Closed foam insulation, condensation problems

Discussion in 'Insulation and Radiant Barriers' started by MommaJ, Mar 25, 2019.

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  1. Mar 25, 2019 #1

    MommaJ

    MommaJ

    MommaJ

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    015.JPG 044.JPG 1918 home with third floor attic to be converted into living space. New roof put on, closed cell insulation installed. We started sheetrocking, but had to stop. The ceiling runs from the top down to the floor. Everything is an outside wall. We are having problems with condensation where the spaces were too small for the foam to reach. Areas where there are two rafters side by side (crack is less than 1/8") around the windows, also around the electrical boxes. What can be done about these areas? There are several. Would caulk work? What kind? Any spray foam tips that go into very very tight areas? What about plastic to cover the entire area? Should we try to stick in fiberglass? What about the electrical boxes and light fixtures that had drippy water? Any ideas about them? In the picture, you can see the long 2x4 that was put up for supporting roof. Condensing between the new and the old joist. You can also see the electrical box on the right, in the foam, near the plastic. Second picture shows the dormer with two electrical boxes and one of the three windows. 015.JPG 015.JPG 044.JPG
     
    Last edited by a moderator: Mar 26, 2019
  2. Mar 25, 2019 #2

    bud16415

    bud16415

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    i would try the great stuff foam in the can. The tip is pretty small and if i couldn't get it in the crack i would drill some holes right on the crack line so the nozzle would fit back in.

    What does the company that did the work suggest?
     
  3. Mar 25, 2019 #3

    MommaJ

    MommaJ

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    Cracks are too small for nozzles. These are space cracks not a crack in the foam. Please see pictures. It's between the two boards, (old and new) and behind the electrical boxes which are on outside walls. They had to be mounted before they would spray the foam. Trusses are 2 x 4, electrical boxes are flush, couldn't do it any other way.
     
  4. Mar 25, 2019 #4

    bud16415

    bud16415

    bud16415

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    We may have some experts here that will jump in and help with an answer.

    It has to be a common problem in the industry as many times two pieces of lumber are sandwiched together.

    Reason i asked what your foam installer offered as advice.
     
  5. Mar 25, 2019 #5

    Snoonyb

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    A sistered member should be tight and you can use screws to pull them together.

    There elec. casketing material, which are size specific for elec. boxes.

    Painters caulk is cheap and reliable.
     
  6. Mar 26, 2019 #6

    mabloodhound

    mabloodhound

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    I've used the caned spray foam in small cracks. I squeeze the tip together to flatten it out (with my teeth) so it fits in the crack. Works fine.
     
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  7. Mar 26, 2019 #7

    nealtw

    nealtw

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    2x4s with out a bridge block for cold to warm, 3 " deep electrical boxes in a 3 1/2" space, not much R value in there.
    The cold areas will not get fixed but once the drywall is up the warm moist air will not have direct contact with the coldest surface and may not occur as much. You are completely sealing this up are you paying attention to increased moisture in the house just from people and cooking and showers.
    You have changed the dynamics of the house.
     
  8. