Ask Ted!

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.


1,256 thoughts on “Ask Ted!

  1. Ted,
    The rear of my house is cantilevered 2 feet past my basement wall. My two possible options for treatment for these joist bays are as follows:
    Option 1. 2″ rigid foam on the top (underside of floor) and rim joist of bay, fill remainder with fiberglass, plywood on bottom of bays (exterior) rigid foam at foundation wall.
    Option 2. 2″ rigid foam at rim joist and on floor of joist bay, plywood on bottom of bays, bay left open to basement for conditioned air to circulate and for running of wires, ductwork, etc.
    Do you have any preferences or insights in regards to either of these two methods?
    Appreciation in advance!

    • This is exactly the construction of my house, but I’ve got a 4′ overhang. Option 1, by far, would be my choice. You want insulation right up against the floor, just like you’d want insulation right against the ceiling of your top floor of your house (i.e. on the attic floor). If there’s any air gap between the insulation and the floor, no matter how good the intentions of the insulation contractor, the cold air will get in there, rendering the space essentially uninsulated. This happened to me, and now I suffer with freezing floors in the living room all winter!

      • Ted,
        This must have been an error, I did not send another question and you did fully answer my question.
        Thanks again and have a great weekend!!

  2. Hi Ted. Im building a new construction home in bethesda Maryland. I finished insulation about 3 weeks ago. I did ALL of my interior walls and exterior walls above grade with cellulose. My attic level ceilings i did with Batt & the loft level was done with spray foam. Below grade i did batt on the exterior walls and cellulose on the interior walls and ceilings. I went to the property today to check on things and noticed that the interior cellulose looked damp/moist. Im guessing this was from the humidity. Im obviously very nervous about mold. Im happy to send you pics. Do you have any thoughts? thx!

    • During construction, while the house is exposed to the elements, the interior humidity will mostly track the outside weather. So if you get a warm, dry day, it should help to “suck out” much of the moisture that may be building up inside. However, this time of year is difficult, especially in your regions, with the hot-humid weather. This can really lead to high moisture conditions inside the house.
      Making it worse, when the house cools down at night, it can take a while to warm up in the morning. This can lead to conditions where the house becomes wet with condensation.
      Your best bet is to get the house sealed up as much as possible during construction so that the warm, moist air from the outdoors doesn’t easily flow in. This may not be possible, given the state of construction.
      Once the shell of the house is complete – exterior wall sheathing, doors, windows – it would be wise to get some industrial dehumidifiers working to eliminate the excess moisture in the building materials. You don’t want to close up walls and lock in the moisture. As you noted – that’s a recipe for mold.

  3. I have really dirty hardwood floors. They also may be urine soaked. I can afford to have them sanded. Suggestions?

    • I’m afraid I’m not a hardwood floor expert. However, I’d encourage you to look up an article on using white vinegar as a cleaner. I know many people who swear by it. It’s cheap and it cleans and disinfects well. It should also help with the urine smells.
      Good luck!

  4. Few questions. 2 yr old house. I put xps foam & drywall on unheated basement walls & xps, spray foam & drywall on rim joists. Dehumidifier is set to 45%. SHOULD I INSULATE BASENENT CEILING? Attic has ridge and soffit vents. Paid xtra for r39 fg insulation in floor. Now all fg is gray from top to bottom. WHAT DO I NEED TO DO? If I need a pro, what kind do I get? Thanks for helping a disabled Veteran and old lady!

    • If you insulate the walls, you usually don’t want to insulate the ceiling of the basement because you are trying to make it part of the heated house. Letting some of the warmth from the house get into the insulated basement is a good thing as that will help reduce moisture buildup (and mold) in the basement.
      Usually gray insulation in an attic is and indication of air moving through it. The gray is usually just dust trapped by the fiberglass – it acts like a big air filter.

      When you say “all fg is gray from top to bottom” are you being literal? I mean is all the insulation really completely gray? That would be extremely unusual. Normally, there will be gray at some places, where it can trap dust, but other places, it will be fine. Especially on a new house. It usually takes years/decades for the fiberglass to get really gray.

      If there’s extensive graying of the fiberglass, this may be indicating a bigger problem. If you can post a photo somewhere, that would help. You can post to my Facebook page:
      and I’ll see it there.

  5. Wow, I have read several of your roofing insulation articles and am some what confused.
    I have two problems : (1) Bedrooms with flat ceilings . (2) Cathedral ceilings in the living area. Both sections have tongue and grove pine stained boards. There are ridge vents at the peaks and soffits around the perimeter of the house into the roof. In the attic above the bedrooms I can see that the fiberglass is collapsing and the openings into the cathedral space is packed with fiber glass making that section separate from the bedroom section. The cathedral roof floor has 1″ rigid foam and R19 fiberglass.

    My first goal is to insulate the bedroom section and then tackle the cathedral section, which is difficult and tight to get to from the attic.

    1. I am thinking of removing the fiberglass in the bedrooms and using closed cell foam. Here are two options as I see it:
    (a) Insulate the roof and seal off the ridge vents and soffits
    (b) Insulate the floor of the attic. (Yes I have ductwork and bathroom fans and electrical wiring all over that attic floor)
    If I do (a), then I would still have moisture escaping into the attic, with no other place to vent out to.

    I look forward to your advice.

    • Given your situation, that sounds like a good configuration for creating an insulated attic. Pull the fiberglass and seal the attic just like it was a room with a cathedral ceiling.
      You’re right that the moisture will get up there, but with the attic insulated, then it’s little different from the rest of the house. However, it is typically recommended to put a small air supply and return in the attic (as far apart as you can for good circulation) in order to keep the air flushed, filtered and moving. You don’t need a huge amount – often people will just use a 4″ duct, like a bath fan size, to supply air to the attic.

      Just make sure the foam company has a good track record. I’ve seen situations with less experienced foam companies that don’t get their foam temperatures or mixtures just right and it doesn’t cure properly leading to horrendous outgassing and ongoing odor problems. Definitely, check references – it’s a big investment and you want it done “by the book.”

      • More questions from your response:
        “You’re right that the moisture will get up there, but with the attic insulated, then it’s little different from the rest of the house. ”

        Different? What to do about the moisture..removing the floor insulation will give faster access to more moisture that seems to me will have no other place to go but reside in the attic? As it stands now, the ridge vents and soffits allow for some air movement. When all is sealed as you suggest, the moisture will then be remain there.. Is there something I can do to remediate that? Something to absorb the moisture, something to detect and extract to daylight? I would hate to have a mold problem.

        “put a small air supply and return in the attic ”

        Will this supply bring in fresh air? From where will the supply come from? The lower part of the house, below the attic? What is the right location for this fan? Up at the top or on the floor. Its about 1000sqft up there, is one small enough ? Running 24/7?

        One thing I forgot to mention is that I also have a roof fan to the outside on the roof that turns on when the temps are over 90F. I imagine that I will have to remove this and patch up the hole on the roof.

        I look forward to any suggestions

      • Moisture itself isn’t a problem – it’s the level of moisture that causes issues. By sealing the attic at the exterior walls/ceiling, you’re making the conditions in the attic the similar to the interior of the house. If the moisture in the house is normal, the same moisture level in the attic won’t be an issue.
        Using a little of the air from your central air to circulate into the attic helps to dry out the moisture (in both the house and attic). You can just tap into the main ducts for supply and return air. You do not want fresh air, as that is often more humid than normal house air. Ventilated attics with soffit and ridge vents actually just track the outdoor humidity, swinging from very dry to very humid, often over a single day.
        you would remove the roof fan if you insulate the space. While it will get hot up there, if you insulate it well, it should be considerably more comfortable than it is now.

  6. Ted,
    What are your insights into insulating a garage? Right now my garage is bare studs, no drywall anywhere, ceiling or walls. I have plans to cover the ceiling and walls, I haven’t decided on drywall or plywood for the walls. I am thinking about insulating the walls, just to keep it cooler in the summer and possibly warmer in the winter, with the help of a small space heater or salamander. What are your thoughts about insulation with a vapor barrier for the walls, do I need a vapor barrier? It’s not actually living space and won’t be conditioned as such. Also, with it being outside, there won’t be any of the devices that produce extra humidity, like within a house, just whatever is naturally in the air.

    • Hey Andy,
      I had my garage insulated. They just used standard faced fiberglass, though the facing is optional since there shouldn’t be any moisture sources in the garage and, typically, the garage air exchange rate is such that the moisture levels will track the outdoors pretty much. So your thoughts on this match my experiences.
      I also use a radiant barrier on the rafters in the garage attic and it made a huge difference in the summer.

      • Thanks Ted!
        My garage roof is trusses as opposed to rafters. So I’m assuming you would recommend some sort of foil faced polyiso on the bottom of the truss chords? And then fill in the bays above the polyiso with fiberglass batts?

  7. Hello Ted,

    First , thanks so much for all this info. Quick question. I bought our first home (ranch style), which has a regular attic in 2/3 of the house, but a cathedral roof in the large master bedroom. The snow above the cathedral roof just melts every time we get snow (Hudson Valley NY) and the air up near the ceiling gets really hot in the summer (so I know I have poor insulation). The sofits are vented, and I found that the builder installed baffles and R-19 fiber glass mat insulation in each rafter section. The ridge is not vented. If I add a ridge vent, can I blow in cellulose insulation up through the sofits using a long pvc pipe? I figure that the baffles should keep the roof vented and cold enough to prevent moisture problems right? Any suggestions would be greatly appreciated. BTW, I’m an electrical engineer, so if you or anyone else has any electrical or home automation questions, I’d be glad to help. Thanks.


    • It depends on the construction of the cathedral ceiling. Many people have successfully used dense-packed cellulose without venting and had no moisture problems. If the internal cathedral ceiling is solid plaster or sheetrock (i.e. no recessed lights or other “holes” that allow moisture to get into the cavities) then there’s little risk. OTOH, if the ceiling is filled with holes, then all the venting in the world doesn’t help.
      If the R-19 was done properly, you shouldn’t have that much snow melting. Even though the insulation could be higher, a true R-19 would keep the heat in well enough. My guess is that they did a lousy job. You could have someone come out with an infrared camera to look at the ceiling during the heat of the day to see what it looks like. That would let you know what’s really going on.
      Doing dense-packed cellulose yourself would be tough. Even many of the professional cellulose installers don’t do it right. You’d really be best off finding an installer in your area, if any exist, who has done dense packed cellulose in this type of situation.
      If all else fails, you could build-in the ceiling a couple inches. Adding 2″ of polyiso board foam to the inside of your existing ceiling, then sheetrocking over that. That provides a “thermal break” giving insulation under the rafters and everywhere else. 2″ of polyiso adds R-12 to R-14 and pretty much eliminates any possibility of moisture getting up into the roof cavity.

  8. Hi Ted,

    I have a 16 year old pre-manufactured home. I’ve been in this house almost 2 years.
    There is no basement, just dirt under the home, the belly on the underside, and breathable skirting all the way around the house.
    Last year my furnace worked fine (original furnace to the home), but this year something happened. One day, while I was at work, the house seemed to get very cold. The furnace was working fine up to this point. The house was getting colder as it got colder outside, but about 10 degrees colder than what the thermostat was set at, and even colder from there. The furnace would run, gas lights, everything appears to work, but air is seeping out of vents more so than blowing and the sounds of when the blower kicks on is different than before.
    I tried replacing the thermostat, no luck there. The next day I called a heating and air company (from a sticker with their information on the front of the furnace). They came, inspected everything, saw the light blinking was showing ‘Limit Switch Open’. They replaced the lower limit and left, telling me to turn the furnace up to my intended temperature and let it run.
    I let it run, went back to work, and came home to a colder house. They said it was over heating, and shutting itself down. They said the limit switch they put on was a bit bigger and would give it a little more time to run before shutting down. The next day I called and stated I was having the same issue and they told me it would have to be something underneath the house, in the duct work. But, they didn’t deal with that and didn’t have any information on someone who could, but said it would need to be scoped.
    After this, I did replace the upper limit switch to see if that was the issue, as they weren’t going to come back and make sure it was fixed.
    NO such luck.
    I then called another technician. Came right away and seemed much more thorough on the furnace, it’s process, how it works, etc. He checked multiple things, looked at the schematic, checked the coils, air coming out of vents, etc.
    He noticed that it was pulling the same code, based on the blinking light, that the limit switch was open. He had talked to someone else on the phone who was a bit more aware of these type of homes furnace issues. He said it sounded like there is a hole in the heat exchanger, causing the air to cool down before it can be blown out into the house, etc. He also said there could be some rust inside the metal piping to the outside. None of this was torn apart, just a basis on what they already knew/tested?
    I put in a claim with my insurance agent, and she forwarded it to the company who took care of it. IMC was the overseer, and Heartford Steam Boiler was the company making the decision. Heartford talked to me, and the technician. Heartford said they are not covering the furnace, for replacement or repair, because of ‘rust’ showing that the furnace is old. After this my agent called, and they told her it was because the unit was still running. That wasn’t in what they told me or the letter to me.
    I feel like something is a bit fishy, so I guess I’m not taking no for an answer before I purchase a new furnace, not covered under insurance.
    Could this be in the duct work under the house? I know that would consist of cutting the belly open, but the air coming out of the vents is faint, not strong like before, and my house is very dusty (I usually clean all the time and dust has never collected like this). I also took the front off the furnace (which holds the filters) and they didn’t look a bit dirty. The technician did say the air coming up through the vents was plenty warm, it’s just not blowing.
    I have pictures of the furnace and the under belly of the house. There is one spot under the dining room where the belly ‘sags’. There is not water dripping from it, but it’s lower than any other part of the belly of the house. Should I have this cut open to check the duct work? Should I find someone with a scope? Just looking for a 3rd opinion before I purchase a new furnace.
    Thank you!

