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,
    Good evening and thanks for all the outstanding information! Wife and I purchased an older home on the panhandle of Florida. We have vaulted ceilings in the living and dining room, that flow into the kitchen which is a 10 foot ceiling. The ceiling in that area is a tongue and groove juniper planks. It is gorgeous and we love the look. It was one of several selling points for us. Our attic is currently insulated under the roof deck with foam. There is no batting or blow in insulation on the ceiling surface. We also do not have soffit or ridge vents. The tongue and groove is nailed directly to the roof rafters, so there are substantial gaps for air flow from the interior of our home, in to the attic space. I had intentions of installing blow in insulation on the back side of the tongue and groove so that we aren’t cooling/heating the attic space as well. I mentioned to a friend and he said it might not be a good idea and it may not be insulated for a reason. Reading through your blog, I see that may in fact be the case and was hoping to hit you up first hand. I appreciate any advice you are able to offer!

    • In your climate, there’s much less concern about condensation, which is usually the killer of this type of construction in colder areas. However, one would still want good insulation and air sealing for comfort and energy efficiency.
      If the attic is already insulated with foam, then they considered everything below that to be the “conditioned space” of the house. As long as the quantity of insulation used is sufficient, then you shouldn’t need to add insulation to the T&G. The attic space, insulated like this, is already part of the interior living space of the house.
      As for the venting, when you insulate with foam below the roof deck, ventilation in the attic would be counterproductive. It would be the same as opening the windows of the house. It would actually do more harm than good. Attic ventilation is only used when the insulation is on the attic floor.
      So, based on your description of the existing construction, there shouldn’t be any reason for changing anything.

  2. Dear Ted, what is your opinion on concrete sealant to reduce concrete dust in an unfinished basement? My understanding, based on reading various building science materials, is that painting concrete -either with latex paint or with something like dry-lol- in the basement is not a good idea because it can trap moisture in the concrete. Does this also apply to concrete sealant (I saw rustoleum makes one) in the concrete floors? And what about lime-washing basement walls to brighten them up while keeping them breathing? Thank you so much for your thoughts!

    • Hi Liz, that’s a good question. Usually, they want to put a water/vapor barrier down underneath of the slab floor, but you’re right – if you water seal the top, you’ll impede the natural motion of water vapor up and through.
      However, I’ve seen many people epoxy coat slab floors with no ill effect.
      I’d suggest doing a test to see how much moisture is working its way through the slab before doing any sealing. The test is simple:
      – Cut a 3’x3′ piece of transparent plastic sheeting (like they sell for tarps)
      – Tape it securely (the entire perimeter) to the concrete floor. Several test locations would be best. The goal is to make a waterproof seal around the plastic
      – Wait a week to see what happens. If enough moisture is migrating through, you’ll see condensation forming under the plastic sheet.

      This is a simple test but it gives you a good measure as to the amount of moisture moving through the slab. If the plastic gets wet in the first day, it’s a lot of moisture. If it take a week or two (or never), then it’s considerably less wet.
      If the test shows high moisture conditions, you’ll find that any surface coating will get “blown off” by the underlying water pressure. It’s slow, but persistent. It may also be very difficult to get anything to stick to it. On the other hand, if the test shows no moisture, then you should have little problems with it.
      As for the walls, there shouldn’t be a problem doing that. The moisture will slowly work its way through, carrying the lime so they’ll stain again over time. But no reason you can’t beautify them.

      • Thanks, Ted! I was also looking at something called concrete densifiers as reducing basement dust-my understanding is, they work by penetrating the concrete surface with particles that bind the concrete together, making it stronger and less dusty. I wonder if a product like that would work to keep the dust down while still letting moisture through?
        Thanks for your thoughts, Ted. This blog is a wonderful resource!

      • I’ll start with a disclaimer – I was not familiar with concrete densifiers, so my thoughts are based on a quick review of the literature.
        Based on your initial question and the description of densifiers, this process appears to be a great solution for your concrete dust issue. It seem that they were designed exactly for this purpose.
        Since this is the first process in the advanced concrete polishing techniques that are widely used these days, it has to be compatible with slab floors. If it caused problems with moisture, there would undoubtedly be some mention of it, and I couldn’t find any such complaints.

  3. Hi Ted,
    We purchased a small one- story lakefront cottage in Northern Michigan which is used only from June through September. Although the cottage has baseboard electric heat, the pipes are drained in the fall, and the cottage remains empty and unheated over the winter. There is no air conditioning. We installed a vapor barrier in the crawl space under the cottage. Fiberglass batt insulation in the attic has mold, which is not surprising because the bathroom fan vents into the attic. The cottage, which has wood siding, was built in 1970. The roof has a ridge vent and 3 inch circle vents in soffits every 2 feet. Gable vents at each end of the house have been blocked by our contractor so that the ridge vent and soffits will work better, he said. We are removing the moldy insulation this spring, and will let the attic air out over the summer. In the fall we are scheduled to redo the bathroom, which will include a tile shower and a new fan – venting to the outside! Our contractor proposes to add cellulose insulation in the attic in the fall after the bathroom renovation is done. But, if we don’t heat or air condition, do we need to insulate? If so, should we first put in any vapor barrier in the attic, and is cellulose the best insulation to use for our situation? The attic is not used for any purpose. Should the insulation be on the floor of the attic? Will appreciate your views on this. Many thanks!

    • Sounds like a lovely cottage on the lake.
      So a few things. Those 3″ soffit vents are worthless, when you look at the actual amount of air they allow to flow. Homes used gable vents for decades (centuries?) very effectively. Soffit-ridge vents are good in theory but are rarely implemented properly. That said, if you air-seal the attic floor (i.e. make sure all the holes between the living space and the attic are closed) and the bath fan is properly routed, you’re unlikely to have future problems since you’re not even using the house during the really cold months. If you shut the house down and it’s just cold during the unused months, then the humidity inside the house will be very low, assuming the crawl space vapor barrier is doing its job. With very low interior humidity, there’s nothing to get into the attic to cause problems. In fact, the air in the house would be basically the same humidity as the air outside that is being used to ventilate the attic through the soffit-ridge vents.
      As for insulation type, cellulose is fine, easy and relatively inexpensive. It will keep you from getting uncomfortably hot on sunny summer days. Just make sure that the floor of the attic is checked and sealed after the fiberglass is removed and before the cellulose is blown in because once that cellulose is in there, it’s virtually impossible to do anything in the attic.

      • Ted, curious if have any prior posts or advice on preventing ice dams…

        Last summer (with your advice!) we had a home energy audit done to help with a drafty room, get house ready for the next 20+ years, and ideally stop some minor ice dams from forming on a north facing gutter (the roof is about as basic as it gets).

        We ended up fixing some bathroom vents that were incorrect in the attic, sealing the attic / bypasses, installing insulation dam, installing chutes, and doubling R value. Not bad!

        The past month (in Minnesota) has been awful with ice dams, some neighbors have gutter to ground icicles and it’s all over the news. Our roof now has a solid 20″ of snow on it, and you can’t even see the bathroom vents on the roofline as they are buried.

        Our house was doing really really well with zero ice dam issues. I was hoping to ‘pressure test’ the house and not use my roof rake once this winter. Unfortunately some minor ice and icicles start to form on a separate north facing gutter. so I went ahead and scraped the snow off.

        What else can I possibly do to prevent these from forming? Should sofits be inspected / cleared, or should I consider double checking the attic work this spring?

      • Glad to hear of your successes! It sounds like you’re doing quite well given the extreme conditions.
        The trouble is, with that much long term snow on the roof, some snow melt is inevitable. However, let’s see if we can help you track down the last little heat leaks that might be causing the localized melt/ice that you’re seeing.
        The first thing I’d do is take photos around the perimeter of your house in order to document the locations for future reference. Then, when you check the attic, you will know the area to search for “heat leaks”. It could be anywhere along the line from the gutter where the ice is on up to the peak of the roof where the snow is melting. Then you’d inspect the area underneath that (the attic floor) to ensure the insulation looks good and there’s no sign of air leaking from the house to the attic. The giveaway for this is darkened insulation. As air moves through the insulation, it traps dust, blackening it. However, since you added insulation recently, it may not have had a time to collect dust, but it’s worth a look.
        If there’s nothing obvious like that, you might see if there are any drain line vent pipes coming up through the insulation and up to the roof. Those pipes usually have big holes in the attic floor that they come up through. A little canned foam goes a long way to sealing up those problems.
        Anything else that causes a hole between the living space and attic, like fans, lights, electrical boxes, etc are also things to look for. Recessed lights, even efficient ones, generate a fair amount of heat. That heat can rise up into the attic leading to snow melt.
        A final thing that occurs to me is HVAC ductwork in the attic. If you have forced air heat and ducts in the attic, that would definitely leak some heat into the attic, even if insulated and sealed. So look for anything like that. Even if you only have air conditioning, there can be enough natural air movement through the ducts to carry living area heat into the attic.
        Hope that helps. Good luck and stay cozy!

    • Hello Ted, I have a 1834 Vermont home that is 16×38. The house has two gable windows, standing seam roof with no insulation. I purchased the house gutted and will be using it as a getaway ski home. Parts of the house are post and beam and the newer parts are balloon frame. The exposed rafters look great and I hate to enclose them. Im debating on putting insulation in the walls do to potential moisture problems. I plan on closing the walls up but not sure about the ceiling. The heat is a wood stove. I also will be using a tankless water heater for water. Your thoughts would be appreciated.

      • Hi Joe, that house sounds like a real find!
        Given the vintage of that house and the planned usage, I’m hesitant to give specific advice for fear of leading you astray – there are just too many possibilities. You are right to be hesitant to make changes. The house has lasted that long as-is, and there can be “unintended consequences” of making dramatic thermodynamic changes to the home. As you noted, moisture issues are an important consideration.
        My best suggestion would be to consult a local builder who might have experience with houses like that in your area. Sorry that I can’t be give you more guidance.

      • Ted,
        are there benefits to just installing interior tongue and groove on the walls with no insulation and leaving the vaulted ceiling alone? Again, its about 630sqft.

      • The T&G would just be for aesthetic purposes. Otherwise, it serves little purpose. However, if you’re going to do that, you could safely put foam insulation board behind the T&G. Normally I only suggest this if someone’s doing a gut/remodel including windows and doors because the added thickness of the insulation (usually 1″-2″) requires extending window and door jambs. If you are thinking about T&G interior, you’d have to extend the jambs anyway.
        Since the foam insulation would be interior to the existing balloon framed walls, it wouldn’t mess with the dynamics of the wall space other than allowing it to get colder (since the heat from the interior would be greatly reduced by the insulation). The insulation board also acts as an air and moisture barrier, which greatly reduces the chance of moisture getting into the walls. Just be careful air sealing around sockets and other holes that might need to be cut in the insulation.
        Or if insulation really isn’t important, then you could just add the T&G to the walls. But if it’s a ski lodge, I’d think you would want some insulation.

  4. Can you recommend an air quality test kit for dust and fibers. We live in a fairly new condominium and have an incredible amount of dust and fibers on all of the surfaces and in the vacuum cleaner every time we use it.

    • Sorry, I’m not familiar with DIY tests. I always referred clients to a specialist back in the day before these kits were available. Nowadays, home tests are undoubtedly available that can do the trick but since I haven’t personally evaluated any, I wouldn’t want to make any recommendations.

      • Hi Ted!
        We are currently working with a homeowner that has a flat to mansard roofing system on their home. We have redone the shingles and the rubber membrane on the flat portion. We have also replaced the drains from the main flat roof to exist through the piping system in the attic crawl space and come out through specialized downspouts. We have added heat cables in the gutters and specialized cables spread across the flat roof. This has eliminated the standing water and ice dams on the roof.
        We are now battling with an extreme moisture issue in the attic crawl space. The space is only just over 3’ tall (42”), this is between the main home and the flat roof. Minimal intake (4) and outtake (4).
        There is a lack of insulation, as seen in the pictures provided. There is active sweating of the pipes, causing mold to form on the supporting members. There are areas were there is 0-1” of insulation and areas that have 3’ of insulation, there is also no vapor barrier. The mansard boards are uninsulated and sweat excessively as well. the porches have the wainscot type of ceiling, no ventilation and little insulation, these areas seem to have the most mold on and moisture on the supporting members and beams.
        We would like to oil seal the decking on the mansard sections, from the inside and install insulation to the attic crawl space. If we did seal the mansard, then put in insulation, would this prevent the moisture and mold from causing a green-house effect?
        Any recommendations would be greatly appreciated.
        If you would email us, we have tons of pictures of the property and the space we are looking to remediate.

      • Ray – try emailing me the images directly – WordPress strips out links so I can’t see the images you linked to. You can send email to tedinoue which is a address.
        It sounds like a challenging situation. The biggest thing at this point is to determine why it is so humid and moldy in there. That humidity has got to be coming from somewhere. We can go into the gory details privately via email.

  5. Hi Ted,
    Hope all is well. I messaged you about a month ago about a flat roofed, 3-season room I’m converting into a heated/ac room. Things have changed a bit since I last spoke to you, so I wanted to pick your brain over a few things…….The original ceiling had a 3″ slope with 2 x 6″ rafters. Ceiling was 8′ high at one end and 8’3″ at the other. I wound up running 2×4’s from the 8′ end to the 8’3″ end to increase the rafter depth, but I didn’t follow the slope. The ceiling is now flat. The whole ceiling is now approx. 7’9″ high. And I now have a rafter depth of approx. 9″ at one end and a gradual increase to approx. 13″ at the other. (I hope I’m making this clear). I’m going with an unvented assembly as is recommended with a flat roof. I do not have any vents in the soffit and the attic is sealed. I plan on putting 2 layers of rockwool r-15 in the ceiling. That should give me 7 inches of insulation. I put baffles on the first 4′ of roof sheathing where the rafter depth is only 9″ to keep the insulation from touching the sheathing. I have already started and plan on taking the time to thoroughly make the drywall air-tight. My theory here is my air-tight drywall will be my air barrier and the paint/primer will be my vapor barrier. My question is, half of the rafter space will have 4″-6″ of uninsulated space above the rockwool. Is that ok to have with an unvented space or should that be fully filled up? Also 2nd question, the attic is easily accessible to. Would it be a positive or negative for this rafter space to vent into the attic? And of course 3rd question is, Do you see anything else wrong with my plan?

    • having an air gap between the insulation and roof sheathing is the safest way as it will minimize moisture from being trapped in the insulation and held against the sheathing. Imagine the insulation as a sponge. If you hold that wet sponge against a surface, it will take a long time for the water to evaporate and dry out, so the surface will stay wet. If there’s a gap, then the sponge will dry out much more quickly and the sheathing will be much less likely to get damaged.
      This is all precautionary since you’re sealing it up to prevent moisture from getting in there in the first place, but it’s always a good idea to have a second line of protection.

  6. Hi Ted,
    Several years ago, I had an addition (4-season room) put on my house. With the intention of it being our sunroom, we had large windows installed around the east, south and west sides of the addition (attached to the main house on the north side). The addition was sunny, warm, dry and just what we wanted. However, recent observations have me concerned.
    Unbeknownst to me at the time of construction the builder never caulked the windows. When the rain blows in a certain direction water must be penetrating the envelop. I say this because there are areas outside the interior walls of the room that appears to have black mold growing.
    Being retired and without unlimited funds, I plan to repair the damage myself. My question to you is: what should be my sequence of steps for remediation, and do you have any suggestions (beyond caulking) as far as materials, procedures, concerns, etc.?
    Thanks for your time and sharing your expertise.
    Tom W.

    • I’m sorry to hear about the problems you’ve found.
      I don’t understand what you mean when you say: “areas outside the interior walls of the room that appears to have black mold growing.”
      Are you seeing the walls inside the room or on the exterior walls?

      If it’s on the interior walls of the room, there are a variety of possibilities:
      1) it could be the insulation is inadequate and/or heating in some areas, allowing the walls to get cold enough for condensation to form repeatedly
      2) it could be, as you note, moisture getting into the walls and saturating the drywall.

      If it’s problem 1, then keeping the room warmer and drier would help. If it’s problem 2, you’re in trouble and should open the wall up to inspect for interior damage.

