Thanks for your patience.
Ted's Energy Tips 
Your web site is so informative!
I am assisting a client to convert an unconditioned space on the 3rd Flr. of an old victorian house in Brooklyn into a habitable space and I’m a bit uncertain in regards to the insulation. The space has 2 interconnecting gables plus a corner turret. We intend to install 5 1/2″ th. R-38 closed-cell spray insulation at the existing 5-7/8″ roof rafters. However, I could use a bit of advice as follows:
I’d like to use batt insulation w/ a vapor barrier at the existing 2 x 4 wall framing at the gables and turret to save some money. Or, should that insulation be the closed-cell spray, too?
For structural stability, we intend to have new tie rafters / a flat ceiling (w/ recessed lighting) towards the top of the main gable. I am suggesting R-19 + R-30 batt insulation at these tie rafters along with vents above at each end of that main gable. There will be a Mitsubishi split hvac system for this floor (with has the primary bath), but no dehumidifier. My 1st question is, should we instead just extend the spray insulation w/i the rafters to the ridge and not have insulation at the rafter ties nor gable vents?
Also, The turret cone interior structure rises 11 ft. above the finish ceiling. My 2nd question is, should the spray insulation follow the turret framing or should I only have R-19+ R-30 batt insulation at the finished ceiling? I hope to have a new continuous eave vent for the turret.
Any feedback would be appreciated!
Thanks Denise. For somewhat complex structures like this I’d want to foam everything so that you can maintain consistent and continuous insulation and air barriers. I’ve see hybrid systems like you describe and they can go horribly awry.
You might also want to look into flush mount LED fixtures that look like recessed lights. Recessed lights are often the source of moisture problems, even with foam, even those rated as air tight. The flush LED lights eliminate those problems and are super efficient as well.
Cheers
Ted,
I’m getting siding replaced on my +/- century old house. Right now is has aluminum siding over old asbestos shingle siding. My contractor will obviously do whatever we want, but he is strongly recommending just installing new siding over the asbestos. I know this is a common practice, but I’ve also read that it can cause moisture issues related to the house breathing. That being said, we’re replacing aluminum siding with Smartside, so I’d think the breathability would be improving anyway. Another thing to factor in is that the wall cavities are not insulated, and removing the asbestos would just decrease the r-value of the walls further. I don’t mind dropping a few thousand to remove the asbestos if it is the best thing to do; what do you recommend? If we do remove it, I would probably go back with a layer of 3/4″ foam board between the decking and the siding. Thanks.
Most people do recommend leaving asbestos siding in place since asbestos is only a danger if the fibers are “let loose” – so removing the siding can be opening up a can of worms.
It’s good that you’re concerned about moisture. As you noted, if the new siding has more ventilation than the aluminum, you shouldn’t create any new problems. Even if it didn’t, chances are that no moisture problems would arise since the old asbestos siding probably has numerous layers of paint on it forming a pretty moisture-tight siding already.
Note that you shouldn’t worry about decreasing the R-value if you remove the asbestos siding – it’s basically an R-0 material! OTOH, it’s probably helping to keep your walls somewhat more air-tight which often makes a as much a difference as insulation. Overall – removing the siding won’t have much positive effects.
As you noted, if you do remove it, then adding some foam board could be beneficial, substantially improving the R-value of your uninsulated walls. If I were in your shoes, I’d look at the potential savings from adding the insulation as well as the added expense of removing the siding and installing the insulation. I know it’s often more than a financial issue, but that’s a start. For example, when I remodeled my house, I added 2″ foam board under my siding which made the walls much more air tight as well as greatly increasing the R-value. But, I was also replacing the windows and had to take that 2″ into account and get extended jambs for all the windows. It was quite a project but I’m happy I did it.
Cheers and good luck on your project!
We recently had new celluose insulation installed in our home along with having our ducts sealed with Aeroseal and our attic flooring sealed up. Next day we immediately noticed a smell. The odor smells like newspaper that got hot. Note that we live in Phoenix, AZ and its summer time now. The contractor could not find the problem, so we hired another expert. This new company sucked out the new insulation, checked all the flooring upstairs for problems and sealed all around the air handler, which is located in a closet on my 2nd floor. He also went up in the attic and sealed where the air handler is. We are STILL noticing a faint smell. Now he wants to install a ERV, but we are hesitant because we still have a faint odor. Can you please help! We have been sleeping downstairs on our first floor on sofas for 2 1/2 months now and the stress of this whole situation is effecting my health. By the way, the company that makes the celluose insulation come out and g tested it and said it was not off gassing. But to me it sure smells like it is.
It sounds like you have done the right thing – sealing the ducts and air handler. One question – did anyone do a blower door test and thermal camera inspection? It sounds like there is still an air leak somewhere. You can spend a lot of time and money having people try random things to fix it but if you attack it scientifically, you have a much better chance of finding the source.
Look for an energy auditor who is experienced at trouble shooting.
Good luck! Let me know if you find the problem.
Hi Ted. I am eliminating an outside door. I have vinyl siding. The weather is cold winters and hot summers(Chicago). Can I use visqueen as a vapor barrier? I do not want to buy a roll of Tyvek for one opening. Thanks!
I always defer to the local code enforcement officer for questions like this. I wouldn’t want to give you advice that later prevented you from selling your house or cause problems.
Ted,
Thanks for your excellent blog, which I recently found.
I have a house which is a pole barn type of construction, rurally located in a cold area. The house had cathedral ceilings throughout, but I have lowered them, leaving the original ceiling (above) intact. The original insulation is unvented R19 batts over drywall.
I recently replaced the roof with metal, and replaced any OSB sheathing damaged by mold. I missed the opportunity to put exterior foam. I am now planning on pulling down the (now hidden) cathedral ceilings to remove all fiberglass, and will fill the bays with polyiso board, then add more on the rafters to reach my R goal and eliminate bridging. The “attic” between the roof and the lowered ceiling will remain part of the envelope, and nothing under the roof sheathing is or will be vented. Great care will be made to ensure air sealing at the roof.
The house is rural, and has no air conditioning. It is heated only with a wood stove.
Two questions:
Any issues that you see with this plan? (Feel free to mention code issues if you want, but I am looking for practicalities, and code is somewhat optional in my context).
Any value to putting Kraft-faced R-19 on the lowered ceiling, to “hold the heat down” where I live, rather than letting it rise into the attic?
Thanks in advance for any suggestions you have.
My first question is what caused the water damage to the OSB? Hopefully you found the source of the problem and fixed it because problems like that are a red flag. I’m always afraid of fixing symptoms before problems….
If I’m reading this right, it sounds like you’ll have a “dead air space” above the polyiso insulation and below the roof. Even with careful air sealing, spaces like that are extremely susceptible to condensation since they’re cold and there’s no place for any moisture to go that might get up there. As soon as moisture touches the cold roof, it will condense. If it can’t escape, it will build up and eventually something will rot out.
