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Community and Q&A

Condensation on bedroom ceilings in winter

abrat2b | Posted in Energy Efficiency and Durability on

I live in Chicago. I have a masonry/frame 2 story house that’s 33 yrs old. I have R-25 fiberglass insulation in the attic, R-13 in the walls. I had my upper story exterior cedar siding replaced in 2011 with James Hardy board. The house was wrapped with Tyvek before installing the cement board. Ever since this was done, I’ve developed condensation above each soffit vent located above windows and also on one an exterior ceiling wall without a window, but does have a soffit vent above it, located on the north side of the house. This one is the worst and actually has water droplets on the ceiling the others get frost.

I know my windows being 33 yrs old and major air leaks was a portion of the cause, so I just replaced 16 double hung windows with new ones with better insulating value. They also foamed sprayed around the cavities so I’m hoping this makes for a air tight seal.

I was keeping my thermostat around 56-58 degrees during the winter in this upstairs portion of the house and the lower level at 64-66 degrees in the winter. Now I’m going to keep the upstairs at 62 all the time, in hopes that this will correct the problem of the condensation. I have a automatic humidifier on my gas furnace that I keep at a bare minimal setting.

I had a blow-door test done just recently, and yes there are many air leaks along the top plate and wall plates, but my overall reading was 1710. So on a scale of 1-10 my house is like a 7-8 and pretty tight. If I have all the air-sealing and more cellouse insulation blown into the attic to raise it to an R-49 for my region, like I wanted, I’m told I will now need a EVR installed to insure fresh air. I don’t want to install one and they are very expensive and no room in my basement to put in by the furnace.

I’ve been told in the past by my roofer, to run my power thermostat/humidistat fan 24/7 forever and this will help. Now I’m told by the energy auditor not to use it. Besides what I’ve read on your website.

I’m confused. but mostly I want the condensation to go away.

Please, do you have any advise I can take away and live without my ceilings being ruined or take a chance of mold developing in the attic?

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  1. GBA Editor
    Martin Holladay | | #1

    Someone needs to go up to your attic and improve the insulation thickness (R-value) of the ceiling near your soffits. The perimeter of your attic, where the rafters approach the top plates of your walls, has thin insulation. This is common.

    Ideally, your attic would have a full thickness of insulation (R-49) extending out to cover the top plates of your walls. In some houses, this is impossible, because the builders forgot to specify raised heel trusses, and there is insufficient room between the top plates of the walls and the underside of the roof sheathing to accommodate the needed insulation.

    The problem can usually be solved with a two-component spray foam kit. You want to install as much insulation as possible, with a relatively high R-value per inch, in this critical area. In most cases, you'll want to install wind-washing dams and ventilation baffles before this work is performed. For more information, see Site-Built Ventilation Baffles for Roofs.

    While you're at it, disable the humidifier. The humidifier is contributing to your problem. Unplug it, or turn off the valve that supplies water to the humidifier, or hit it with a baseball bat.

  2. Jon_R | | #2

    I'd also buy a humidity meter - keeping it low is critical.

  3. Expert Member
    Dana Dorsett | | #3

    If you are getting condensation on the ceiling in winter (to the point of dripping, no less!) you either have some missing insulation in that area or perhaps thermal-bypass path/channel drafting outdoor air from the soffits under the attic insulation.

    Active humidifidification would almost never be necessary in a house that tested at 1710 cfm / 50. A house that tight can usually be kept at a comfortable & healthy 30-35% RH @ 70F in winter simply by controlling the ventilation rate. Unless there are specific health problems that require higher relative humidity, hold the line at 35% RH, no higher during the coldest 8-10 weeks of winter. If it creeps up above that point, ventilate. A few $10 Accurite monitors distributed to a few place in the house make it pretty easy to tell if the humidity is creeping up.

  4. abrat2b | | #4

    Thanks for the great advise. Other questions come to mind from them.
    1. I assume that the spray foam sealing is with closed-cell polyurethane?
    2, By doing just the top plate area around the entire area will NOT cause a "tight-air" space leading to needing an ERV system since no other leaks will be filled (wall plates). I have many of the exposed conduit sealed already. but there are some leaks still.
    3. The baffles I currently have are the cheap black plastic ones from the home stores. Are these adequate or should they be replaces with foam ones? We are not in a position to install them ourselves, so would need a contractor to do.. Want to make sure I get the right ones.
    4. When the baffles are replaced, should they be spray foamed along the sides? I'm assuming yes.