      With problem 2 (wet walls) then the drywall will become unsound. I had this in my sunroom, exactly what you noted, where water got into the walls. Over time, the walls rotted out from the inside. I could poke my finger right through the drywall.

      Try tapping on the wall with your finger. Does it sound dull and feel mushy? If so, you’ll need to carefully cut out some of the drywall to inspect the interior of the wall. In my case, the wall framing was completely rotted out and had to be replaced with weatherproof pressure treated lumber.

      Check the condition of the wall and check back and we can walk through the issue.
      In the meantime, also check the exterior area above where you’re seeing the possible mold. You might find some obvious areas where the flashing or water sealing is improperly done.

      • I think more info is needed. Is the problem inside or outside?  “Areas outside the interior walls” almost a double negative. What type of siding was installed.  Caulking around the windows???  The main question is very weak on exact details. Ted, Thanks for all you do.

        Rick Hirsch Hirsweet Aussies Rick’s Southwest Mercantile

        (936) 661-9093

      • Hi Ted – thanks for replying so quickly and sorry about not being clear enough in my original description. I’ll try to clear up the confusion with a couple pics.

        First-off, the room in question was built off the upper story of the house. As a result I can see the underside of the floor joists (seen here covered with plywood). The pic below was taken looking up from the ground toward the sky. Notice the black staining on the plywood.

        The pic below was taken from inside the room (just above the first pic. Notice there are no water stains or mold showing on the interior wall itself. However, there is a dark area where the base molding and the floor/rug meet. About 1 sq. ft. of the floor in from of this dark spot is soft (indicating the wood might be rotted).

        What I meant by “areas outside the interior walls of the room that appears to have black mold growing.” Is simply the wall cavity. I should have used that terminology originally. No mold can be seen looking from outside (i.e. the vinyl siding) or the inside (i.e. drywall).

        I think the only thing left is for me to start ripping out the drywall and insulation to see just how far the damage has gotten. Worst case will include the flooring/joists/studs until I eliminate the mold, but I’m keeping my fingers crossed that I’ll be pleasantly surprised.

        As always, thanks for sharing your knowledge. If anything else comes to mind (products, procedures, recommendations, warnings) ….. I’m all ears. 😊

        Tom W.

        Sent from Mail for Windows 10

      • OK, I understand better now. I’m afraid your photos didn’t come through but your explanation is clear now. I do agree that the next step is going to be some explorative demolition. Drywall is easy and cheap, so starting at the exterior wall to see if you can find the source of the leak is a starting point. It might just be one “little” opening that’s allowing water to drip into the cavity. Over time, that can cause huge issues, so it’s good that you’re finding it now. Good luck. Feel free to drop a line with any additional questions.

      • Figured I’d resend the pics as attachments instead of intermixed with the text. Hopefully what I was saying is even more clear with the visual aid.

        Sent from Mail for Windows 10

  7. Ted: Live in Northern Wisconsin and have a T&G ceiling. When the temp. gets to 34degs. I get water in several places inside. The roof has full ridge vent and soffits with shuts. Fiberglass insulation with one inch sheet foam over that and seams are taped, and then T&G is applied. The ceiling lights are LED and boxes were caulked. But still have a problem. Should the foam sheets be caulked around the outer edges? Live in Minocqua,WI do you know of a Green Builder?
    331-442-1202 Thanks, Jack

    • Hi Jack. Your situation sounds very similar to Mike’s (just before yours). Mike suggested that this phenomenon might occur because the humidity that got in there during the colder weather was freezing. Then, when it got above freezing, the ice would melt and drip down.
      The trick is, how is moisture getting in there? A question for you – have you observed that the drips occur in a place that makes sense based on position of the light? That is, are the fixtures directly below the locations of the drips? Or are the drips occurring at the lights?
      I’ll see if I can find someone in your area that looks promising and post a followup.

  8. Hi Ted. Appreciate your expertise. We live in Canada (BC). Inside relative humidity hovers around 45% in our house. We have a cathedral ceiling, 2×12 rafters. There are recessed lights. Built in 2012. Above the drywall, which is screwed to the rafters, there is a vapor barrier, then R38 fibreglass insulation, then styrofoam ventilation baffles and then the bottom side of the OSB roof sheeting. There is an exposed beam, mid-way down the rafters on one side of the asymetrical roof. There is also a beam at the peak of the roof. Along both of these exposed wood beams, the vapor barrier does not cover the beam itself, but instead was cut along the beams and continued on the other side of the beams. Every year, after a cold snap, we have a few water drops and staining on one of the interior exposed beams, above 2 windows, and as well, down the front of the Hardi plank siding on the exterior front of the house, directly under and corresponding to the rafter bays. No reason to believe the roof is leaking. This phenomenon is only apparent in late winter, when things are starting to warm up outside. There are aluminum soffits at the bottom of the rafter bays, and ridge venting at the top. The building inspector passed everything at the time of building, but clearly something is wrong here. I suspect that warm moist air has become trapped above the insulation and below the roof sheeting, condensing and then freezing like little stalactites on the cold underside of the roof sheeting, then melting with the warming weather, and dripping down the styrofoam baffles and/or the vapor barrier, eventually escaping first chance it gets- hence the water droplets and staining on the beam, above the 2 windows, and down the siding. I’m very concerned about the insulation likely being saturated, by this point, and certainly concerned about the roof sheeting and the rafters rotting. Look forward to your advice for remedying this very stressful situation. Thanks in advance,

    • Sorry for the delay in responding.
      From what you describe, I agree with your analysis, though it might not be so bad. It’s certainly possible that the humid air is continuously getting into the cavity and freezing, and you’re seeing a thaw phenomenon. But it may also just be that the condensation is only an issue as it warms up and the outside. During those periods, the air that is ventilating the roof cavity is itself full of moisture, and that moisture is condensing on the cold beams, leading to the drip. However, as you noted, there’s enough condensation that it’s running down the cavity and out the soffits, which is concerning.
      In the best scenario, there’s little to worry about with a little bit of condensation which evaporates quickly, However, if it happens frequently and doesn’t dry out, that would be a problem.
      If it were my house, I would inspect that cavity for extensive moisture buildup. The easiest approach might be to go up through the soffit where the staining is observed. Snake a camera in there to inspect visually (you should be able to find an inspector with a suitable camera setup.) I would also want to do a moisture scan along that rafter bay to test the insulation for moisture buildup. There are moisture meters that have long probes that can measure the moisture inside of the cavity. They require drilling a couple of 1/4″ holes, but those are easily filled.
      That would be the start – determine if it’s a big problem or not.
      If there’s moisture throughout the cavity and you feel that it’s coming from the gaps around the beams, you might have to do more to air-seal the connection around the beam. I’d be tempted to caulk and foam around those joints then put some decorative trim over it.
      Worst case scenario might involve tearing off roofing near the beam in order to have a full visual inspection, then taking remediation measures from the roof side (probably heavy spray foam all around where air would get in around the beam.)

  9. So I have been reading about cathedral ceilings here and elsewhere. Here is my situation. I live in a log home 3000 sqft on the north east coast. The living space has cathedral with an 1 inch foam board and R19 bats on top of that. The bedrooms have only R19 bats un faced – no rigid boards. All ceilings have 1/2″ tongue and groove pine boards. The roof has ridge vents with soffit vents all around the edges.
    There is a roof fan on the roof to ease the heat in summer from the attic triggered by a T-Stat and it pulls air through the soffits and the T&G. The T&G boards leak warm air from the house into the attic as they are drafty and are attached directly to the rafters.

    I do not have a whole house humidifier, the forced air furnace is dry. Bathrooms vents to the outside through the roof.

    The bats are beginning to compress, I assume moisture and age perhaps and I need to improve the insulation by adding or removing and replacing.

    1) Loose blown insulation: – but this absorbs moisture and can create a mess by penetrating through the seams of the T&G boards or along the walls where there is a seem. ( I expect to caulk that soon) in the bedrooms. Blown insulation is just messy, and my least favored option.

    2) Remove bats and install water proof close cell foam on the bedroom side applied directly to the T&B boards and then Fiberglass bats on top. My assumption this foam will stick to the T&G and create a tight water vapor retardant? But I am not sure, can you chime in?

    A bigger problem is the Cathedral ceilings. Its difficult to reach and insulate and can only be reached from the outside by removing part of the roof and insulating. But there is a 40 yr asphalt roof with 20 yrs more to go on it and that’s going to be very expensive to deal with. The entire roof size is 60 squares (6000 sqft). In the past, I was able to squeeze into that area , at the peak but I don’t think its any possible to spray foam there. ideas?

    • That’s truly a challenging construction above the bedrooms. The T&G as you noted provides minimal air barrier so your warm air and indoor humidity is going to float right up through the cracks. Caulking may help, but it may not because it’s so difficult to truly seal wood seams given all the expansion and contraction wood goes through as temperature and humidity changes. You could spend a lot of time doing that with little benefit.
      I like the idea of spray foam from the top but to do it properly, you’d have to rip off the entire roof. If you only had a couple years left, I’d say go for it, but with a lot of life left, that would be a bitter pill to swallow!
      How about a somewhat radical idea – add nailers across the T&G ceiling, maybe 2×2’s, spaced 2′ apart. Fill in those 2′ spaces with board foam then add full 4×8′ sheets, maybe 1/2″ thick on top of that, to provide an air and moisture barrier. Then, put a new layer of T&G or whatever interior finish you want. You’ve now virtually eliminated the air/moisture problem so your bedrooms will feel much more comfortable and energy efficient, the insulation will be better, and the chance of moisture problems will have decreased dramatically.
      This would be the easiest solution that I can think of. Compared to ripping off the entire roof and spray foaming, there’s no contest. Or, compared to ripping down the existing T&G and re-insulating above it, again, no contest.

      • Hmm, So the bedrooms ceiling is flat, I can get there and spray foam on from the attic floor. This way I don’t have to tear anything up, just clean up of leak through foam on the T&G interior side. Then the T&G remains beautiful. Do you think that the foam would seal the T&G this way properly?

        On the other part of the house (Cathedral side), I am seriously thinking through your “radical idea”. But you have given me another idea, There are faux pine beams for show, 7 ” thick below the T&G , spaced out every 3 ft, I may be able to foam from the inside over the T&G giving me approx 6R X 6″ = 36R. Then I can nail a foam board over that if necessary and add T&G or sheet rock after. Thoughts?

      • aha, I misunderstood. If you have access from the attic, then spraying foam from that side would definitely be the method of choice. Even a thin layer will airseal the T&G from behind, greatly improving the situation. You could then add insulation on top of the foam, like blown in cellulose, without worrying so much about the dust getting into the house. But I wouldn’t use loose fill in the attic if you plan on going up there because it’s so messy. A few inches of foam would be best.
        Your suggestion for the cathedral side sounds great since you’ve got those beams there. Everything would be tightly sealed and give good insulation and a working surface for the new interior ceiling.

  10. I live in the Hudson Valley NY in a ranch style house with decent insulation. I’ll be installing about 5 KW of solar panels myself with a grid-tied inverter. I have baseboard heat with an oil fired boiler. I’d like to go all electric (baseboard heat and on-demand water heater). I’m an electrical engineer so I would do all the wiring and install myself to save money. Have you heard of anyone that has done so with good results? Would the energy savings from solar help offset the higher electrical usage and make it financially feasible? I’m paying like $3000 in oil per year. Also, do you have an opinion on the new Dandelion Energy Geothermal systems? Thank you very much for all your tips.

    • Electric baseboard heat is very energy hungry. However, it’s also about the least expensive thing to install.
      Let’s go through a simple BTU calculation using the numbers you gave and estimates for energy costs. You can adapt to your own costs to see how the numbers work in your case.
      Electricity cost: $0.15/kWh
      Heating oil cost: $3.00/gallon
      Electric baseboard is 100% efficient, producing 3412 BTUs per kilowatt-hour
      Oil boilers might give you a delivered efficiency of 80%. 1 gallon of heating oil contains ~139,000 BTUs. At 80% efficiency, that’s 111,000 BTUs per gallon.
      If you use 1000 gallons for the winter, that’s 1000 * 111,000 = 111 million BTUs
      Converting that to electric heat:
      111,000,000 / 3412 ~= 32500kWh
      at a cost of 32,500 * $0.15 = $4879.

      From a financial perspective based on the raw energy costs, it’s much more expensive to heat with baseboard electric than with the oil you already have.
      However, a very viable option is to use heat pumps. The up-front cost however is much higher than the electric baseboard, but the cost savings could be amortized over a number of years. A heat pump, in round numbers, will give you about 3x the heat per kWh as baseboard electric. So if you could get all your heat from heat pumps, the electric cost to run would be about $1600, saving you about $1400/year in oil costs.
      Nothing is simple though. In the Hudson Valley, you get many cold days (e.g. average temperature below 30F). At these temperatures, you might be running the heat pump along with your baseboard oil heat as a “supplemental heating”. This is exactly how I run my own house. Baseboard hot water from a propane fired boiler. Primary heating through both geothermal and mini-split heat pumps.
      You’d have to run your own numbers as these are quick estimates.
      Since I’m not in the business day-to-day anymore, I’m not familiar with the Dandelion system. Pretty much, geothermal systems are limited by physics, so you may find the mechanical systems vary, but the general technology is the same.
      What I will tell you is that it is absolutely critical to get an experienced pro for installation of the geothermal system. There are a lot of Johnny-come-lately HVAC technicians who are making a lot of money off of geothermal systems but who know nothing of the physics and importance of the installation. So if you go that route, make sure that your installer has installed systems for many years and has good references. You don’t want to spend $20k-$40k on a geothermal that ends up not working up to spec because the loops weren’t installed correctly!

      Hope that helps.

      • Good Afternoon. We had the insulation completely ripped out of our house and replaced. Now our it is extremely uncomfortable. The hard wood furniture is chipping, peeling, and fading all over our house. There tooling in our attached garage has rust all over them. We have paid a lot of money to have this fixed and now it worse. We live in Philadelphia Area. I took infrared pictures and there are blue spots all over. I really just want to get it fixed somehow! I appreciate your help.

        Rick McGovern

      • Hi Rick, I’ll post a reply this weekend. Quick note – the garage issue is separate from the house one. Unfortunately, the garage moisture problem is not easily solvable. Heavy metal stays cold when we have a warm spell. The warm air holds lots of moisture and that will condense on the tooling leading to the rust. The only way to avoid it is to heat the garage. I’ve just been resigned to wiping down and oiling my table saw and other heavy metal tools when this happens.

      • Rick – part 2 of my answer relates to your house getting humid after improving insulation etc.
        During the winter, in leaky homes where outside air easily mixes with indoor air, the house will typically be very dry in the winter because the cold outside air holds very little moisture. Because of this, people often use humidifiers to dump moisture into their air in order to prevent chapped lips, dry mouths etc.
        When you properly air seal and insulate a home, the air indoors holds in the moisture generated in the house from showers, cooking, breathing, plants etc. Many people have whole-house humidifiers attached to their furnaces, and those can create horrible moisture problems in homes that have been air sealed. In fact, in a properly air sealed home, excess humidity is far more of a problem than is dry air, so energy professionals almost always dictate turning off humidifiers and keeping a check on indoor humidity.
        In your situation, I strongly recommend buying a couple of inexpensive (~$20) humidity monitors and placing one on each floor or large area of your home. During the winter, indoor humidity should be maintained somewhere between 25%-50%. If you find it going above that, then there’s very likely sources of moisture that are causing the humidity levels to increase. Track those down and control the humidity and the problems you’re experiencing will most likely disappear.
        If you cannot reduce the humidity in spite of trying to keep humidity down, you can force some fresh air flow into the house by keeping one bath fan running full time. This will keep a small air flow of fresh air (the air blown out of the house by the fan is replaced by air sucked in through cracks, windows, etc.). You’ll find the indoor air quality improves considerably during the winter when the house might be sealed up for months at a time. It will also keep humidity levels down by bringing in the dry outdoor air. Again, you want to monitor indoor humidity levels to keep them in the comfort zone listed above.
        One other thing to keep in mind is to be careful opening the house up when it’s very humid outside. During warm spells like our region had recently, the air is saturated with moisture. We all want to flush out the stale air in the house so we open windows and let the fresh air in. But along with the fresh air can be gallons of moisture. Again, monitoring indoor humidity is key. If the humidity gets too high, a dehumidifier may be called for.
        I hope this gives you some clues as to what might be happening in your home. If you have any other specific details you want to add, feel free to drop another note.