I’d strongly encourage you to do something that would help flush air through the little space under the roof but above the insulation. Soffit/ridge vents could save you a lot of heartache (and money) in the long run. Barring that, I would fear that it’s not a matter of if but rather a matter of when your roof will rot out.
Yes, valid question. Several causes that I believe in combination caused the mold / rot.
Leaking roof, heavy rains came through. It was very poor metal, poorly installed. It is all new now.
Plastic “vapor barrier” had been installed both between drywall and insulation, and under the sheathing in about 1/3 of the house. So the fiberglass was a sandwhich surrounded by plastic. The top plastic was removed when the roof was done, and the lower plastic will be removed when the ceilings are done (soon, before winter).
Many years with NO vents in the bathrooms or kitchen. Bathrooms are well ventilated now, the kitchen soon will be.
Very poor drywall workmanship throughout, resulting in many air leaks.
When the roof (and sheathing) was off, I was able to accurately pinpoint the areas of damage. The worst by far was where it had the double vapor barrier, where there was widespread and significant rot. The 2nd worst was where there was active leaks in the roof. Last was above one of the bathrooms.
Any other location was actually doing fine. So I expect that correcting those problems will make a huge difference.
Ridge vents would be easy. Soffit vents are practically impossible. Part of the reason is that there are purlins every 24 inches between the trusses, which would block any vertical airflow unless there is some creative way that I haven’t thought of yet. Opening to the outside on the lower end would be a challenge as well, for reasons that are hard to explain here. But I will think on that more.
It is very unconventional construction, to say the least. I didn’t build it 🙂 But I am doing the best I can with it with my limited resources.
I have a steal on a big pile of polyiso, and with foil tape, great stuff, and caulking, I am confident I can get the system practically airtight. True, if it does get wet, drying will be practically impossible. I gotta think on that a little.
Thanks for your input.
Wow, sounds challenging. I’ve seen some ventilation systems for roofs that don’t depend on soffit vents but it might be impossible to retrofit the metal roof. Certainly your plan to carefully seal the polyiso should help. You can use multiple layers with each layer staggered from the other so the seams don’t line up making it very air tight. I’d still be concerned about the dead air space but you just have to do the best with what you got.
Thanks for the help. I am hoping to beat the odss, we’ll see.
Last question, I promise 🙂 – in areas with the lowered ceiling, is there any value in putting R19 batts there? So that there is a lower insulated area (for the living space) and an upper one (for the envelope) with 1-5 feet of airspace between? Would it help impede vapor travel if I use kraft faced? Will it reduce heat migration up to the higher airspace, thus keeping the living area warmer?
I realize that my questions are unconventional and require speculation, so your attempt to answer is even more appreciated. Thanks!
I’d be really hesitant to have dual insulation areas, especially in this configuration because this would invite condensation. Here’s why…
The fiberglass is completely moisture permeable, so any moisture that migrates up from the house will go right through the fiberglass. But, the fiberglass is a good insulator, so the sheetrock side of the fiberglass will be warm and the roof side will be cold. This means that the top insulation layer would be cold, probably cold enough for condensation to form.
With only one layer, the bottom surface of the insulation that faces the house will be warmer, discouraging condensation formation. That’s the way you want it.
Unintended consequences are the real enemy of energy efficiency.
Thank you!
Hi Ted,
I just bought a house that was built in 1959 with a cathedral ceilings that has ridge/soffit vents. The attic floor has some blow-in insulation but both my ductson and my water lines are up there and it gets up to 130 degrees up there. How can I properly insulate the attic? From reading your article, it sounds like closed cell spray foam is the best idea but that can get quite expensive.
Thank you for your input. It is greatly appreciated
In my own home of that vintage, I had a lot of cellulose blown in. That covered all the ducts, providing significantly better insulation for them and improving the efficiency of my system. Unfortunately, in the area of my home with cathedral ceilings and a flat section, access was very poor, so they weren’t able to do a complete job. It sounds like you have better access to your attic.
I would seriously consider doing an encapsulated attic – that’s what I would have done if I were to do it again. That is, I would treat the attic as part of the living space, putting the insulation under the roof as well as on the gable walls. Imagine that the attic is part of an A-frame home and the ceiling runs all the way up to the peak. You insulate between the rafters and under the rafters if possible. Then place the sheetrock directly under the insulation. Since it’s an attic, you skip the sheetrock and use a fire rated insulation board like foil faced poly-iso board.
In this way, you keep the air flow from soffit to ridge, but insulate just under that, leaving at least a 1-2″ air gap. The attic becomes much more comfortable extending the life and efficiency of your system.
Here’s a couple articles worth checking out
http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling
http://www.greenbuildingadvisor.com/cad/detail/interior-roof-insulation-retrofit-cathedral-ceiling-rigid-foam
Hi Ted – I’m looking to switch out my old A/C unit (3.5 ton) to an air source heat pump. I’m in New England and my primary heat source now is baseboard heat via oil boiler so I’m looking for the heat pump to provide supplemental heating. I plan to keep my baseboard heat, but my goal is to be more energy efficient and reduce my carbon footprint. That savings won’t hurt either of course. I’m leaning toward a two stage heat pump (4 ton). My question is, can 1 thermostat control the following: 1) two stage heat pump, 2) strip heat backup 3) baseboard heat? For a thermostat rated for 3 stages heat/2 stages cool, does the 2 stage heat pump count as 1 of the thermostat’s heat stages or 2?
As I understand the stats operation, the three stages would be: compressor low; compressor high; and backup strips/emergency heat.
I’ve often wanted to wire my own baseboards the way you’re talking but haven’t gotten around to trying it.
Here’s a handy description of thermostat wiring and how it’s used. You may be able to use the AUX heating, but that may be tied to the heat strips. You’d have to check the installation manual for the model of heat pump and thermostat you’re planning on using to see if there’s some usable combination. I’d personally try using the AUX line for the baseboard and detach the connection to the line that runs the heat strips in the unit since straight resistance heat is so expensive. The trick is that you’ll probably get a blast of cold air during defrost cycles.
Here’s a discussion of this type of issue
Ted,
This isn’t an energy question but you seem knowledgeable in all facets of construction so figured I’d ask you. I have a home built in 1887. It’s on a crawlspace foundation. Other than a few dips going from room to room (probably additions), the house is very straight and solid. I’m not sure how they laid the foundations back then, but at almost 130 years old I’m gonna assume the house is done settling. I’m looking to replace the aluminum siding and planned on using Hardiplank. I’ve done quite a bit of research, hee-hawed back and forth between different materials, but ultimately decided it was what I wanted. I stumbled across a blog yesterday that said the weight of fiber cement siding can be a concern for old houses, that it could cause additional settling depending on your foundation and soil type. This seems far-fetched to me; they said a typical home would have about 4 tons worth of Hardi, which sounds heavy, but between furniture, appliances, framing, and the weight of the foundation itself, I wouldn’t think the weight of the siding would make much difference. Your thoughts?