  5. GBA Editor
    Martin Holladay | | #5

    Q. "I assume that the spray foam sealing is with closed-cell polyurethane?"

    A. Yes, that's what you want (because it has the highest R-value per inch). This isn't really a sealing job -- it's an insulation job. Two-component spray foam kits (available at lumberyards or home centers) cost about $300 to $600 each; that's the kind of kit you'll need if you do the work yourself. These two-component spray foam kits deliver closed-cell spray foam.

    Q. "By doing just the top plate area, around the entire area, will NOT cause a tight-air space leading to needing an ERV system since no other leaks will be filled (wall plates)?"

    A. Your question is confusing. The work I recommend (improving the R-value of the insulation above the ceiling) has nothing to do with sealing air leaks in your home's thermal envelope. (You do, however, want to limit the flow of exterior air between your ceiling and the insulation.) Doing the work I describe will not affect whether or not your home needs an ERV.

    Q. "I have many of the exposed conduits sealed already."

    A. I don't know what you mean by "exposed conduits."

    Q. "The baffles I currently have are the cheap black plastic ones from the home stores. Are these adequate or should they be replaced with foam ones?"

    A. In most cases, the black plastic ventilation baffles are sturdier than the foam ventilation baffles. If you are careful when installing the spray foam, your plastic ventilation baffles should be OK. If you are worried about the sturdiness of the baffles, you can, of course, replace them with sturdier commercial baffles or site-built baffles. For more information on this issue, see Site-Built Ventilation Baffles for Roofs.

    Q. "When the baffles are replaced, should they be spray foamed along the sides? I'm assuming yes."

    A. Yes, it's best if the baffles are installed in an airtight manner. Of course, if your insulation consists of spray polyurethane foam, this step is taken care of automatically when the spray foam is installed.

  6. abrat2b | | #6

    Thank you for all the great advise and helping me to better understand my problem and resolving it. My attic space is approx. 1040 sq/ft and something that I don't feel I could do justice in the application process. I will leave the baffles in place and make sure they are properly covered with the spray insulation.

    What I was referring to with the conduit was that my husband and I, about 25 years ago, went up and "Great Stuff" sprayed, a lot if not all, the openings where any holes penetrated the floor area. From the conduit for the electrical in the bedroom fans to the recess light cans where I made covers to go over them.

    In the basement I did the same thing with all the plumbing holes, duct work, etc Anything that made a hole got foam filled. Even under the kitchen sink area! I taped and sealed the duct trunk for any air leaks. My hot & cold pipes are also covered with pipe insulation If I couldn't spray behind outlets, especially the outer wall ones, I made my own insulating covers to go behind the trim plate (they didn't have them commercially at the time for the Decor style) and put plugs in the receptacles.

    I was way before my time when making sure I got as much drafting stopped as possible. I know I still have air leaks, but fixing the condensation is a higher priority. We had the house built 33 yrs. ago and it's been pretty much maintenance free. I want to keep it that way and ready for another family, in time, to enjoy.

    As I said, I truly appreciate every ones help and will now look for a contractor who will only do this and not push for adding more cellulose. I'm sure glad I found your website. It's been very enlightening. Thanks!!

  7. Expert Member
    Dana Dorsett | | #7

    R25 fiberglass is barely half current code minimum R49. Air sealing is always the first step, but adding more cellulose IS completely warranted, and a good idea.

    Don't rule out a contractor just because they recommend increasing the thickness of the insulation. Increasing the insulation is absolutely the right thing to do, just not the only thing. Using cellulose wherever you can is usually less than 1/5 the cost of closed cell foam for the equivalent R value, and it's much more environmentally friendly. Closed cell foam may be necessary to get close to R49 over the tops of the exterior walls due to the shorter distance to the roof deck, but cellulose is a better choice for the rest.

  8. abrat2b | | #8

    In regards to Dana's comment, Would it be more beneficial to do the cellulose insulation in the top plate area or the closed cell foam to get good coverage in that area to stop any future possibilities of condensation forming? Since cellulose is loose partials, then wouldn't it get into the tight areas anyway, like the foam?

    I'm not dismissing the rest of the attic being under today's R value recommendations, but at this point, it isn't my first priority. If cellulose can accomplish my needs at the top plate then I would consider doing the entire attic space w/o air-sealing, which I know you all will disagree with.

    I've lived here for 33 yrs and maybe have another 10 to go, I don't know. But to spend the money to do air sealing and have to add an ERV, I won't recoup that cost and the house doesn't have cold rooms or uncomfortable living conditions, IMO.

    If I was building again I would be all in for a perfectly tight air quality home, but at some point you have to ask yourself what is feasible and what is affordable when dealing with homes built before all the standards were in place and changing continuously. I can assure you that my home would not reap the financial benefit when selling to offset what it would cost me to achieve these standards. On a fixed income you have to weigh the options.