  11. Ted,
    I have a bit of an odd question that you may or may not have an opinion on. I have a standard bathroom (5×10) with a vent fan and 3×3 operable window. I’m going to be applying a pvc beadboard to the ceiling. They are individual planks that are 1/2″ thick by 5″ wide, tongue and groove. The ceiling is currently painted with a semi-gloss latex paint. My question is do you think I can apply the planks directly to the ceiling, or should I install 1x nailers to the ceiling and then the planks to that to create an airspace between the drywall ceiling and the beadboard? With the planks fitting together with a tongue and groove, it’s not an airtight seal and my concern is moisture migrating through the tongue and groove and becoming trapped between the ceiling and planks if they’re nailed right to the ceiling. I thought maybe an airspace would help alleviate that. Or I suppose I could caulk or silicone the tongue and groove when installing, but that seems messy.
    Any thoughts?
    Much thanks in advance,

    • Good question. I like your logic – given the extreme moisture conditions, you certainly want to avoid trapping water between the beadboard and the current ceiling. Even with an air-gap, you might run the risk of trapping liquid water. Since shower air is super-saturated with water, it condenses even without cold surfaces. I’d be afraid of the moisture working its way through the cracks and condensing in the space.
      How about solution that doesn’t care if it gets wet? Maybe put something like 1/2″ foil face poly-iso on the existing ceiling. Tape the seams and caulk the edges so it’s definitely water-tight. Then apply the beadboard directly on top of that. Now the moisture can condense on the inner or outer surface of the plastic beadboard, or on the inner surface of the foil face, and it will ultimately just drip out, doing no harm.
      How’s that sound?

      • I had not thought of that, that’s a great idea! That’s why I come to you! What are your thoughts on insetting nailers of either 1/2” or 3/4” (the same thickness of the polyiso), caulking or spray foaming the she’s where it meets the wall or nailer, and then foil taping over the nailer and adjacent polyiso? So it’d essentially be air tight but with embedded nailers. Just thinking about getting nailers closer to the surface instead of trying to hit trusses 2’ on center through the foam.

      • I would think that would work as long as you protect the nailers. The foil tape will work as long as you overlap the tape enough for good adhesion to itself since it won’t stick to the nailer. I’d think 1/2″ overlap, at least.

  12. I have a mold test done in my home and need some help understanding the results. Would you be available to view the report and have a brief discussion about it. I would gladly pay for your time.

    • David, my specialty is more in determining what is causing the mold rather than in mold itself. Your best bet is to first discuss the tests with those who performed the tests and if that is not satisfactory, contact an “indoor air quality” specialist who has specific training in mold and mold remediation.

  13. Hi Ted, This sentence from this article describes my situation: “After deciding to tear off all the ceiling sheetrock, they found that almost all of the plywood roof sheathing was moldy,” except the mold in my case was discovered when I had the fiberglass insulation replaced in a small closet area. The mold on the sheathing was extensive, as far as the eye could see, and looks like it’s been going on for a while, presumably because of lack of adequate air flow though there has also been a leak around the chimney that goes through the closet area. I don’t know if all of the sheathing is in a similar state or if the ceiling dry wall is also moldy. What can be done in such a case?

    • I forgot to say I have cathedral ceilings throughout the house. The original owner said they “really packed the insulation in.” 😦

    • Hopefully, the chimney leak is responsible for the mold that you’re seeing in the closet area and the rest is clean. However, it would be wise to do inspections at other areas around the ceiling.
      Drywall is easy to cut and repair, though, of course, it requires re-painting, which is a pain.
      However, a professional can test for moisture in the drywall and roof sheathing with minimal disturbance. The moisture meters that I used to use included one that didn’t require any cutting – you just slid it along the drywall and it was able to report moisture levels. This is the first test that I’d have done. However, these moisture meters are fooled by metal so you really need to have a second type of meter that has pins that stick into the drywall and measure moisture directly. It’s still very low impact (no cutting or drilling, just a couple pin-pricks) so testing can be done without much visible damage to the ceiling.
      In order to measure the roof sheathing, which I’d recommend based on your assessment, you’d need to go on level beyond this and get someone with a moisture meter that has long probes. These require drilling a couple of small holes (1/4″) in the ceiling. The probes stick through those holes and reach up to the insulation and roof sheathing to measure moisture. It’s likely that the roof cavity is so deep that the probes won’t be able to reach, in which case you’ll actually have to cut out small sections of drywall.
      These types of tests will let you assess the extent of the moisture in your ceiling and plan your next steps.
      The first real question is: “if there’s moisture problems other than the chimney leak, where’s the moisture coming from?”
      Do you have recessed lights or other “holes” in the ceiling that would allow air/moisture to get into the ceiling? Without that, even with roofs packed with insulation, you usually won’t encounter moisture issues except in extreme climates. If you do have recessed lights cut into the ceilings, then those are almost certainly the culprits, so I’d test for moisture problems directly above the lights. It’s possible that there’s minor problems there (slight mold or darkening of the wood) that you wouldn’t have to worry about but replacing the recessed lights with air-tight, flush mount LED fixtures is highly recommended in order to reduce the risk of more extensive future damage.
      It can be hard to find a professional good at troubleshooting these types of issues. Almost no building contractors have the equipment so you need to rely on a specialist in moisture issues. You’d have to find out if they have the various types of moisture measuring equipment. If they have the types I’ve described, they’re likely serious. There’s three types I’d ask about: 1) “non-destructive” meter; 2) ‘pin-type’ moisture meter; and 3) long-probe moisture meter. These are illustrated at this website:

      I would strongly advise against trusting a general contractor for this work. That’s like asking your GP doctor to handle your lung cancer. You need a qualified specialist.

      • Thank you so much for this direction. If the sheathing is determined to be moldy and damaged throughout, what would be the course of action? TBD if the ceiling drywall is also moldy but if so, I’m wondering if ceilings and roof would all need replacement. A terrible thought! And a hypothetical question at this point.

      • Yes, worst case scenario is truly worst case – full re-roof, new insulation, new drywall. However, that’s only if they’re no longer structurally sound. Actually, worst, worst case scenario, the rafters have gotten rotten and are no longer structurally sound. But I’ve not experience that, so the worry of that is minimal. Rotten roof sheathing is fairly common, so I would see that as a definite possibility.
        If it’s just moldy but still structurally sound, typically people do NOT rip it out. You can paint over it and seal the mold in. The combination of that and the enclosed nature of the ceiling cavity locks the mold away where it’s not going to become airborne. As long as the moisture problem has been dealt with, the surface mold isn’t reason for concern.
        Disclaimer – if you have any sensitivities or concern about mold, definitely have an indoor air quality specialist test the air to ensure there isn’t an airborne mold problem. I certainly don’t want to be cavalier about mold sensitivities!

  14. Hey Ted, I’m hoping you can help me out. I live in Massachusetts and own a two family property that had a new roof put on last spring. Recently with the cold weather the attic has had some moisture issues that seem to be from condensation. The only area with a problem up there is a section of the attic that is directly above an open second floor porch. I added R32 insulation to the floor in that area above the porch but I didn’t add any on the gable wall next to it but I was told that would help.
    The roofer, as i see it needlessly put a ridge vent on the house when it has gable vents on both ends of the attic and no soffit venting whatsoever. I covered the gable vents for now but i feel if i blocked up the ridge vent and went back to the gable system it’s used since 1900 it would be ok. Do you agree and do you think insulating the gable walls will also help? The attic does need to be re-insulated but it’s only this one corner at this time that’s become an issue.
    If the ridge vent were to be blocked off what would be the best way to do so?
    I think the house has survived for so many years with the tables and the roofer just put a ridge vent up there not understanding about how an attic operates.
    Any advice is a huge help, thank you.