Standard disclaimer: I’m not a builder or structural engineer, so take anything I say with a grain of salt 🙂
FWIW, I used Hardiplank on my house as well after researching. It’s a great material and should last far longer than any of the plastic or wood alternatives.
I’m with you on this one. Spread that 4 tons around a foundation that is, let’s say for example, 200ft long. That’s a load of 20lbs per linear ft. Then, subtract off what the normal wood siding would weigh so the incremental load is even less. If your house is going to fall down because of that, well, it should probably be condemned and rebuilt.
I’m Planning to put a new roof on my newly acquired cabin. There is no insulation in the ceiling because there’s no attic it’s just open trusses with a 2×6 t&g ceiling. I’m Planning on using insulated panels on the outside before I install the new roofing. I’m concerned that this may cause the ceiling to rot in the future?do you have any advice on this type of insulation? Any advice would be great.
Thanks
That sounds like a good idea – insulated panels can work well when done right. The good thing about them is that their insulation helps keep the inside of the roof warmer, greatly reducing the risk of condensation damage. The trick is doing it right. Seams have to be well sealed, or the moisture in the air can get up there and condense inside the seam, leading to rot at that point.
Here’s some links to articles that might be useful:
How to Make a SIP roof better
Building Science – Over Roofing
Hi Ted,
Our split-level 1959 ranch in Atlanta has a downstairs room that’s partially below grade (with earth just below sills of 2 daylight windows on separate walls). Lately, the entire room but especially the back corner has been emitting a terrible smell that is sometimes rank (like a dead animal) and sometimes ammonia-like. The smell (especially the ammonia smell) is strongest inside a set of wood, built-in bookshelves along the 2 cubby holes at the bottom of the floor to ceiling shelves nearest that back corner. We pulled up the carpet facing the bookshelves and saw a browned stained area along the backing that indicates water infiltration, and the wood strips that the carpet is nailed to were rotten in a few spots. We took those rotten strips out and cut out the carpet pad there, but the smell persists at varying degrees of intensity. (It sometimes travels up the stairs at the center of the house.) There is no mold we can see on the carpet backing or on the old linoleum floor tile under the carpet pad. My questions are as follows –
1) Could mold or rotting wood we can’t see beneath or behind the bookcase be causing the smell? Perhaps water seeped through the cement block foundation or down the drainpipe into the foundation? The drainpipe is clear, but the gutters were partially blocked in the past.
2) Since the smell is rank…almost like food sewage or dead animal…is it possibly not mold, but sewage leaks? We have checked the sewer/plumbing drain pipes we can see and see no leakage from the pipes. There is a section of cast iron pipe somewhere under slab (plumbers told us years ago) that connects to downstairs toilet and then out of the front of the house to the street. Could a leak somehow have run down front face of house to that corner?
3) Dead animals often cause bad smells, but we can’t figure out how an animal would get into the wall or solid built-in-shelves between exterior brick and cement block foundation and solid, built-in bookshelves/wood wall paneling.
Any advice on source causes, how to safely investigate, or contractors to call without immediately shelling out $10K for nothing? My husband wants to crack open the base and back wall of the bookshelves and investigate. I’m worried about mold spores getting into rest of house. Two in our family (myself included) have terrible allergies.
Should we open the bookshelves first ourselves? Call a plumber? Call a mold inspector (not remediation) expert? Appreciate the help!
Sorry for the delay in getting back to you.
Same construction and age as my home which is built on a slope.
Usually, I’ve found that when something smells like a dead animal, it is a dead animal, but you may have a combination of problems. First, I’d look for a dead rodent. I’ve had them die inside walls and under cabinets – places that are hard to get to. Really unpleasant!
Given what you’ve discovered, it certainly seems like there’s a water problem also. I haven’t experienced an ammonia-like smell from water infiltration like that. Typically the smell is more of the familiar musty/moldy smell.
On question 2 – I’ve had similar problems with sewer gas due to improperly vented drain lines. It’s certainly possible that you’ve sprung a leak. I would think that the area would smell allowing you to trace the leak upwards to the source if it were running down. But if hidden behind other construction or buried, that would be a challenge.
3 – I’ve found mice can get through the smallest cracks. I recently found an entry point (mouse hole) on the outside of my block foundation. I think it’s burrowing down through the dirt and made it’s way through some bad mortar. Could be that you’re experiencing the same kind of thing.
Mold is ubiquitous, especially this time of year, but if you’re concerned about it due to sensitivities, I’d avoid that area. Typically, when a contractor goes in, they’ll put plastic sheeting all around do their work inside that little enclosure. It it’s near a window, you could even run a shop vac inside the area and have the air out from the vac go outside. This would suck air out of he enclosure, creating a zone of “negative pressure”. This is often what’s done in areas with hazardous materials to prevent dust/allergens/toxins from getting into the living environment.
With the proper precautions your husband could get in there to check things out. It all depends on how careful you think he would be in minimizing the risk of contaminants. It it were me, I’d do it myself, but that’s a personal opinion. You have to do what you feel most comfortable with. I wouldn’t want you getting ill, especially with your described “terrible allergies.”
I would want to know what type of problem exists before calling in a contractor. The’ll see the world through their own lens which can color what they see. A little investigation is probably warranted. If you have a good contractor whom you trust, you could have them do the work, explaining your allergy issue to them and see what they suggest about opening up the area around the bookshelves. Then you and your husband can decide which approach to take.
Ted,
Just wanted to let you know I spoke with Craig and his company doesn’t feel they are a fit for my situation. So back to the drawing board or mystery I go.
That’s too bad. If anybody could figure it out it would be him. But there are others in the area that you should be able to track down to help you. I think it’s really something that needs some Hands-On and eyes looking at the situation
i contacted someone else that wanted to charge 6-10 thousand dollars. That is way out of the budget. Really having a hard time finding anyone who can wrap their head around the whole picture.
Shari — what did they want that much money to do?
I explained the situation I am having and that was their quote. I didn’t go any further into the discussion with them as it was a crazy amount. I have searched the Internet for someone local and have come up with nothing. I am really getting frustrated with finding someone who can pin this down for me. The only people I can find are hvac companies and basic home inspectors for real estate transactions.
Hi Ted,
I have an unused masonry fireplace and I’d like to add a gas insert (direct vent, up the chimney). This is a 1941 construction in climate zone 6A. The fireplace is on the outside of the house. I’m asking bidding contractors to factor in adding a block off plate to stop air infiltration. My next problem is insulating that cold brick (not sure if it’s possible…). Is there any way to safely insulate the firebox (and in such a way as to not void a home insurance policy)? How about outside the firebox? Is it worth insulating the mantle face/sides (with 1″ XPS for example)?