    • Thanks for the detailed description, you’ve been working hard to get this fixed – it has to be frustrating: you would really think these guys could figure it out!
      So, to recap, the high-limit switch keeps getting thrown because there’s insufficient air-flow and the system overheats. The limit switches are doing their job and preventing your house from burning down. I’m kind of surprised that the guys tried replacing the switch rather than just measuring the air flow – it would have been obvious to any qualified technician that this is what happened.
      Since the system had been working fine and now doesn’t, we have to look at what changed. Did anything change about your house or your system? Think hard. People always say “no, everything’s just the same” but it almost always turns out something changed. Like I’ll find out – “oh, btw, we remodeled the entire house and changed the ductwork” 🙂 So think hard. Did anything change between the time it worked and it didn’t?
      The clean air filter is a big clue. If there was a hole in the return air ductwork or something like that, the filter would be really dirty. Again, it points to there being inadequate air flowing through the system.
      Is it possible that the blower is dying? If the fan’s bearings are going, and the blower is turning slower, then much less air would flow through. Try to remember what the system used to sound like and compare it to now.
      Another thing to try is to switch off the heat and turn the fan to ‘on’ so the blower runs without the heat (to avoid overheating). Next, take off the access panel for the filter. Hopefully, you can run the system with that off. There should be a strong suction on that panel when the fan is running and you should feel significant air flow into the system when you open the panel.
      Assuming you can run the system with the panel off, see how much air is coming out the air vents around the house. Compare this to with the panel on. If the return air ducts are ok, the air coming out the vents should be just as much with the panel on or off. But if something is blocking the return air duct, then the air flow will be way different with the panel on or off.
      If the air flow is poor in either case, there’s still one more thing to check – but I’m not sure if you’ll be able to do it. If the air conditioner coils inside the blower are really dirty, that will greatly restrict the air flow. This is fairly common. Did the techs try cleaning the AC coils or inspect them to ensure they’re clean?
      Does your house have a single central air return? If so, is there any chance that something is restricting the air getting into the system?

      Finally, if they suspected that the heat exchanger has a hole in it, they should have immediately tested the system for carbon monoxide. Heat exchangers with holes allow the air from the combustion to mix with the air from the house. This can kill you! No exaggeration. If they seriously thought that, they should have immediately disabled the system so that you wouldn’t poison yourself, and replaced the heat exchanger.

      Hopefully, this will give you some food for thought. If it is your heat exchanger, absolutely get it fixed ASAP.

      • Hi Ted, thank you so much for your thorough information and suggestions of things to try.
        I did take the filter panels off, they are clean, and the air coming out of the vents is the same, just seeping out.
        I JUST turned my air on, and same thing is happening, air seeping out, but metal on vents are very cold.
        I didn’t do anything or make any changes, and you suggested to think about. The furnace got louder, or so I thought, with it running. It feels like air is blowing out of the fan on top of the furnace system.
        The one thing I noticed when the furnace stopped working correctly is how the blower sounded, it sounded different, and when it was working correctly I could hear the flu flap open and shut, and it didn’t after that. I haven’t had anything done since I’ve tried your requests, and have waited until now to turn it on to see if it’s any different with the air on.
        Thank you again. Sorry for my late reply. Promise I will reply sooner, I appreciate the help!

      • It definitely sounds like you need a service call to have it looked at by a pro. Low air flow can be caused by several issues and a tech should be able to figure that out quickly.

  9. Ted,
    I feel like I’m venturing down the rabbit hole here, and it may not matter either way, but unfortunately that’s not the way my mind works most of the time.
    I’ll try my best to verbally draw a picture of my situation. As you know, I’m bringing conditioned air into my crawlspace: 14’x14′, 2×10 floor joists, 24″ to the bottom of the subfloor, attaches to the basement on the south end, three other sides are exterior walls. Vent for the room is on the far north end and the floor joists run east to west. I’m bringing conditioned air into the space via a 4″ flex duct in the south east corner. I know I should take that duct to the furthest point in the space, but I’m not really sure what that is in this setup, with a square. Logically maybe the center of the north wall, blowing back towards the basement/south wall? But that is more duct and turns, reducing air flow, etc. Do you think I could get away with terminating it in the middle of the east wall, with the vent blowing east to west? Since that’s the way the floor joists run I thought it might help with the conditioned air getting up into the floor joist bays and to the underside of the floor, but I’m not as well versed in air dynamics as you are.

    • great question Andy. Honestly I can’t give you a great answer. my feeling is that moisture diffuses in the air, and not natural diffusion will help distribute it throughout the space. likewise, the drier air that you’re bringing in should help to remove that moisture as the moisture will move from areas of high concentration to low concentration. as such, flooding the space with good air should help as long as the moisture isn’t too extreme. I’m just kind of logicing my way through this, but can’t say definitely.

      • I’m hoping there won’t be a large amount of moisture. I’ve been very diligent in properly laying down and sealing a vapor barrier and then encapsulating the entire space in 2″ rigid foam and sealing all joints. I’m really only adding the conditioned air to help temper the space and exchange air to hopefully keep it from getting stagnant.