    • Hi Paul, thanks for writing.
      Let’s go back to basics for a moment. During the winter, the most likely source of moisture for condensation in the attic is from inside the house, escaping up into the attic. It then condenses on the nearest coldest surfaces. The only time you might get condensation otherwise is after a warm spell, when the attic is colder than the outside temperatures.
      I’m assuming that this is a “cold” attic, not an insulated section of the house since you mention venting.
      For a vented attic, insulating any area of the attic that is not directly adjacent to a heated section of the house (i.e. the attic floor above heated rooms) is unlikely to help anything. The main thing you want to do is figure out how the moisture is getting into the attic from the house.
      Is the area where you see condensation facing north? That is, is it a section that doesn’t get any direct sunlight? That’s usually where problems start since those are the coldest roofs.
      Besides the porch, what is near that area underneath? Any bathrooms nearby or other sources of moisture? Bath fans venting into the attic? Do you see any “holes” in the attic floor near the condensation that might lead into the walls of the house? Often the walls carry moisture from the basement or bathrooms, up into the attic.
      It is possible that the ridge vent without soffits caused the problem. When you have mismatched venting, the air going out the ridge has to be replaced from somewhere, so it can “suck” air/moisture from inside the house into the attic. With balanced venting (i.e. equal air coming in and leaving, there is no negative pressure (i.e. sucking) in the attic, so air from the house is less likely to enter. That’s a reason attic fans are “frowned upon” by the building science crowd – they create a strong negative pressure in the attic that can suck a lot of heated/cooled air from the house up into the attic, actually raising you utility bills!
      So step 1 is to look for any source of moisture from the house up into the attic.

  15. I have a sick house which is making me extremely ill. I’m not sure if it’s the attic or basement; probably both. A septic tank (no longer in use is near basement, when it rains does this fill and cause gas to enter the home, (over 100 years old). I’m sure the walls have old rotten insulation, probably just newspaper and the attic has had critters of all kinds through over a century of use. I’m a woman, 74 yrs and my husband can’t do much of the required labor. We are in lower Michigan near Ohio. Winters are bitter and lately we’ve had more than normal rain and its very damp. Summer’s can get to 85-90. This sick syndrome is not continual. Happens usually in the spring. Rest of the year it is fine. Does this problems ring any bells? I’m at a loss at what to do or where to start. I’m in a motel as it is so severe I cannot stay in my own home. Thank you.

    • I think my best advice at this point would be to look for an “indoor air quality” expert who can measure the air and assess what pollutants are in your home. That will allow you to focus your time/money on the areas which are most serious.
      I wish I could give you more advice, but what you describe sounds serious and is in need of an on-site inspection.

  16. Hi Ted,

    I really enjoy reading your blog and have a question(s) for you.

    We just had a house built a few months ago and we keep getting dust from the outside, inside our house everywhere. The down stairs is worse than the upstairs, as we have 2 separate heat pump systems. The area surrounding our home was excavated and we’ve had all that dirt mud/red clay surrounding our house, making the environment dusty as it was, but the house is 100% sealed, or we think it is. No open doors, windows, etc and dust is everywhere. The HVAC contractor never put a filter in the downstairs system’s air intake, so the system was running for a good month before we even noticed it, sucking in dust. We called the HVAC company and they told us that they put in a filter and that someone must have removed it. I guess we had a visit from “Casper The Friendly Ghost”, as no one removed anything. Their solution was to charge me $1,100 to come out and clean the duct system, which was complete garbage. I called 2 other HVAC companies and told them the situation and they both told me that they doubt a brand new HVAC system would have collected that much dust in a month, to warrant the duct system to be cleaned. We had on of them come out and they cleaned the coils and look everything over, as well as check the duct system, and they said that it did not appear that the duct system need to be cleaned. They said that it was probably from the dry dirt surrounding the house. That still didn’t answer my question of how it was getting into the house if everything has been properly sealed. We have 2 dogs that track in mud and dirt, and we also get it on our shoes from time to time, but not enough to cover the surface of everything with dust constantly. You can clean the whole house and within a day, it’s completely dusty again. The HVAC grills and filters get very dirty, very quickly. We recently had the yard seeded and sown and now have grass in most parts with some straw on the other parts that have not fully came in all the way yet. I figured this might fix our dust issue, but it has not. We are still getting in a bunch of dust. We’ve installed Honey Well Return Grille Air Filters that are 2″ thick and have a MERV rating of 11 to see if it would help, and it seems as if it has not. I’m not sure where to go from here and could really use some advise. We live in East TN, near Knoxville and would like to know if there are any professionals in the area that could come check out our situation. Any help, ideas, advice, input, etc would be greatly appreciated.

    Thank you,


    • Hey Ray, thanks for writing,
      You’re smart to be persisting with the HVAC people. I can’t believe the one company wanted to charge you a grand to fix their problem! Hopefully, you’ll never have to deal with them again – sounds like a con-artist 😦
      You hit the nail on the head when you wrote: “That still didn’t answer my question of how it was getting into the house if everything has been properly sealed. ” – Exactly!
      So the question is, where the heck is the dust coming in from?
      You’ve done great troubleshooting, especially with the return air filter. What that tells me is that the system is sucking air in from somewhere between the return air grill and the air handler – i.e. the return duct has an opening to somewhere extremely dusty.

      Here’s a possibility – some builders use wall and/or floor cavities as ducts. It’s extremely shoddy practice because it can lead to really dusty homes since it’s not a properly sealed system. It’s also inefficient. You can ask the installer if they did this. Of course, they might just lie and say “of course not”, in which case you would be within your rights to ask for that in writing. Then, you can check it out yourself by pulling off the return air grills and shining a light down the walls to see if there’s actually ducts in there. I usually find this situation on wall mounted returns but many floor returns do this too. You might have to use a mirror to peer down the wall cavity (or floor cavity) and you can also feel it with you hand by sticking your arm in there. Just be extremely careful of sharp edges on ducts which can be like razors. I know from experience…

      Unfortunately, if they did do the returns this way, the practical solution is to cut out the sheetrock and install real, sealed ducts wherever it’s missing. Obviously, this is undesirable, but frankly, it’s a heck of a lot better than dealing with an extremely dirty house for the rest of your ownership. Plus, it’s not really healthy. Mice love these areas and are prone to leaving all sorts of nasty things in there…

      Good luck. Please let me know what you find.

      • Thanks for your reply Ted. I believe that there are actual ducts in these areas of the house, but I’m going to contact a company called Prudent Energy Systems in Knoxville and see if I can get the to come out and do a dust blaster test on our systems, to see if we have any leaks, and to check for any other problems in general. I’m currently overseas and my wife really isn’t sure what she’s looking at when it comes to these type of things. I’ll keep you posted.

        Thanks again,


      • Great! A duct blaster test is exactly the right approach to take. The system has got to be sucking in that dust from somewhere.
        If they have a thermal camera, those can be extremely handy in quickly finding big leaks in the supply ductwork as you’ll get hot spots showing up. Harder to find on the return side.
        The supply ducts can suck in dust, even though that’s counter-intuitive. So the search will have to be thorough. But the duct blaster should give you good info.
        If they don’t find leaks in the ducts, I’ll be scratching my head!

    • it depends on how bad the roof is. obviously if it’s so bad that it’s leaking, then it will adversely affect your home’s Energy Efficiency. on the other hand if the roof is still basically sound then the heat loss will almost entirely the due to how well are sealed and insulated the attic space is.

  17. Ted,
    Not sure if this is your area of expertise, but you haven’t let me down yet, so I thought I’d give it a shot. Just had an old concrete porch removed from the front of my house and it exposed some previously covered foundation. The crawlspace is entirely encapsulated with rigid foam and air-sealed, so the only exposed foundation is on the outside side. The basement will eventually get the same treatment (rigid foam on the walls and air-sealed). What is your opinion on painting exposed foundations? The previous owners had already painted mine. Foundations are mostly in the ground so they’re always damp and absorbing moisture. I had always thought that the portion that is above ground is the only opportunity for any moisture in the foundation to escape. If someone were to paint it would they be locking it in and doing potential damage to the concrete? Or potentially forcing that moisture up through the foundation plate and rim joist and maybe even into the wall assembly?
    Thanks in advance!!