I think I should pass on answering this. While this shouldn’t be difficult to deal with using rock wool, fire codes and requirements vary. Moreover, consequences of any kind can be lethal.
The best bet would be to talk to your local fire code officer and some good chimney contractors.
Sorry I can’t be more helpful.
No problem, I understand your reservations. The Roxul site says that its product should be up to the task, but since its product hasn’t actually been rated for this purpose, proceed with caution and at your own risk. I’ll see if I can track down a fire code officer in my area. Thanks for your time and quick response.
Ted,
We recently bought an 1809’s Victorian. Attic has 2-3″ of loose fill, air gaps gallore, and HVAC. Given the existing insulation and HVAC my thought is to insulate the roofline and bring the attic into the conditioned space.
Sounds good, but there are no ridge vents or gable vents. Currently ventilation is provided through two louvered windows. I would like to put fiberglass bats between the rafters and put 2″ foam board over that as a thermal barrier and air seal. I am concerned about having an unventilated roof.
We live in coastal virginia, humid, hot summers relatively mild winters. Any suggestions for this scenario?
Thanks,
Max
I’d be inclined to do the same thing. I’m less concerned about the roof ventilation as those old roofs are often fairly porous and, being in Virginia, you’re less likely to have super-cold winters where condensation inside the newly created ceiling would be as much of an issue as it would be, say in New York or points north. That’s assuming that you do a good job with the air sealing of the new ceiling so that warm, moist air from inside the house can’t get into that cavity.
For safety, I would make sure that the batts don’t touch the roof sheathing. Even without airflow, you want an air gap. Otherwise, the fiberglass can trap any condensation against the roof and rot it out. You might also want to look into the possibility of adding ridge vents and soffit vents so that there is ventilation through the cavity.
Another idea to consider is to skip the fiberglass and use foil faced poly-iso board foam, with the foil facing the roof (i.e. towards the inside of the cavity). The foil will help reflect the heavy radiant heat from the roof, which can be quite effective at reducing attic heating. Here’s some information on radiant barriers that might be helpful. I’ve experienced quite dramatic reductions in summertime attic heating with just radiant barriers, so when installed correctly, they can work very well.
Here’s a link to a company that sells the foil. (It’s just the first Google hit that looked good – I don’t endorse them.) Often, the dedicated radiant foil has a much shinier surface than the foil bonded to foam board, so it would be far more effective at heat reduction. You could staple that up first, then put up the foam board.
For moisture control reasons, I like to see two layers of foam, with the seams taped and staggered so they seams from the two layers don’t line up. That method makes for an air-tight barrier with good moisture control.
Thanks Ted,
I did a bit more investigating today. The rafters are 20-23 inches apart, rough cut 2x4s. Not going to be easy to put fiberglass in those areas. So maybe a few layers of foam board would be better? Thinking 1″ foil faced with a 2″ overlay. That should yield an R30, correct?
Additionally the roof looks like cedar shake with asphalt over top of it.
Foil faced Thermax foam board will give you a rated R-value of 6.5 per inch of thickness.
If you’re going to cut it to size and put it between the rafters as well as across the rafters, it’s best to install nailers to the sides of the rafters to provide a base for attaching the foam board and an air gap between the back of the foam board and the roof sheathing.
If you’re just talking about attaching the foam board over the rafters, then the nailers aren’t necessary, making installation much easier. With the old, uneven cut rafters, it would be something of a hassle to install the foam between the rafters. You would however be able to get additional R-value in there by adding, say, 2″ of foam in between the rafters, leaving a couple inch air gap to the roof. Then add full sheets of foam board across the rafters to insulate against thermal bridging. It all depends on how much effort you’re willing to apply.
In practice, it’s not necessary to go to extremes for R-value in situations like this. Even R-13 (2-layers of 1″ polyiso) will make a huge difference, since, by definition, R-13 means 1/13 the heat comes through. You’ll find that an air-tight foam board installation like this works much better than you’re used to with fiberglass of equal R-value, which isn’t air tight, doesn’t have a radiant barrier and doesn’t prevent thermal bridging through the rafters.
Hi Ted,
Her comes a long one!
I have a 1950’s cape and live on Long Island in NY. Our house has a small dormer on the front of smaller of the upstairs rooms and another small dormer on the back at the top of the stairs for a half bath. My issue is that the upstairs gets cold in the winter and hot in the summer. There are doors in the knee walls of the larger room that gives access to the crawl space from end to end on both the front and the back of the house. Unfortunately they are not insulated properly or at all in some parts. I have decided to use the Bonded Logic denim insulation bc I’m not comfortable with spray foam, the rigid board quote was expensive and the dense packed cellulose quote was the most expensive one of all. Rock wool was also suggested to me but I’m leaning towards the cotton. Do you have a preference in this situation?
When I install the batts I know to do the vertical walls and I figure to do the floors as well. But being that it’s crawl space do I insulate the peaked roof rafters? If so do I remove those pink attic rafter vents or go right over them? FYI the roof was replaced 6 years ago and has a ridge vent. Also there is a small attic space above the smaller room with a gable vent on the north side of the house. There are no over hanging eaves so therefore no soffit ventilation.
Also do I need a vapor barrier with the denim or rock wool? If so does it go down first underneath the insulation or on top of it? When all is done is it ok to put sheet rock up in the most accessible areas?
I appreciate any advice you can provide!
Thanks,
Michael
I like the Bonded Logic insulation and would use it myself for applications requiring batts as long as the joist spacing is a standard width. It can be a real pain to cut to a different width because it’s so tough (all those threads!) Other than that, it’s great to work with since it’s non-irritating. I also like the weight of it – it’s very dense and durable.
When you do the verticals, you’ll need to use the support wires to lock it in place. These are springy metal and install easily.
If I understand you correctly, you would not insulate the roof rafters in this space since you’ve already insulated the wall and floor which are adjacent to the living space. However, you do want to insulate the sloped part where the short walls meet the ceiling of the room. That should be insulated up to the flat section below the peak of the roof. And then across the flat section – every surface that is adjacent to heated living space.
Here’s an article with a diagram of this
Note – where they show the baffles, you definitely need to do this and you want insulation under the baffles (on top of the sloped section of ceiling). You have to have the baffles so that the insulation doesn’t come in contact with the roof sheathing because that has a tendency to lead to condensation, mold and roof rot.
As for the venting, note in the diagram from the article mentioned that they recommend gable vents when soffit vents aren’t available. I recommend that too. Without that, you can end up with conditions that lead to moisture issues.
Regarding vapor barrier – increasingly, in this type of installation, building scientists feel that they’re not necessary. you’re going to have way more vapor coming through those access doors than you would the sheetrock. But I do recommend checking with your local code enforcement office because they may require it and you don’t want to run afoul of their rules.