  10. We have a dust that is accumulating daily. When I gather it together into a baggie, it almost looks like dryer lint. Our dryer vents directly outside. We had the popcorn ceilings scraped and retextured but it was all done through an abatement company since there was asbestos and they used filters and put plastic up. We don’t think it is that. We have new carpet in three bedrooms and the rest of the 1700 square foot ranch home has hardwood. The basement is unfinished, the hvac is in the basement. The ductwork is old and is insulated on the inside. The insulation appears to still be intact. We have had our ducts cleaned twice. We cannot figure out what is causing this horrible dust problem. We had an electrostatic filter installed on the furnace and a mold light. We had some canned lights installed but the electrician assures us they are sealed. Please advice. We are in the Kansas City area and do not who to contact.

    • that sounds like the ductwork is leaky and sucking in insulation from the attic. Do you know if the ducts run through the attic? What time type of insulation do you have up there?
      there are duct tests that can help find the problem. I’ll post some links as a follow-up.

      • Hi Ted, we had our ducts sealed with aeroseal, the attic foamed over all penetrations and new blown in fiberglass, then the basement rim was sealed. We are still getting this dust all over. Our furnace filters never seem to get dirty. Our next step is to install a hepa filtration bypass system on our unit. Any other ideas? Should we bring in air scrubbers? It is awful trying to clean it. It just smears when you wipe it with anything damp, when you try to vacuum it, it smears with the vacuum brush. Thank You

      • If your filters are never getting dirty, then the system isn’t circulating air well. Have you tried testing the air flow? You can hold a newspaper sheet up to the air intake vent. It should suck very strongly onto the vent.

        Another thing – you say it smears? That shouldn’t happen with dry fibers, like insulation or dryer lint. Are you sure it’s a fiber? Have you looked at it with a magnifying glass or had it analyzed? If it smears, that sounds like some sort of grease. Maybe mixed with dust. For example, if your fry food, it creates an incredibly tiny mist of grease particles that get everywhere and is hard to clean.

        It sounds like you’re at the point where you need to get the debris analyzed by someone experienced in “indoor air quality.” You’ve put enough money into remediation work and it hasn’t helped (though it will benefit you in the long run by tightening up your ducts and insulation). But the dust/debris problem needs to be solved and from what you’ve said, it’s not related to the HVAC.

  11. Hi Ted,

    I am hoping you might be able to solve an ongoing problem. We recently encapsulated the crawl space of our home ( closed cell foam on walls, 12 mil vapor barrier on floor and dedicated dehumidifier). Radon piping ( 4″ corrugated pipe) was added beneath the vapor barrier as a precaution during encapsulation. Unfortunately we had to add a radon mitigation system after the crawl was encapsulated, even though we were well below EPA guidelines before encapsulation. A sufficiently sized radon fan was added to the existing system-the fan is located outside, and terminates with a 4″ pvc pipe just above the roof line.

    The problem we are having now is we have been experiencing increased humidity during the humid summer months ( we live in humid Tennessee) ever since the radon system was installed. We had a blower door done, comparing the cfm with the radon fan off, and on ( HVAC off). The blower door results revealed the radon fan was placing a 250 cfm negative pressure on the home.

    Is a negative pressure on a home a problem, and could it contribute to humidity issues ( dry in winter, humid in summer)???


    • As I read your post I was wondering if it could be a negative pressure issue. Glad you actually had it measured! That’s exactly the issue. That 250 CFM has to come from somewhere. So it’s sucking the air out of the house and it gets replaced by humid outside air. Before you know it, the indoors would be as humid as outdoor!
      if the radon level is low, why do you have to run the system? Seems like a waste.
      if you have to run it, then you could provide a little fresh air inlet directly into the crawl space. that’s better than sucking the air into and through the house.

      • Thank you Ted.

        Unfortunately, we need the Radon system to work-radon was at 10.2 pCi/L just after encapsulation. The fresh air inlet sounds good, however we have had the crawl space sealed up extremely tight ( closed foam cell, 12 mil vapor barrier with clear termite strip) and also have a ducted dehumidifier down there ( Ultra Aire). I’m concerned adding fresh air would defeat purpose of trying to keep humidity down ( below 50 RH), especially since we are in humid TN near a river (fog-high dew points). We also have four ( yes four) Mitsubishi Citi Multi air handlers underneath the crawl space-which were sweating with condensation ( especially on refrigerant lines) before we had the crawl space encapsulated. Sad thing is, once we fixed the crawl humidity by encapsulating, we created another issue-Radon. Radon was checked beforehand and was well below at 1.2 pCi/L. After the radon system was installed, we noticed an immediate increase in indoor humidity ( 10% increase).

        Any thoughts or recommendations are appreciated-thank you for your time.


      • Ok, so it sounds like the crawl space must have been well ventilated before, so it was flushing out the radon. When you sealed it up, the radon had a chance to accumulate.
        I’m still confused as to why the radon system is sucking so much air from the house itself. There should be a little but it sounds like the full force of the radon system is sucking air from the main part of the house.
        You’re right, adding some ventilation will defeat the purpose in the crawl space. However, the radon system has merely shifted that humidity to the entire living space. So now your air conditioner has to work overtime to both cool and dehumidify the outdoor air that has been sucked in by the radon system.
        I really can’t think of any solution as it stands because of the way the Radon system is sucking air into the house. That “make-up” air has to come from somewhere. Either through a direct vent into the crawl space or via random leakage into the house. In the first case, you get humidity in the crawlspace that you were trying to eliminate. In the second, the entire house humidity goes up. The only thing you can then do is use more dehumidification, which the air conditioners is very good at. During the winter, you’d have to humidify to get to a comfortable level.

    • BTW – are you sure it was a true 250CFM as opposed to 250 CFM@50? The latter is a term that gives how much flow there is at a certain pressure whereas the former is a true measure of air flow.
      Most Radon fans move less than 200CFM and that’s supposed to be air drawn from under the slab. If it’s just drawing all the air from inside your home, something strange is going on.

      • Not sure… the blower door test ( done on interior 1st floor/HVAC) off results were:
        2554 cfm- radon fan on
        2796 cfm-radon fan off

        I believe the results were done @cfm50, just not sure. I know he mentioned something about the house being well sealed since it was around 3 ACH. I never got a written report, or detail…just a quick verbal-so I don’t understand. I do know there was a 250 cfm differential with the fan on vs off. We specifically requested the bower door test to measure the affect the radon fan had on the house pressure.