    • well, that is a different question for me.
      you’re right, it is out of my realm of expertise, but maybe we can think this one through.
      I do know that’s often exteriors of foundations are coated with a waterproofing sealant, so painting it should be little different as far as the effect on moisture. since it is sitting in moist dirt, just like a normal foundation it will always be wet. The thing is now that it’s exposed it will be potentially subject to freeze thaw cycles which could lead to cracking. but I would imagine this would be the case regardless of whether it was water sealed or not.
      so I guess my real answer is “I don’t know” 🙂

  18. I recently purchased a 1-1/2 story Cape-style house that was built in 1959 and is in need of some updates. A previous owner updated the house in the mid-80’s and I’m currently in the process of undoing their work.

    When removing the interior wall coverings, I discovered there is no insulation in the exterior walls and I’m wondering if I should add insulation or leave well enough alone and button everything back up with new drywall.

    Prior to the original siding installation, the exterior of the house was horizontally “wrapped” in 6″-10″ boards and some of them have 1/4″-1/2″ gaps that have allowed pests to penetrate through the years. At a minimum, I would like to make the interior of the home less accessible to creepy crawlers.

    I have a game plan, but I do not want to DIY myself into a situation that will require a professional to fix down the road. I’m seeking advice before I make an expensive mistake.

    Is following method logical for this scenario?:

    1 – Seal the 1/4″-1/2″ gaps with a closed cell canned foam such as Great Stuff.
    2 – Install an encapsulated fiberglass insulation without a vapor retarder such as Johns Manville ComfortTherm R13.
    3 – Install a 4-6 mil barrier across the face of the studs.
    4 – Install and finish new drywall.

    Note: The house is located in a woody area in central West Virginia. The summers can be humid and the winters can be frigid. The house is located on the border of climate zones 4A and 5A. Climate zone 4A is the official classification, but the next county over is 5A.

    • If the walls are standard construction, framed out with drywall on the inside and the boards you mention working as exterior sheathing, then that looks like a sound approach. If you want it tighter and even better insulated, since it sounds like you’re ripping out the drywall anyway, you might consider adding a layer of faced polyiso sheet foam, maybe 1/2″ thick, to the interior studs, then put up the drywall. You wouldn’t need the interior barrier then as the polyiso would act as a moisture barrier,. I’m thinking 1/2″ because that might be thin enough that you wouldn’t have to extend widow jambs much. However, it may turn out to be too much of a hassle if it changes the way they’re framed out. In which case, you could go as you mention.

      • Ted, I greatly appreciate your insight.

        Over the last few days, I’ve read some nightmare scenarios regarding insulating the walls of an older home and effectively creating a wet environment.

        At some point, probably when the home was updated in the mid-80’s, a previous owner installed vinyl siding. I’ve not yet determined if all the original wood siding is present under the vinyl, but a rear full-width porch was converted to finished space and wood paneling was installed over the original wood siding in that area. That particular area is now an interior wall, so my insulation of exterior walls will not effect this area.

        Given the above information, would the earlier method I mentioned still apply if I discover original wood siding remains under the vinyl?

        What if the wood siding was removed and the house was wrapped prior to the vinyl installation (unlikely, I know)? I assume my plans will need to change if this is the scenario, but I’m not sure of the extent of the change. Would I simply omit the 4-6mil barrier across the face of the studs if an exterior barrier was installed?

        …maybe I’m in over my head.

        I apologize for supplying so many scenarios.

        Guidance would be most appreciated!


      • The vinyl siding itself should cause any problems. It’s not air-tight so moisture should be able to drain out. I’d probably want a Tyvek or other barrier like that between the sheathing and the siding, but otherwise, that should be no problem.
        The interior moisture barrier should be fine also. These days, in most places, building scientists don’t see a need for this for the reasons you mention. This would allow any moisture that might get into the walls to dry to either the inside or outside, so you could save yourself the effort. Painted sheetrock is actually minimally moisture permeable. So just do your best to seal around outlets and other holes you make in the wall. Those types of things let hundreds of times more water into the wall than can pass through the sheetrock.

      • Ted,

        I’ve given this considerable thought and I’m positive new siding will be part of the plan a couple years out. I’m leaning heavily toward a Hardie product.

        For now, I think I’m going to modify the wall insulation plan (from the inside out) as follows:

        1 – Finished sheetrock
        2 – Omit the 4-5mil barrier
        3 – Encapsulated fiberglass without vapor retarder between the studs
        4 – Canned closed-cell spray foam in the cracks between the plank sheathing.

        When the time comes to install the new siding, I will specify everything should be removed down to the plank sheathing and the house should be wrapped prior to the installation of the Hardie product.

        Thanks again for your insight. This place is a wealth of information.

        Kind regards,

      • We did a Hardie siding for a while on our house. Durable and good looking.
        Good luck with your project! And thank you for your feedback. All the best.

  19. Hi Ted, I have two houses. One was built in 1967 and the other one 1972. Both have a gable roof, brick veneer with weep holes and are on a slab. #1 has gable end vents, soffit vents and 2 whirlybirds near the roof peak. #2 has soffit vents and a ridge vent but no gable vents. Both also have gas furnaces that draw combustion air from the attic. Both also have apx 12″ of blown in insulation in the attics.
    A foam contractor wants to completely seal the gable ends and roof decking with closed cell foam. I asked about the source for combustion air and he had a blank look then said no one ever asked that question before. I assume that a properly sized duct would need to be installed. I am also concerned that the wall space will not be vented any longer.
    Both houses are located 60 miles northwest of Houston,Texas. Thanks Rick

    • That doesn’t give you a lot of confidence in him, I’m sure! You definitely need combustion air but adding a vent defeats the purpose of the insulation. If the furnace is old, you might consider replacing it with a direct vent unit that draws combustion air through a duct to the outside.
      A sealed attic of this type is usually ok. Ventilation is usually used for either cooling or moisture control. The foam, if properly done,solves both problems.

      • Thanks Ted, that makes me feel more comfortable about the foam on the roof decking. I was hoping that I could retrofit the old furnace with a dampened duct if it was properly sized for the furnace and distance to the gable end. House #1 has a 29 year old Trane so it will be replaced next spring. I will be sure to get a ducted heater for that house. Rick

      • you can rig something up. Sometimes they do this for furnaces in homes. They run an appropriate sized duct to allow fresh air in. Then they put the outlet, facing down, into a container, like a trash can. This allows cool air to pool without just flowing into the living space. It’s supposed to be quite effective.

      • Thanks again from the quick response! I have searched all over for information and your site is top notch. I am learning a lot and will keep on reading.
        I will get with someone to size the duct for the furnace. House #2 has a fairly new system. A/C is the biggest deal in our area, I think I used my furnace about 2 weeks last winter. Thanks again, Rick.

  20. Hi Ted, Thank you for your article about mold. We just received a mold report on a house we are selling… would you be willing to look at it and let me know if it seems normal. Our relator said she has never seen one, but it looks very discouraging and extremely high levels. (?) Appreciate your time.

    • hi there, thanks for asking. I’m afraid I can’t do this type of work and your best bet is to stick with your mold specialist. you might be able to find a second company around there perhaps look for a company that specializes in indoor air quality rather than just mold in order to get a second opinion. this is especially important when buying and selling homes because mold has become such a big legal nightmare.
      just be wary of extreme reports from companies that do mold remediation because they charged thousands of dollars and operate on scare tactics. that’s why I like to use a company that doesn’t do the actual remediation work. since they have no vested interest in selling Youth Services they’re more likely to give you an honest answer.

  21. Ted, first off thank you for the post on l.e.d. inserts, I will opt for this solution.

    Are gaskets needed? None came with the Phillips airtight inserts I purchased. If so, I assume a window seal would do the trick?

    New question – the home energy audit also recommended more attic insulation. We are currently at R30 and would like to get to R50+.

    We currently have batting topped off with cellulose. Do you recommend more cellulose, or is it ok to add fiberglass on top of the existing insulation?

    Thank you again!