Your last question about putting up sheet rock. I’m afraid I don’t understand that one. Where are you talking about adding sheet rock?
Thanks Ted! That diagram is really helpful. I checked with my town and thankfully they do not require a vapor barrier. Can I assume that the specific location of the gable vents you suggest adding doesn’t really matter much? I might put one at a peak in the front of the house and the one for the other crawl space on the opposite end of the house. My reasoning is purely aesthetic.
I am however concerned about animals getting into the crawl space and eventually the house through the vents. This a valid concern? Any measures we can take to prevent that?
We use the crawl spaces for storage so I was thinking of putting up sheet rock or wood paneling or something in the most accessible areas just to keep that area clean. I figure the floor and the vertical walls that are they interior walls would be ok right? What about the roof rafters?
Thanks for your help! Michael
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Ideally, the gable vents should be in matched pairs on either end of each of the spaces in order to have the air flow through the entire space. Where not possible, one in each space will help. The air would then flow up through the vent chutes and out the ventilation in the peak. As you might imagine, the air will take the “path of least resistance” so some will flow up the first vent, then a little less up the next and so on.
As for animals, that’s a good concern! The gable vent manufacturers usually incorporate metal screening to keep out animals. But for best ventilation, the screening isn’t small enough to keep out bees and such.
You could certainly put of sheet rock or paneling after installing the insulation in the verticals and I’ve seen lots of people put flooring down over the insulation on the floor. Under the rafters? While I’ve seen it done with paneling, I’d personally leave it off since the underside of the roof sheathing will be the first indicator of moisture problems from inside or outside.
Cheers
Thank you for your help Ted!
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Thank you Ted, I will heed this advice.
I have a one story house with the air conditioner in the attic. The garage was converted to an apartment with its own air conditioner and heater, both also in the attic. I have a son who vapes and another son who likes to use various bath products. My mother is complaining that she is smelling tobacco (which no one smokes in house) and/or perfume (from bath products) is going into her room (which is next to bathroom) through the walls or through the vents. I have explained to her that no vaping is done in the house and any perfume smells go out the small side window in restroom or picked up through the fan in the bathroom. We’ve also tried air purifiers but she says they don’t work with the constant bombardment of perfume (her words). She is sensitive to environmental irritants. I am having a hard time figuring out how to deal with the irritants she says is coming into her room or into the house. She keeps her doors and windows closed in her room. I have told her that she needs to open the windows, at least once in a while to air out her room. She doesn’t. The garage apartment is on one end of the house while her room is at the other far end of the house.
So, ultimately, my question is can these irritants go through the walls or vents? And, is there a way to combat environmental irritants? She is the only one who is affected in my household. Thank you for any advice you can give me.
Hi Bonnie,
One thing I’ve learned is that it’s very difficult to argue with people with chemical sensitivities. The smoke or perfume she’s smelling could be residual odors on a piece of clothing. As you noted, if nobody is actually smoking in the house, then it’s not possible for her to be smelling something from you. However, suppose a smoker or heavy perfume wearer had visited her and sat on her couch. Those odors can linger for a really long time, especially if she doesn’t air out the house.
Your suggestion to ventilate her house to get fresh air is a great one. I installed a fresh air ventilator in my home and notice a huge difference between when it’s in use and when it’s not. With her sensitivities, it would make a lot of sense to have a fresh air system installed. Or, at the very least, periodically open windows to bring some fresh air in.
As for the question – odors could transfer through the ventilation system if they share ductwork. However, if the systems are independent, then it’s not possible.
On the other hand, depending on the home’s construction, air could be circulating from one side to the other through wall cavities, under floors, etc. These things can be hard to identify.
Some times, people will ventilate spaces under a slight pressure, which will force air out to other spaces and prevent odors from coming in. The simplest way to think of this is if you had a fan blowing air into her house. That would add air into the space and it would then have to find a way out. As it leaves, it would prevent air from entering from your house.
Something else to think about – every time she runs an exhaust fan, like a bathroom fan, a clothes dryer or a kitchen vent hood or has a fire in the fireplace, that sucks air into the house from wherever it can. If there’s any way for air to come from your side of the house to hers, it will get sucked in.
I strongly recommend that you look up “HRV” and “ERV” and see if you can have one of these ventilation systems installed in her house. They’re really worth the expense, especially under such circumstances.
Ted,
I’m about to tackle some insulation issues on my home and I stumbled across your blog while doing research. Your advice will be greatly appreciated. To give a little history, I have a two -story home built in the 1920’s in Atlanta that is very poorly insulated. It’s been remodeled for the most part, all new wiring and plumbing. No wires on the attic ceiling, no blue pipe, etc. It’s Victorian-styled with a crawlspace. Home is about 3500sf and has very tall ceilings. Less than R8 or so in the attic of blown in insulation. I can see floor joists. Crawl space had most of the insulation fall down because it was put in upside down (paper side down). I’m having a hard time. I plan on using the attic space in the future because I have about 1500sf of attic space with a 12′ roofline. Could potentially add another floor if I wanted. If i have to sacrifice this for energy efficiency, I will. I was concerned that just adding insulation would not help my main problem in the winter. So the main question is, tackle the attic or crawl space first to keep the house warm in the winter? Maybe a hybrid method if you know one.
The attic has soffit vents and ridgeline vents. I also have a working wood burning fireplace. There are no baffles currently installed so the insulation; which is hardly there has been blown away from the sides of the soffits. Crawlspace does not have mechanical vents and are always open. Found that this could be one issue during my research. Walking on the floor in winter can be a pain. My first project nearly broke the bank as I had to have a new HVAC system installed and new duct work installed and mastic -sealed properly. One unit is in the attic and the other in the crawlspace. Only way to do it in this old house. Walls are too thin.
Right now, I’m having to decide on which project to tackle first because of my budget. My home gets extremely cold in the winter time. Especially when the temperature drops below 30 here and it has for the last few years. The units run constantly and can barely keep the house above 20° above what’s outside in some rooms. When the temp dropped here in GA, the systems would not even reach 68°. Bottom floor has an open floor plan for the most part, so it freezes. HVAC system has been tested several times and little or no insulation was always the cause. System is found to be sealed properly. It’s not so bad in the summer time. I’m trying to find the most cost effective method to have a warmer house in the winter and save on energy costs. A little help in the summer would be okay too, but that’s not my major concern. My utility bill can range from $150 in the summer to about $900 in the winter and I still freeze.
I’ve had a few energy audits and I’m now performing most of what’s required. It was recommended that I air seal everything, add more insulation, seal the rim joists in the crawlspace, encapsulate the crawlspace, or spray foam everything. I’ve even considered rigid foam for the attic as a cheaper method to spray foam so that I could tackle the crawlspace. Adding more blown in insulation to the attic is also on my radar, not sure on it though. I’m just afraid that just adding baffles and more insulation in the attic will do nothing for my winter woe’s and would be a waste of money without a complete air seal which is just as costly down here as spray foam apparently.