        Hope this helps.

        Thanks again for your time and input!


  12. Ted I have an older 1900 built 2 story house, upper story is 75 percent finished plaster but a rear section is accessable by two doors from two finished bedroom next to one another. This area has tongue and groove wood up the short (1 foot) side walls, up the slanted walls to the ceiling (which has been more recently covered with something else), and the gable wall in the rear (which has an old door to no where and a small window in it). The tonge and groove seems to have some type of tape on ALL the seams There is blown in insulation above the bedrooms and probably this space also. The tongue and groove has peeling paint (latex over oil paint perhaps or perhaps temperature changes here in mid Michigan). I doubt there is insulation in the walls of the home. I would like to convert this space to a walk in closet for the two bedrooms, as there is normal height head room. I could add knee walls, remove the tongue and groove or just go over the tongue and groove without a new knee wall. There doesn’t curretly appear to be any moisture issues in the attic spaces, there are gable and ridge vents, so I am trying to leave the sleeping dog lay for the most part. Can I place ridgid foam over the tongue and groove, then drywall over it without causing any issues? Do I even need the ridgid foam? If I take the tongue and groove down- I think I would need to place baffles to the attic(ceiling) level, then batting, then rigid foam before drywalling would that be correct. Just me and a tight budget trying to get this project off the ground any advise will be much appreciated!

    • If it were mine, I’d just go right over the T&G the way you said. Maybe an inch of rigid foam board then drywall. This will stop any moisture from getting up there and greatly reduce the chance of moisture issues. They probably taped the seams due to moisture problems at one point.

  13. Ted,
    I have question about insulation on a cabin I am building in North East Texas. The cabin is 16’ by 24’ with a loft over half of the cabin, above the loft is a cathedral ceiling. The house is pier and beam with 24’’ crawl space, the outside is OSB wrapped in Tyvek and covered with Smart lap siding, the wall covering inside will be tongue and groove pine boards and the ceiling will be open rafters with bead board in between the rafter with a 1.5’’ gap between roof decking and bead board (caused by furring strips for nailers). This cabin will be powered by solar and will not have a/c running while we are away, we will use a window a/c in the summer and a wood stove in the winter. My biggest concern is creating a place for mold, so my question for you is, would it be ok to not have any insulation in the walls or ceiling? Will the airgap between the roof deck and bead board with no insulation cause problems? There is currently no roof ventilation but I will be installing a solar fan in the wall in the loft to act as an air exchange while the cabin is not in use.

    Thank you,

    • Since you won’t be occupying or heating/cooling the cabin while your away, you want to be sure that it naturally takes care of itself. This can be challenging in certain climates, especially if it’s a naturally wet climate. Northeast Texas can be very humid, so you’ll need to be really careful or you could end up with a moldy mess.

      Mold growth depends on having a sustained, elevated humidity, so it really depends on what the conditions are where you’re building the cabin.
      Since you mention not insulating, that implies a modest climate. However, even if you don’t have significant temperature swings, you could benefit from insulation, even a small amount could help by reducing drafts and air movement through the house. This helps keep the moisture levels in the house more steady too. If you have a very ‘open’ house – one where air flows in and out easily, then the humidity level inside the house will follow the outdoor humidity closely. This can be dangerous at night because that humidity will still be in the house as the nightime temperatures drop. When the walls or roof cool off at night, if the moisture that’s still in the house comes in contact with these cooler surface, you get condensation, much like what you get on windows when you take a shower. This is where a bit of insulation and air tightness can help.

      For example, just using 1.5″ poly-iso foam board between the nailers in your ceiling and walls would help to greatly reduce your air conditioning usage during the summer. It would also minimize the amount of cooling of your roof deck by the air conditioning, which, if allowed to happen, could cause moisture buildup.

      With your crawl space, if the ground beneath and around the house is wet, a lot of water vapor could enter the house if the crawl space isn’t sealed tightly. You’d want to ensure that you block that moisture. If the crawl space is to be paved, they’d want to prepare a moisture impermeable barrier under the slab and around the foundation walls. If it won’t be paved, then a double layer of heavy plastic sheeting covering the dirt floor would be important.

      I would also recommend talking with others in your area who have done similar buildings. They could tell you what worked for them and what didn’t. You’ll probably get conflicting info, but if you talk with a variety of people, especially building professionals, you’ll probably be able to get a good idea of the do’s and don’ts of building in that area.

      • Ted,

        Thank you so much for the response. Sorry for my delay, I have been away and could not respond. with the poly-iso foam board should the foil side go facing in or out.

        Thank you so much

      • I think it’s actually encapsulated both sides with foil but sometimes they have a shiny side vs one covered with something. For best effectiveness, the shiny side should face an air space as opposed to being pressed against wood or another surface.

  14. Ted,
    I’m sure you’ve covered this somewhere in your masses of information, but I can’t seem to track it down. What is your opinion on flex vs. rigid duct? I personally would prefer rigid, but I’ve run into a situation in a crawlspace where the duct run to the register boot is not a straight shot (it’s on an angle), and there’s a change in height, so I’m looking at a couple elbows to make the drop. Flex would make this new run tremendously easier, but it’s also the farthest register from the furnace, so I want to make sure I have good air flow. I feel like I’ve seen studies where there’s not much difference between flex and rigid if the flex is installed properly and pulled taught, but I also know you can never clean flex if you needed to. Any thoughts?

    Much thanks!

    • I prefer rigid wherever possible but sometimes flex is just so much more convenient and easy to work with that it makes it worthwhile.
      IMHO, the main thing is designing the duct system “by the numbers” regardless of the type of duct. Keep it tight, support it properly to avoid undue bending (which increases the air resistance) and use the appropriately sized duct for the flow.
      The nice thing about it is that it comes insulated and you only have connections (and potential for leakage) at the ends.

      • Exactly my thoughts with the flex! It would be so much easier in this 18” crawlspace, and it’s only two connection points, and like you said, pre-insulated. Otherwise I’m looking at 3 sections of rigid, screwing & taping their seams, sliding insulation sleeves over them, etc. Maybe I’ll try flex for this room. Worst case scenario, I find it’s not getting the desired air flow and I have to replace it with rigid after a testing period.
        Your opinion is always appreciated!