  9. GBA Editor
    Martin Holladay | | #9

    You wrote, "But to spend the money to do air sealing and have to add an ERV, I won't recoup that cost."

    No one is talking about air sealing or ERVs. Dana and I are advising you to improve the R-value of the insulation above your ceiling. This is not air sealing work; this is insulation work. It won't affect whether or not your house needs an ERV.

    The reason that closed-cell spray foam may be preferred near your eaves is that we are guessing, based on experience, that the vertical distance between the top plates of your exterior walls and the underside of the roof sheathing is less than the 17 inches or 18 inches you would need to insulate this area with cellulose. Under those circumstances -- about which Dana and I might be mistaken -- closed-cell spray foam is preferred to cellulose because it has a higher R-value per inch.

  10. Expert Member
    Dana Dorsett | | #10

    If you're looking for "payback" in under 10 years, don't do anything, paint over the moldy sections of ceiling that had the chronic condensation when it's time to sell the house.

    If you want the dripping ceiling to actually stop, you DO need to address the "...many air leaks along the top plate and wall plates..." as well as insulate over the top plates of the walls.

    Air sealing and insulation will pay back in marginally better comfort if not dollars. If your wintertime indoor air is so dry that you need to actively humidify to get it up to 30% relative humidity air sealing alone would fix that.

  11. Jon_R | | #11

    > Now I'm going to keep the upstairs at 62 all the time

    Warmer will help. As will completely disconnecting the humidifier. Adding attic cellulose is low cost and also reduces air movement.

    Idle speculation: if for some reason you can't get adequate insulation in the attic, perhaps you could add rigid foam to a portion of the interior side - similar to a tray ceiling.

  12. abrat2b | | #12

    Thank you for the clarification to my misconstrued thoughts. When I spoke to the company that did my blow-door test yesterday, they said in no way could they do the insulation UNLESS the air-sealing was done, cuz it wouldn't fix the problem. AND IF they did both procedures, they ethically couldn't do that unless I got an ERV. When I had another company come for an estimate after this test was done and showed him the numbers from the meter, he too said I would need one. That's why I'm so confused. Sorry. I want to understand, but as a laymen, it takes time to sink in :o)

    I took your advice and ordered 3 hydrometers, have turned off the power attic fan and will not turn on the humidifier on the furnace. And I'm assuming the ideal humidity level should be around 30-39%.

    Here are pictures of the audit report and the air leakage and attic Hopefully these will clear up any questions that I may have attributed to with the bits and pieces I've said in the past. The easy fixes of can lights, door hatch is something I can do. I just want to know that blowing insulation into the attic WILL FIX my problem without going to the extreme.

    My house has a 4/12 pitched roof that you probably can't tell from the picture.

    After reviewing the pictures, if you still believe it's feasible to just add the cellulose alone and it will stop the condensation issues, then I'm comfortable with that and will move forward.

    Thank you all for your patience with me. It truly has been a great learning experience.

  13. abrat2b | | #13

    Here is the blow-door results.

  14. GBA Editor
    Martin Holladay | | #14

    We're up to Comment #13, but my opinion hasn't changed. Go back to my Comment #1.

    This looks like a lousy job of insulation. The wrong material was used (fiberglass batts, which are air-permeable). Most of the rafter bays have no ventilation baffles, indicating sloppiness. The available height near the eaves looks insufficient for a good job.

    Back to square one (and my original advice). If you are getting condensation on your ceilings, you have to improve the insulation in this vulnerable area, using the methods I suggested in Comment #1.


  15. Expert Member
    Dana Dorsett | | #15

    This is the first I've heard of the powered attic fan! That could easily be a major contributor to the problem, since depressurizing the attic with a fan is a MUCH more powerful air-leakage drive than stack effect alone. (Or was that what you meant by "...thermostat/humidistat fan..."?)

    You may need mechanical ventilation even now- even air leaky houses need ventilation. The random air leak points in a house does not guarantee that the ventilation air is going to where it's needed or that it's provided via an uncontaminated path. Higher air leakage does not in any way ensure good air quality. It's somewhat orthogonal to your blower door leakage numbers, which is just a number- it tells you the approximate summed size of the total leak holes, but not your actual "natural" ventilation rate, or where the entrance & exit holes are. The ventilation also doens't have to be ERV, or HRV to meet code- even a continuous exhaust-only ventilation (which is pretty cheap) would do. But a pair of ductless Lunos e2 or Lunos Nexxt HRV vents (they work in pairs) should be comparatively easy to retrofit if it came to that, and should assuage the conscience of the air sealing & insulation contractor, even if it isn't capable of meeting the ASHRAE 62.2 ventilation rates (which are arguably much higher than necessary, and almost never met anyway.) Then you would at least know the source & path the ventilation air, unlike continuous exhaust-only approach.