My question is, and I’m theorizing this. Would it be better to spray foam the attic to stop the heat from being loss during the summer/winter or go after the crawlspace first? To stop the attic from basically sucking the cold air up through the crawlspace, walls, and ceilings? This is the theory that I’ve gotten from about 10 contractors who might just be trying to sell me part of a fix. Either will cost about $3k -$5K whether its crawl space encapsulation, close cell spray foam in the crawl space, or open cell in the attic. Been quoted for closed cell in the attic too. Regular insulation job with blown in is half the price of any of these. I’m trying to find the middle ground to what will give me the best cost/benefit or stop -gap until I can finish the other projects. I’m sorry about the very long post but I wanted you to have as much information as possible.
So the question is attic or crawlspace? Maybe a hybrid of both? Full seals are out of my budget right now. I’m 80% sure on open cell spray foam for the attic, but some blogs giving me doubt. I can only tackle one of the areas right now and will have to tackle the other next year.
Your help will be greatly appreciated.
That’s a lot of information which makes my job easier. I think you nailed it when you said the problem isn’t bad in the summer. To me, that say that even though the attic insulation isn’t great, it’s doing an OK job. The highly vented crawlspace has to be freezing your feet when it’s cold out.
I agree that the leaky attic is probably contributing to drawing cold air up through the house, so a complete solution would attack both. Understanding that you want to prioritize, I would personally go after the crawlspace – sealing the perimeter. In your area, just an inch of closed cell spray foam could profoundly improve the situation. I didn’t see what the floor of the crawlspace is made of. At the least, you’ll want to seal it with two layers of thick plastic, seams sealed. At best, you’d have an inch of foam sprayed on the floor too.
Be aware that the walls of this vintage house are often uninsulated or minimally so. The energy audits should have used a thermal camera to see what state the walls are in and if there are any other big energy holes.
Short answer – do the crawl space well. Then spray a thin layer of foam on the attic floor to seal it and add insulation on top.
BUT, if you are going to convert the attic space, spray the ceiling (under the roof) and completely seal/insulate that space at the outer most envelope of the inside of the house. Hope that makes sense.
Thank you Ted for replying.
I will take your advice and attempt to tackle both at once, but change my priorities a little for the crawl space. The crawl space basically sits on huge stone piers with beams. Some have been replaced with metal piers and concrete footings. I have a dirt floor covered with a thin plastic barrier. Insulation here is very low as they put the insulation in upside down when remodeling (paper side down) and most of it has come down; so i’m opting for a full replacement. This is surrounded by a concrete masonry wall with open vents. Walls are very thinly insulated. That is the project after next when I tackle windows and doors.
The project is going to take place a little later now since I had a roofing issue to tackle. Some monies had to be diverted 😦 for the roof. I have a kitchen section that does not have attic access and had a small leak. This part has it’s own roof line apart from the main house, but still sits over the crawlspace. When fixing the leak, it uncovered a whole lot of other issues; including no insulation in that area which I couldn’t get to unless I destroyed the kitchen ceiling or roof. That was determined previously by the thermal camera from the audit. I had to reslope and rebuild that entire area. While it was open, I insulated it. Try air sealing and crawling around with a hose on beams with about less than 3 ft of space at it’s highest point. It got interesting. I should finish this the same day the last contractor comes to look at the other project. I can say, there was an immediate difference in that area after blowing in insulation. Floor was still cold but the air temp inside was a lot warmer. No more cold air blowing through the flood lights. So that sort of tells me know that I really need to go after the crawl space air seal and vents like you suggested.
I have two more contractors coming out and I will make a decision which one to go with after that. I may have them foam the crawl space and air seal the attic and I will blow in the insulation since it was rather easy given the circumstances. I might give up on the space for now since I had to rebudget because of the roof leak. Thanks again for the advice. 1500 sq/ft is a lot of space to not use but might have to do what I have to for now. Winter is coming so can’t have Georgia Power “John Snowing” me this winter.
Victor – given the dirt floor of the crawlspace, that explains the insulation falling out. When I’ve seen that happen, it’s invariably because the paper facing has absorbed moisture coming up from the dirt floor. The facing then becomes a mold growth environment, so it gets eaten away. You’d be best off removing all that insulation between the floor joists, being careful to wear a high quality respirator or having a contractor do the job for you. Between fiberglass and mold, you’ll likely have a ton of airborne irritants during that job.
After removing that, doing the two layers of plastic sheeting, running a little up the walls so when you spray foam the walls, the foam seals the sheeting to the wall and keeps the moisture from sneaking out. Imagine that you’re building a boat – the entire plastic sheeting has to be sealed tightly. If you’ve done it right, you’ll probably have water building up under the sheeting, which is fine because that’s where it belongs – not evaporating and going up into your house.
With this type of solution, you’re making the crawlspace part of the conditioned house – much like a little basement. Often people will put a small heating supply register in there. That will keep air moving in the crawlspace and also keep it under a slight positive pressure. This constant flushing will also help maintain the space at a safe humidity level.
Good luck with your projects. Sounds like you’ve got your hands full!
I converted my 1958 brick veneer rancher from oil heat to a high efficiency gas heater and air conditioner last year. The ceiling was also air sealed and 11 inches of insulation was blown in. Since that time my cabinets have pulled away from the walls, window mouldings are gaping, foundation is experiencing cracking and I am getting some water intrusion in the corners of my basement. the humidity levels in the home are high when it is humid and damp out. No one can figure out what is happening with the home. the HVAc company recently installed a bathroom exhaust fan that exhausts continuously at 30 cfm and turns up to 110 cfm when it senses humidity. I am thinking about adding soffit and ridge vents to try to help with moisture removal from the house. will this help or hurt? and what do you think is causing this to happen.
Shari,
You may have multiple issues. I wouldn’t attempt a band-aid fix, like vents, without first determining why there’s moisture inside your house.
First question – was your oil heat a baseboard heating system (hot water heat) or was the heat distributed with air?
Second question – Are the air conditioning and gas heater part of one unit? That is, does your furnace have the air conditioning coils in it? I’m going to assume this is the case since that’s done 99% of the time.
Third and fourth question – What do you mean your cabinets have pulled away from the walls? How do you think this is related to the humidity issue in your house? I’m not saying it’s not possible, but I don’t really understand what’s happening and the relationship to the other problems.
Fifth question – How are the window mouldings gaping? Are you referring to the corners of the mouldings where there two pieces of wood meet?
On to some comments
I’m guessing that you went from baseboard heat to forced air distribution (question 1). In order to do this, they had to run ducts from the new furnace all around the house.