  15. I have a 1965 Minnesota home, two attics. Appreciate some tips / guidance on sealing & insulating one or both attics.

    Attic 1 is ~850 sq ft, pretty straight forward. Perfect rectangle, 2 gables (east & west sides), and 8 soffits (4 north, 4 south), no odd features on exterior roof. Attic 1 covers the majority of the 2 story house. No known issues here although open to reviewing energy improvements.

    Attic 2 is ~700 sq ft., perfect rectangle shape. 1 gable (west) and 6? soffits (3 north, 3 south). Attic 2 covers a heated Minnesota garage (set to 40 F in the winter), and also covers a back living room which is always cold, which is 2 steps down from the rest of the house so the cold air sinks here all winter (we encapsulated & insulated the crawl space under this living room last year which didn’t help with the temp). The back living room opens up to the rest of the house. We just converted wood to gas insert fireplace in the back living room to help with how cold it is.

    Attic 2 is fully insulated with a combo of batting and then blow-in (cellulose I believe).

    My concern now is attic 2, if all of this hot air from the new gas fireplace going to rise to attic 2 and then cause ice dams. I would like to improve the R value here. We added recessed lights to back living room 2 years ago so I already assume there are air leaks.

    Other than lighting fixtures & fans, how do I properly air-seal a standard attic? I.e. do I need to seal areas where the walls below reach the attic space, or around the perimeter?

    What about the ‘cat walk’ area in the attic? There are boards nailed to the floor here – do I need to lift them up or remove them to improve insulation?

    Lastly – any concerns with the chimney that runs through attic 2?

    • All good questions Adam.
      If it’s so cold in that one room in spite of ample insulation in the attic, I would first try to find the source of the cold. Otherwise, you might be putting a band-aid on the wrong thing. This can be something of a wild-goose-chase if you don’t go about it methodically.
      Personally, I would have that area of the house and the attic scanned with a thermal camera. This will help pinpoint the source of the problems, allowing you to address exactly the problem areas.
      While the thermal scan (also called an IR or infrared scan) will typically run $200-$300, it should save you far more than that in time and frustration trying to solve the problem haphazardly.
      It sounds like you’ve done the obvious things already, with insulation and air sealing. Attic access doors/hatches are notorious for letting warm air from the house into the attic, so you’ll want to look into a good solution for that. I’ve used the hatch covers from and they’re excellent! Simple yet effective. There are cheaper alternatives that don’t have anywhere the insulation capability or sturdiness, but I’d use something like this first.
      To find someone who can do the IR scan, do a Google search on “energy audit IR scan” with your city. I tried this with Minneapolis and turned up this:
      Is a company that looks like the type of inspector that I would prefer. They also have case studies on their website and descriptions that make it clear that the inspector probably knows what they’re doing. In fact, if they’re in your area, they look exactly like the type of company I’d use.

      I also found:
      which is an insulation company. They seem experienced, though usually I recommend going with an independent company that doesn’t sell insulation services in order to avoid conflicts of interest.

      • Thank you for your time and response!

        The attic hatch is in the garage and has a foam board box made of foil face r13.

        Like I said, the back living room is 2 steps down from the rest of the house so I think physics and cold air sinking are keeping it cooler. The wall in between the garage and living room is insulated too.

        The prior home owner said the attic 2 insulation was done in the 80s.

        Maybe I’ll try the thermal imaging.

        Lewis was actually recommended by an insulation supply company.

      • The depressed living room might have a slight effect on temperature but I don’t think it’s the source of the problem. Maybe it’s a cold concrete slab underneath?
        I misunderstood the attic insulation. I thought there was more. in your climate, you’ll want at least R-45, maybe more. That’s 15+ inches of normal insulation. So if you only have a few inches in the attic, that room will definitely lose a lot of heat.

  16. HI Ted,
    I could really use your professional advice on a house problem. We’ve lived in this 20 year old house for 3 years and when we moved in, it had a brand new roof. Last year we also installed a new HVAC with humidifer (which we are not running the humidifier because of the problem) and hot water heater (both gas). This winter, we noticed that there is frost / condensation on the inside roof of the attic. We had an energy audit and were told that we need to seal the attic and add insulation. Here is my question…we have had differing opinions on the sealing process.

    Contractor #1 – Only seals the fixtures and bigger holes, because he fears sealing the home up too tight and causing more issues. (Light fixtures, fire alarm, recessed lighting will be sealed)

    Contractor #2 – Has already done a blower door test. Will seal the entire attic and insulate (and install baffles). He will then do an exit blower door test and if necessary, install a bathroom vent that will run 24/7. (I really don’t want a fan that runs 24/7)

    Contractor #3 – Has read the blower door test of the other contractor. Will seal the entire attic and insulate (And install baffles). He says it is not necessary to do an exit blower door test because just by looking at my house and the initial blower test, there is no way that we will need an exhaust fan…the house will not be too tight after sealing. Also, he guarantees that there will be no frost in the attic after his work, whereas the other 2 can not give me a guarantee.

    I am so confused! I understand that we need to seal and insulate. However, which contractor’s advice would you go with? I really don’t want to have an exhaust fan that requires 24/7 venting. However, we need to fix this problem so our roof doesn’t rot! Any advice would be appreciated!

    • Contractor #2 sounds legit. #1 doesn’t know what he’s talking about. #2’s follow-up blower door test is required in many areas for your own safety to avoid carbon monoxide poisoning AND to ensure that the job improved the tightness of the attic. #3 is also not legit. You cannot just look and see. He might be right that your home is very leaky and it’s unlikely to need ventilation afterwards, however, as noted, current building science recommendations are to “test in, test out” for your own safety.

      As for #2, a continuous vent fan can be a great thing in a tight home, as having year-round fresh air is beneficial, especially in the winter when the air can get really stale. But the tests will tell how necessary that is. I’m assuming that you already have bath fans? If not, that should definitely be part of the job. I installed humidity sensors on my bath fans so they automatically run when the humidity is high in the bathroom. Almost nobody runs bath fans long enough after a shower to eliminate the excess moisture that can cause attic moisture buildup. I suggest 15-30 minutes after the shower is complete.


  17. Hi Ted,

    I also have been using the FUjitsu SLR for over six years now and all 8 units has been issue free. I do have a request of sort. These units are one all year round. I have tried to clean the fliter every season. I have two units near the kitchen and the fin is building up some grease inside register. Do you have instruction on howto remove the casing. i would like to clean the fins and the fan. I tried removing all the screws the eyes can see but the cover is not coming of. Please let me if you know of any video out that can show me howto remove it.