  16. GBA Editor
    Martin Holladay | | #16

    Dana's right about the powered attic fan. It could be pulling in lots of cold exterior air at the soffit vents. That would certainly explain the cold ceilings where condensation is collecting.

    For more information on why you never, ever want a powered attic ventilator, see this article: Fans in the Attic: Do They Help or Do They Hurt?

    You may be the first homeowner to post on GBA with both a humidifier and a powered attic ventilator. Lucky for you, we're simplifying your life and lowering your energy bills by telling you which appliances need to be unplugged -- now.

    Disabling these two unnecessary (and harmful) appliances may be enough to entirely solve your condensation problem.

  17. abrat2b | | #17

    Thanks Martin and everyone for all your help. I have my 3 hydrometers in place now (after making sure they all read the same) In one upstairs bedroom the average 51-62% humidity while the temp avg is 59-62 degrees, the other bedroom is 50-60% & the temps are basically the same. Both bedrooms are on opposite sides of the house. This seems high to me. Upstairs thermostat is set at 62, lower level is set @ 64-66. The one on the lower level is 49-56% and temp 64-67 degrees. I know there are variances to consider, but do these seem to be in range? Our outdoor temps have been as low as 32 this morning to 68.

    The last question I have is, after looking at my picture of my attic, how should I space the baffles? Should I put one on each side of the soffit vent for a total of 3 each at every vent, or every other rafter? I want to make sure I do this right. The ones I'm looking at are plastic 48" tall.

    Thanks for your advise.

  18. charlie_sullivan | | #18

    Those humidities are high. 50% is the highest you'd ever want in the winter--better is 35 to 40%.

  19. Jon_R | | #19

    Right now, the outdoor dew point is 32F which suggests 34% when heated to 60F. Did you completely disable the humidifier? If so, any other ideas as to where your moisture is coming from?

  20. GBA Editor
    Martin Holladay | | #20

    Your indoor humidity level is still high. It's hard to know whether this is due to the fact that you have been deliberately humidifying your house for years, causing everything in your house to be saturated, or due to some other source of moisture. Here is a link to an article that talks about all of the factors that can contribute to high indoor moisture levels, and ways to address these problems: Preventing Water Entry Into a Home.

    Concerning your ventilation baffles: You need a ventilation baffle in every single rafter bay. Ideally, the ventilation space is as wide as the rafter bay (or almost as wide as the rafter bay, since you may need to include spacer sticks to establish the ventilation gap). You can either use a commercial product like SmartBaffle or AcuVent, or you can make site-built ventilation baffles. For a thorough discussion of your options, see Site-Built Ventilation Baffles for Roofs.

  21. exeric | | #21

    Pat needs to install baffles in all the rafter bays like Martin says, and she also needs to insulate much more heavily at the exact same place where they will go. It seems like the logical thing to do is include both things in one step. That can easily be done by installing at least three inch thick foam boards that have about a 1" gap between the roof sheathing and the foam. That can be done with 1" thick spacing sticks as has been mentioned. The foam board should go up in elevation at least to the equivalent the height of the insulation height needed per code in the area where she lives. I don't know what that would be. This would be equivalent to a cut and cobble method up to that height. Fill the rest of the attic floor with cellulose.

    A big big advantage of this method over the suggestion to use 2 part foam where the foam baffles will go is that you are no longer taking on the risk of poisoning your house by an improper mixture. It rarely happens but it DOES happen sometimes. Don't do it if you don't need to.

  22. abrat2b | | #22

    Well it's been a month now since this conversation started and I wanted to give you an update as to how things have been going. Since taking your advise and turning off the humidifier on the furnace and the power attic fan, the humidity level is staying at 40% with a temp set at 62 upstairs when outdoor temps have ranged from 4-19 degrees outside this past week. Plus my house feels so much warmer. Almost to warm! My bedroom ceilings don't show any signs of condensation and we do have a good deal of snow on the roof, so no signs of great heat loss. The 1st floor humidity is averaging between 30-34 with temp set at 66 degrees. I hope next spring to tackle the rest of your suggestions, but in the meantime, with the new windows and your GREAT advise, hopefully the rest of the winter will be as positive. Thanks to all of you for the tremendous help. Have a wonderful holiday.

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