Typically, when people have dramatic changes in their home’s humidity after a change like this, it’s due to leaky duct-work and/or furnace housing. For example, basements are often fairly humid. And during humid weather, attics are too. Both are popular locations for furnaces/ACs. If the furnace or ductwork in is leaky, the system would suck that humid air in and distribute it around the house, causing the house to get humid very quickly. In dry weather, like in winter time, it would do the opposite, and cause it to be very dry in the house.
Symptoms of dry woodwork are that the joints open up because the wood shrinks as it dries. When it’s humid, wood expands. This expansion and contraction is normal throughout the year. However, extreme humidity swings are not normal under proper conditions.
If I were you, I would hire someone to come in and pressure test your duct system. I would have an independent company do this – NOT your HVAC company. You want someone who will give it to you straight. The same person should be able to find where large leaks are and prescribe how to fix them. The diagnosis should cost a few hundred dollars and is money well spent. You can spend thousands of dollars fixing random problems and still be no better off. I’ve been there – people would call me in after trying all sorts of crazy things.
If you search in your area for energy auditors or duct testing, you should be able to find someone. Again, I strongly recommend using an independent company or consultant, not a contractor that does this as a side business.
Thank you Ted for your input. The house was forced air oil heat so no new ducting was run in the house.
The window moldings are gaped at the corners when the ac was on in the summer. The hvac unit is located in the basement. I had a blower door test run on my house by an independent hvac company it came back as being borderline too tight. They recommended an energy star exhaust fan to run 30 cfm continuously and possibly an erv.
Prior to this project I had none of these issues. I have been told by a builder to install soffit and ridge vents and to get the insulation and air dealing out of my attic as it is holding in moisture. Mason feels that the blown in insulation has covered the air gap for the brick veneer and it is not venting now. Lastly I have looked for an independent expert in my area of Cumberland county, Nj and can find no one. Is there some kind of association I can call to get a recommendation? any other thoughts would be greatly appreciated. I don’t want to keep throwing money away
Thanks for the additional info. That’s interesting.
The gapping during the summer likely means that the AC is doing a great job keeping moisture down in the summer.
As for being “too tight” – that’s a good thing. You want a tight house, but as they noted, it would be good to add some ventilation. Personally, I’d go with an ERV as that provides controlled ventilation rather than just sucking air in from wherever it might come.
I question the builder’s advice. How is the insulation holding moisture in the house? Frankly, that’s crazy talk and indicates a lack of understanding of building science.
As for the brick veneer – I might have missed that. Did you have insulation blown in between the brick and walls where it could block the gap? That would be unfortunate.
Let’s return to the issues that have arisen.
Since the house is relatively tight now, it is less subject to the varying humidity levels outside. That’s a good thing. That means your living space will remain cooler and drier during the summer and warmer and more humid during the winter. Given what’s happening, the window mouldings must have been installed when it the wood had a higher moisture content. Now that the AC is working more effectively to reduce the summer humidity, the wood is shrinking.
The mystery to me is why it’s less humid during the summer than the winter. Usually, the humidity is very low in the winter. By any chance to you run humidifiers in the winter? I used to do that before I tightened my house because we’d get nose-bleeds. After I improved my home, I’ve never need to use a humidifier. Using humidifiers during the winter can be a really bad thing. When a home is humid in the winter, it is much more prone to moisture/mold problems.
If you don’t use a humidifier, then maybe the basement is damp? Can you think of any reason why there might be excess moisture getting into the house?
As for a reference, you might call my friend, Craig Arbaugh of Residential Energy Solutions. He’s up in Chester County, PA. Not close, but he’s extremely experienced and if he’s willing to come down, he could guide you really well. He’s extremely honest and, since he used to be in the building trades, he can look at problems from multiple perspectives.
The insulation was blown into the attic not the walls. There is very little insulation in the walls. The minute that humidity increases outside it rises in the house without the hvac unit running. Wondering if that is part of the problem.. No we do not use a humidifier in the house. The humidity level is always high. Summer /winter whenever the dew point is high. Had a structural engineer here he feels that by eliminating the use of the chimney with the power vented furnace and the sealing of the attic it the house is not expelling humidity and causing volumetric pressure on the house. But he has no suggestions as to how to fix it as he is not an hvac person. I will contact your friend. Thank for giving me his name.
Definitely contact Craig. It sounds like something that he should be able to figure out with a little bit of investigation and I don’t want you spinning your wheels with lots of people guessing at the problem myself included.
I should add that there’s definitely something contradictory going on here. If your house is as tight as the tests show, then the only way that the humidity could go up and down with the outside levels is if you have a severe duct leak. I’ve seen this exact behavior when someone has knocked a return duct off of its connection, so that it’s essentially sucking outdoor air into the system and distributing it around the house. But if that were the case, then the humidity should be high in the summer and your window moulding shouldn’t be shrinking, it should be expanding. So something is going on here that I can’t explain given the details provided. Hopefully will be able to help you and solve this mystery!
Thank you Ted for your suggestion. I just removed some of the cellulose insulation seay from my gable end wall and there is an airspace between the brick and the sheathing. Or I guess I should say was an airspace now it is filled on top with 11 inches of insulation. Not good. There are no disconnected ducts but I am sure there is some leakage . I sent an email to your friend. Awaiting a response. I will keep you posted as the mystery unravels.
Excellent! I hope we can get this sorted out for you.
Hi I have a question about my modular home which is basically a 1400 square foot Double Wide Trailer it came into sections it has vaulted ceilings which I have torn all the sheetrock off of what wasn’t destroyed in the fire I have rebuilt with vaulted ceilings again and planned on using tongue and groove barn wood for my feelings however after reading certain posts I don’t think that I should do that anymore but I am still faced with insulating above the sheetrock how should I do this the house is vented on all four sides through the soffits there are no ridge vent however there could be gable vents if needed but my more important question today is I have removed all the insulation from underneath the house which was soaked with water when they put the fire out it’s a crawl space that used to have a plastic tarp which held up fiberglass batt insulation I was planning on replacing it with closed-cell polyurethane type spray foam insulation on the bottom of the subfloor and coating the floor joist the plumbing and the new ductwork that I will install is this a good idea or a bad idea
The trick here is moisture control. Sitting above the ground without a slab, the moisture in the ground comes straight up and needs to be blocked. The original plastic sheeting served as a vapor retarder. Using spray foam would also work very well, probably better. My main concern would be if you need to do repairs or run new wires etc. – everything would be encapsulated in the foam, making this work quite difficult. OTOH, people often go decades without needing to do this type of repair, and closed cell foam would work really well, so as long as you think your ducting/wiring/plumbing that runs under the home is good for the long run, then you might want to go for it.
I would give everything under there a coat of foam to ward off moisture. So, rather than just going between the floor joists, give the joists a coating, even a relatively thin coating, of foam. You want a continuous moisture barrier protecting the wood and other building materials under there.