    • It’s definitely best to get circular cutout gaskets, though many are really cheap foam and don’t do much. What you could do that would provide an excellent seal, would be to use that gasket material that’s like clay rope. I’d take a couple strands, roll it together into one larger strand and make yourself a gasket. Then compress the LED insert to the ceiling. I’ve not done this myself since I had already sealed my fixtures from above, but in your situation, I think that could work quite well.
      As for insulation – blown in cellulose is a double edge sword. It’s great because it goes in quick, is pretty inexpensive, and fills in gaps. Batt insulation is much more labor intensive and prone to installation errors which can leave gaps.
      The flip side is that blown in insulation is not good if you need to use the attic for other things because it hides everything then clings to your pants, making a big mess when you come down from the attic. But if you never access the attic, it’s a great way to go.

  22. Ted, we recently had a home energy audit and found that we need to seal some recessed lights to prevent air flow into the attic.

    We have a contractor quote to seal from the top down, i.e. using a fireproof box installed from the attic. Option 2 is more d.i.y., to replace the recessed lights with an l.e.d. insert and gasket.

    I would prefer the l.e.d. insert option given it is much cheaper and prevents the contractor from crawling around in a tight space.

    Are there any pros or cons I should keep in mind for both options? Is the l.e.d. insert option going to be as air tight as the fireproof box?

    • Adam, thanks for asking – that’s a great question, I should write a feature article about this because it affects so many homes!

      I’ll start by saying that I have upgrades all of the recessed lights in my home with LED retrofits. This has numerous benefits over attic sealing. Prior to good LED retrofits being available, I had constructed airtight/fireproof boxes installed from the attic, so I can comment on both from first-hand experience.

      The retrofits were easy to do, taking maybe 10 minutes each, at most. These days, high quality retrofits are inexpensive, typically less than $30.

      – Totally air-tight when installed with a good gasket
      – Energy efficient – depending on your electric cost, the light will pay for itself, especially if it’s in a high-use location, like the kitchen. Usually less than a year.
      – Energy efficient part 2 – you can insulate the attic properly above the fixtures. LEDs generate much less heat than incandescents. Plus, you won’t lose the heat from air escaping through the housing.
      – Long lasting – quality LEDs are rated to last about 2-4 years running continuously. Compare this with an incandescent which has a life only one-tenth as long. This is much more convenient (less time on the ladder is safer too!). For most uses, that means you’ll never have to replace a bulb.
      – The light quality of “good” LEDs is very natural if you buy high CRI (color rendering index) fixtures. This is very personal, so compare the light from different fixtures to find one you really like. I brought home several, installed them and then my wife and I could see how they looked in our own homes which is much different than the display case in the store. You can usually return the ones you don’t like, so it’s worth trying a few.
      – The retrofit itself is quite simple usually. Most wire into your existing fixture using a screw in connector that replaces the existing bulb.

      Challenges with retrofitting from the attic:
      – Working in attics is not fun. It’s hot, dusty and access is often difficult. This makes contractors less likely to do a good job because they’ll be anxious to work quickly and get out of there.
      – It can be difficult to mount the air-tight enclosure in the attic given the construction of a typical recessed light fixture. This often leads to compromises that leave gaps, defeating the purpose of an air-tight enclosure.
      – Incandescent lights generate a lot of heat. Some older fixtures aren’t rated for enclosure. Usually this isn’t a problem however.
      – Covering the fixture with a housing can make insulation challenging. Most contractors are afraid of insulating around fixtures, leading to compromised insulation.

      Other considerations:
      – Some are dimmable – so make sure to buy the right type if you need them to dim.
      – The convenience factor of not having to replace bulbs in high ceilings is worth a lot.
      – Make sure the chosen fixture is the right size (4″, 5″ or 6″) for your retrofit. There are also different mounting styles that can affect compatibility.
      – Avoid off brands or those without a good warranty. The only trouble I’ve had with LED bulbs/retrofits are with cheap “knock-off” type. My favorites have been manufactured by CREE, which were the pioneers in LED lighting. Phillips also makes quality products.


  23. Hi Ted,
    It’s July in the Laurel Mountains in western PA. It’s been unseasonably warm and humid, high 80’s and up. My kitchen/dining room cathedral ceiling is a combination of tongue and groove and sheetrock. We have central air conditioning, most of the time we don’t need to use it. When the temperature is the highest around noon and the air has been on, I’ve noticed condensation and dripping from the area where the sheetrock joins the wood. Our roof is closed – no ridge or soffit vents, air conditioning vents are on the floor. From construction pictures that came with the house, it looks like the insulation is solid. The leak seems to be from the ridge and dripping down the slope. We had ceiling fan put in this past winter, it hangs from the boxed ridge. We’ve had a roofer check and there are no noticeable issues with the roof. After reading the comments above, I’m wondering if we need to open the boxed ridge and check if the electricians removed the solid insulation in the area of the fan? Other suggestions?
    Thanks, Deb

    • It is strange that the issue occurs under those circumstances. Normally, mid-day, the roof would be hot, leading to the least likely conditions for condensation.
      The location, where the sheetrock joins the wood is expected, since that seam is where the water could drip out. It’s also where the moisture from inside the house could rise up into the cavity.
      One possibility is that the wooden beam is cool enough (because of the air conditioning) that when the hot, humid air from outdoors comes in contact with it, it condenses, then drips down the beam and into your house.
      Did the dripping only start after the electrician added the fan?

      Another possibility – do you open the house up at night to get fresh air? Nighttime air is cooler and often saturated with moisture. That moisture could float up to the peak and condense on the cooler wood. I couldnt’ say for sure that is the cause, but it’s a possibility.
      If you do open the house up, I would discourage doing so on anything but low-humidity days. I’m always tempted to get fresh air too but usually regret it because of the amount of moisture that this lets in the house. Then I spend all day running the AC to remove the moisture.

      If the dripping continues in spite of being diligent to prevent excess moisture from entering the house, I would have someone carefully remove the ceiling along the wood beam so that the inside of the ceiling cavity can be inspected. If the wetting has occurred for a long time, it could lead to wood rot. You’d want to examine this and see exactly what is happening in there. Then formulate a strategy for “fixing” the problem. Without knowing the cause, I wouldn’t try to fix it by speculating about causes. That can lead to more problems and cost you $$$ and time.

      • It only occurs when we have the air conditioner running AND only during the hottest part of the day. We’ve only noticed it since the ceiling fan was installed. Thanks for your suggestions, I’ll have a contractor look at it.

      • That is truly odd! Based on your description, this is a longshot, but is there any chance that there’s an AC duct running up there? Often cold ductwork will lead to condensation. Highly unlikely given what you’ve described, but I wanted to rule out all known possibilities.

  24. Hi Ted,
    I recently purchased a home and have undertaken some substantial renovations. My home has a metal roof with a low pitch. It has soffits around the perimeter but no ridge or upper vents in the attic or anywhere else on the roofs. There has been a history of ice damming and there were some leaks which I have fixed.
    I am now thinking to spray foam insulate the attic area, but want to know if I should seal the soffits? The ice dams occurred at the lower portion of the eaves in a seam between 2 sections of 2 different roofs with ceiling heights being significantly different. One vaulted and one a more traditional height.
    If I close cell insulate the attic, but keep the same batts insulation in the other areas, will the other areas require vents to be installed? And do the soffits in the attic need to be sealed?
    I’m sorry if this is a little confusing- I have been researching a lot of different information and have also received a couple of different opinions.
    I’m thinking a combination of spray foam and venting may be required.
    Clarity and any help is greatly appreciated.

    • The ice dam issue is typically going to be due to heat leakage from the house around the perimeter. Due to the usually poor accessibility where the roof meets the wall, this area is often hard to seal. With proper blocking and vent chutes, they could spray in foam while protecting the soffit vents from being covered and allowing air to flow up the soffit and under the roof.
      For example, here’s a video showing how you could do this:

      Granted, since you’ll have the ceiling/attic floor in place, it won’t be this easy, but you get the concept. Once the baffles are in place, the foam will seal the air leaks and provide excellent R-value. If you choose, you could then use loose fill or batts elsewhere. But I’d recommend at least foaming a thin layer over the rest of the attic floor (i.e. ceiling of room below) to seal all air leaks, then add less expensive insulation elsewhere. But use a thick layer of foam out near the soffits, against the baffle, to avoid ice dams.

      Again, with the low pitch, access will be a bugger. But it’s worth a try.

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