  18. Hi Ted,
    I am currently working with a contractor to add insulation to the attic of our house. We have decided to take out all of the old insulation (blow in on the floor of the attic) and do spray foam on the roof rafters instead. During removal of the blow-in he told us that he suggests doing new blow-in to cover up exposed plaster. He is afraid that the exposed plaster will be a perfect growing environment for mold. That said, I am skeptical that this is true, since the spray foam on the roof rafters should be creating a conditioned environment in the attic going forward, and therefore mold should not be an issue.

    Could you weigh in?

    • By the way, I read your advice about double insulation (it’s a case of more is worse), but wanted to confirm that given the exposed plaster fear

    • I believe you were intuition is correct. Personally I’ve never seen mold on plaster except in extreme environments. mold needs a growing medium on which to feed. plaster is not very tasty 🙂
      the main thing you want to do still is minimize the amount of moisture that might get trapped up in the attic, making sure that bathroom fans are properly vented and so forth. But as you said creating a conditioned environment in the Attic will minimize the possibility of condensation or other moisture related issues.
      one additional word of advice, people often recommend that a little bit of air from the heating slash cooling system is pumped into the attic space to keep that air from being totally stagnant. if there are already ducts running through there, then it’s pretty easy. if not, then just periodically check out the attic space during the winter to make sure no issues are arising.

      • Thank you for the quick response! As for your last piece of advice, would this simply be a single vent installed in a main area (landing area in the center of the second floor which is a ~1000 sq ft square with four bedrooms)? A crude drawing is below where x marks the spot.

        | BR | BR |
        | | |
        | BA | | BA |
        |______| |______|
        | BR | x | BR |
        | | | |

      • That drawing really did not come through! Sorry about that! I guess your imagination may have to do.

      • that’s okay, as long as you have some air flowing into the Attic to help condition it, that’s good. They say you don’t even need a return as there are almost always enough leaks to allow that small amount of the air to flow.
        a note to others who may be reading this – you only do this if you insulate Under The Roof so that the attic becomes a warm space of the house. if you have a conventionally insulated attic floor and you do this you will likely rot out the roof!

  19. Hello Ted,
    I came across your informative site during my research on Fujitsu mini-split heat pump system which I’m considering to install in my small house in Long Island, NY. It’s a tiny house with an oil boiler and copper line & fin-tube baseboard radiator around the perimeter that suffered the damage in recent freeze this winter. I’d like to remove this pipe & fin tube entirely and change the heating system to Fujitsu Halcyon Mini-split units for both heating and cooling. I was mainly looking at the Fujitsu system based on reading various sources on line but the HVAC contractor I found thru Fujitsu site actually recommends Mitsubishi system stating that it’s better system. Can anyone share their own experience with either of these systems? Any helpful insight would be greatly appreciated in advance,


    • First, I should say that while I haven’t personally used the newer Fujitsu models, I’ve heard they improved them considerably and greatly extended the warranty. I’ve had great luck with the two units that didn’t prematurely die…
      Much of the installation will depend on the number of rooms. Mitsubishi has a long history of being a workhorse. They also have multi-headed units, meaning one large outdoor unit with multiple indoor units, which allows for a more cost effective installation.
      With these systems, installation is extremely important so if your contractor is famililar with the Mitsubishi units, I’d go with that. Just make sure whomever you choose has had ample installation experience since these systems have very specific installation requirements.

  20. Hey I have found your article very informative. I fell like you have a very good understanding for the science behind the complexity of cathedral ceilings. I am a the owner of a roofing company. Currently I am in the office managing, but before I progressed to this position I used to be the installer / trainer and I have plenty of field experience. I have sought out as much training as possible during the life of my company to make my self the best installer and roofing compay in the community, educating as much as possible. We put our employees through regular training and re-certification requirements.Additionally we are members of a group of contractors who meet in the dc area for planning and training purposes. Basically I have been through hundreds of roofs and have several colleges from Chicago, Dc, Baltimore,and Boston who are all in the roofing industry and I feel you out of everything I have researched and everyone I have talked to you have the best understanding of cathedral ceilings. I especially like all the question with the responses. You really know your stuff!! Before I get into the detail of the situation is there any way I can attach a picture to this post?

  21. Hi Ted,

    We have been battling a leaky roof since moving into our home in 2009. Its a 1976 cedar A frame, with beams running length wise (along the wall). I should also mention that we are in northern Alberta where 40 below is the norm. Our leaking happens whenever we have a big freeze thaw cycle, and most of the water comes from the beams.

    We had a Interlock metal roof installed, and yet we still had leaking when we had a freeze thaw cycle. They came back and put in vents on one side of the roof, and yet again we still have the freeze thaw cycle leaking.

    Reading your article, I am assuming that due to the age of the home, the strong chance that there were squirrels in there messing around with the insulation at one point, and the fact that the ceiling is tongue and groove, that the moisture is freezing in the ceiling cavity itself and melting and dripping everywhere when it gets warm enough outside.

    My question is, to fix this can we install a hard board insulation from within directly over the ceiling itself? Taking down the old ceiling is a no go as it would honestly be easier to move. I was thinking that the hard board insulation would add extra insulation and create a new air tight barrier. Basically a hot roof with an older faulty insulated roof above it. Then on top of that, I could put up some Sheetrock or something else so long as I make sure to maintain that barrier.

    If that is an option, would I also wrap the beams, sealing the corners with a tuck tape of sorts?

    • the solution you mentioned is exactly what I would do if it were my home. preventing that air-born moisture from entering the roof cavity is key especially with the extreme temperatures you have. Any moisture at all is likely to freeze the moment it enters the cavity and then as you noticed thaw out and rain down on you.
      beams are the challenge. you might want to use low expansion spray foam to seal the areas where they penetrate the walls or ceiling, so as to make an airtight barrier. wrapping them with insulation board could also helped provide a thermal barrier because they may be transmitting the cold into the house leading to condensation on the cold parts of the beams.
      once you’re all done sealing and insulating then like you said adding a layer of sheetrock to everything on the inside provides the added barrier that should stop virtually all moisture from entering the roof cavity.

      • Excellent. Is there a brand, type, r value, or specific material I should be looking for in a hard board?

        And thank you for the prompt response.