As for your ceiling, you can safely use T&G boards if you put something under them that is moisture impermeable. For example, you could use board foam, taped at the seams, then put the boards as your inner aesthetic ceiling. Doing this would reduce your worry about ventilation as well. You could have clear air channels through the ceiling from soffit to ridge if you added ridge vents. But if your original construction didn’t have problems with moisture with its construction, then if you replicate the original, you may be ok. Just be sure you avoid doing anything that allows moisture into that space between the ceiling and the roof.
Hi Ted,
I have an insulation question. Our house is a 1950s cape. We need to insulate the second floor crawl space. We have access to the whole length of the house (front and back) through the kneel walls in one of the rooms about 430 sq ft. I don’t want to do spray foam or rigid insulation boards. So I’ve narrowed down my options to dense packed cellulose done by a professional or Bonded Logic denim batts that I would do myself. The reason would be the batts would be time consuming but a significant cost saving. In your opinion is worth the upfront savings or is the dense packed cellulose a superior solution that will be better in the long run?
Thanks for any advice!
When I’ve done my own insulation projects, I love using the Bonded Logic insulation. It’s dense, comfortable to work with and neat. Just invest in the cutter because it’s hard to cut.
Hi Ted,
I’m confused over the “dry mode” of my basement mini-splits. The manual that came with my Gree units are worthless in explaining the most efficient settings. For example, in a basement that may tend to be a little damp, should I simply run the AC at a slightly lower-than-ambient temperature? Or should I put it in “dry mode” and let the fan run all the time–but at a higher temperature?
I have three 12,000 btu units in the largely-unused, 2,000 sq. ft. basement so “comfort” is not a big priority. But keeping it dry obviously is.
This article comes pretty close to demystifying “dry mode” it but not quite close enough. I think a dedicated article on “dry mode” is necessary. Thanks for all you do!
Thanks Jim.
I think part of the trick is that each company has their own definition. However, from what I’ve seen, dry mode simply runs the fan slowly and cycles the compressor so that it condenses water out of the air without over cooling the space.
The problem I’ve had with dry mode is that it doesn’t move enough air to be really effective. So I typically use air conditioning and set the fan as appropriate – usually medium.
If you want to do it more scientifically, you might just set a bucket to collect the condensate. Measure that for a day on one setting then try again at the other setting. Not perfect but gives a good idea of the effectiveness of each mode.
Ted,
I’m at the end of my crawlspace encapsulation project. I’ve run a 4″ duct to bring conditioned air into the crawlspace. Where should I terminate the duct? As soon as it enters the crawlspace, so it blows/fills the space, in the approximate middle, or all the way to the outside wall, like in you would place under a window? Or does it not really matter?
Thanks!
Andy
Since there’s no specific air return for the crawlspace, I wouldn’t worry too much about it. The only thought I have is to supply the conditioned air as far away from the coldest area of the crawlspace so the air has a chance to come to ambient temperature before coming in contact with that area to minimize any chances for condensation. But even that is probably unnecessary. This is the reverse of the standard that you mention for conditioned spaces where you’re trying to heat and cool the windows since you want a more even temperature distribution throughout the room.
If you can think of any other logical reason for placing it in a specific location, please share!
This is one of those situations where I should withhold comment. Anything around fireplaces/chimneys needs to be checked out by a local professionals. Sorry 🙂
I had previously emailed you regarding a problem I had with thermal expansion/contraction. We added a ridge vents to reduce the heat which did not work. The contractor talked to a GAF representative who suggested that the foam insulation board against the exterior wall, (which had signs of thermal expansion -bubbles in the vapor barrier) and suggest I cut holes into the board to allow air into the attic. That has worked in reducing the heat and also most of the banging noise. But I have two spots near my gas log fireplace that has plywood behind the flu that I suspect is expanding. Would you recommend that the wood be removed or holes be cut into the wood? The wood was used instead of foam insulation board.
Hi Ted,
We recently renovated an old 1940’s lakefront cottage. We raised one half of the roof and coverted it into a cathedral ceiling. Our “builder” acheived this by cutting into the existing roof line and extending a gable out. We have decided to go with dense pack cellulose due to the irregularities inside (our builder firred the ceiling and then put 2X4 over them which would have created a gap between fiberglass and the sheetrock). We have a ridge vent and soffitt vents and used the cathedral Accuvent baffles along the roof deck for the majority of the ceiling. My question is this: There are 2 large areas of ceiling that are part of the original roof (on both sides of the beginning of the gable), but that are part of the open cathedral concept. They are separated from the vented ceiling described above by large LVL’s and so they pose a separate insulation issue.These areas ultimately vent to the original ridge vent of the original house, into an attic space. But there are no soffits that serve these two areas. They originate at the LVL’s and they terminate into the attic. I would like to know what your reccomendation is regarding dense packing these areas. Since there is no air flow coming from a soffitt, should there be any air space between the cellulose and the roof sheathing? Or should it be dense packed in against the sheathing? Or should baffles be installed to create some type of air channel under the cellulose up to the attic. I’m worried about the cellulose sitting against the sheathing. I hope I’ve explained the situation adequately. I would love to attach pictures. Any ideas would be greatly appreaciated.
In general, vented or not, an airspace is safest since the roof deck will be the coldest surface and any moisture that’s in that insulation will tend to condense/freeze on it. If the moisture source is ongoing, it can cause real problems.
Having said that, I just had this very discussion with another energy consultant friend and our conclusion was that if it’s a tightly sealed cathedral ceiling, problems are rarely encountered. But when they do happen, they’re catastrophic.
The conditions which worry me:
Recessed lights are the most common culprit of rotten roofs that I’ve encountered. It’s well known that all conventional fixtures, even those labeled “air-tight”, let lots of air/moisture transfer from your living space into the ceiling cavity. The only fixtures I trust are sealed LED fixtures that are caulked to the ceiling. Just be forewarned – if you install conventional recessed lights, and whether you vent the cavity or not, there’s a very high likelihood that you’ll end up with condensation, mold and eventually roof rot.
Tongue and groove ceilings that are installed without underlying sheetrock are virtually impossible to make air tight and usually lead to roof moisture issues. Builders try to put plastic sheeting under it, and claim that it’s a moisture barrier. But as soon as they have one seam or one of the boards nailed to the rafters, what happens to that plastic? Holes! I’ve been the bearer of bad news on a number of occasions – “sorry, your roof is rotting and the only solution is to rip out your entire ceiling and sheetrock it like a normal cathedral ceiling OR sheetrock over that beautiful T&G ceiling.”
So to summarize – if your ceiling is well sealed and you’re confident there’s no place for moisture to move from your living space into the space above the ceiling, then there’s very low chance of problems (not impossible – nothing is impossible!), even without ventilation in the cavities.