      • the most of the available and cost-effective is either the blue board or pink board hard foam insulation. however you might consider foil faced polyiso board film. the foil facing can be taped with metal tape and forms a 100% moisture impermeable barrier. it also has the highest R-value per inch of thickness which I’m sure you could appreciate in your climate.

      • And hopefully the last question I have. I re read both your posts and noted that on cathedral ceilings you mention 2 things counterintuitive to sealing up from within with hardboard. That you absolutely don’t want to trap moisture on the cold side of the insulation, and that you need a 2” gap between the roof and the insulation.

        My train of thought is telling me that by sealing from within with hardboard, i am trapping moisture on the cold side of the roof. I am also thinking that if I am putting this hardboard directly on the ceiling tongue and grove panels that I am not leaving a gap.

        I am assuming this isn’t an issue because there still should be adequate ventilation through the old roof? I just wanted to confirm if my logic was still sound. Thank you again.

      • that’s the theory. By sealing off the inside, you are preventing or moisture from entering the cavity. so it’s only moisture that flows into the roof cavity above from outside. and that moisture during the winter is extremely low because of the cold air. In fact there is virtually zero water content in air that cold.

  22. Hi Ted, I bought my house about 3 years ago, I noticed that there are no vents anywhere in the roof or under the eaves there’s also no insulation in the attic. I haven’t had a moisture problem since moving in but would like to insulate up there due to the chilly Pacific NW weather. Would putting the insulation in potentially cause a moisture problem? And should I put vents in prior to insulating? Thanks for the time,

    • You ask a great question because unintended consequences can occur, especially in very humid climates.
      Often, uninsulated homes show no signs of moisture problems because much of the heat escapes into the attic, keeping it warmer than it would be if it were insulated. The warmth helps prevent condensation which is a big cause of moisture buildup, mold, etc.
      When you insulate the attic floor in order to reduce heat loss that will, by design, reduce the temperature of the attic, making it more prone to condensation.
      Having said that, the trick in very humid climates is that a highly ventilated attic allows outside moisture to enter and saturate the interior of the attic. As the temperature drops at night, much of that moisture remains in the attic leading the “fog” to turn into water droplets which can literally rain in the attic.
      Here’s a detailed post that discusses this

      The tl;dr version is that even in a completely ventilated attic, you can have moisture problems in this climate due to natural humidity and nighttime cooling.

      The conclusion is that it can be better to insulate the attic as if it were part of the living space, closing it up (no ventilation at all) and using moisture impermeable insulation (like rigid foam board or high density spray foam) to insulate all the surfaces that are adjacent to the outside. More specifically, insulate the gable walls and the underside of the roof, just as you would if this were a room INSIDE the house and the roof were a cathedral ceiling.

      If you can’t do this, and you don’t have moisture problems, you might create them by insulating the floor of the attic.

      Hope this helps you from some heartache in the future.

  23. Looking for advice on ceiling mount cassette mini split We have a remodel in process and are using a mini split for an added bedroom. The wall mounts are aesthetically not pleasing to my wife and I. HVAC installer is advising against ceiling mount primarily due to noise associated with the condensation pump as in smaller unit it will tend to run more often. Only 8 foot ceiling in an older home the unit would go in. No drop ceiling so ceiling joists would have to be cut and a box for mounting created. Does not appear we would have enough pitch to gravity feed condensate. Any thoughts and or advice would be appreciated. Looking at Daikin Vista series unit. Attic space is limited also so that is a possible issue. Square footage of room is about 400.

    • I’d be surprised if the condensate pump was that noisy. it should just be a tiny pump. the best thing for you to do is to get some references from the installer of other people who have these units and see if one might be willing to let you listen to it in operation. all the units I have personal experience with have gravity feed for the condensation. the question is, what is the alternative? if you don’t like the look of the wall units, then it seems like your options are very limited for this small a space.

  24. What could make a house extremely dusty after replacing the heat pump with an a/c and replacing the furnace coil? The furnace filters don’t get dirty like they did before, in fact they look new, so it appears the dust is bypassing them. We always had normal dust (meaning the same amount I had in the house before) in the 11 years since building the house until now. I even have dust in my storage room where the furnace is located. That never happened before at least not at the point where I felt I had to dust my storage tubs. We first noticed it last winter after the new a/c. The HVAC company contributed it to the ultrasonic humidifier. We got rid of it and it did improve considerably but it is still bad just not egregious. I have to dust days before entertaining because you can write your name on the surfaces after 4-5 days. I am at a loss as to why this change would have made a difference. Any ideas?

    • There’s a good chance when they replaced the heat pump and AC coil that they didn’t seal the unit well and it’s sucking in air from the dirty space in which the unit is mounted, bypassing the filter.
      Make sure the filter has a snugly fitting door over the slot the filter goes into, if you have that type of setup.
      Check the air handler for gaps where the sheet metal from the ducts come together. It’s quite possible that that is not sealed well (most aren’t).

  25. Hi Ted,

    I have a 1978 ranch home in northern Illinois that has prefabricated trusses for a roof. Where the truss ends sit on the top plate of the exterior walls, and the top and bottom plate of the truss join, they form a triangle of solid wood from the interior ceiling to the roof sheathing. We have one bathroom on an exterior wall, where we incur condensation and sheet rock damage on the ceiling, every 16″ on the truss cords starting at the exterior wall and coming about 3-6″ in, because the truss corners are creating a solid wood thermal bridge. The attic is very well insulated with deep blown-in insulation, but no amount of insulation in the attic can change the solid wood thermal bridge. The bathroom also already has a ceiling fan that vents to the roof and is operating correctly.

    My solution I am thinking of(because we are gutting the bathroom anyway), is to take down the sheet rock ceiling, sheet the entire interior ceiling in the bathroom up against the trusses in 1″ of rigid XPS foam, seal the joints tightly, then sheet rock over it again. Is this advisable? Will 1″ of XPS be enough to stop the thermal bridging through the wood? I’d really like to avoid losing much more than 1″ of ceiling height.

    If I didn’t explain that well, here is a link to a picture of what I’m talking about.

    • That makes perfect sense. As you described, all that wood makes a thermal bridge, transmitting the cold right into your ceiling. I think installing a thermal break in the way you’re describing could work well. You could get even more R-value per inch by using polyiso board foam. With R-7, it’s highly unlikely that you’d experience the condensation issues any more.

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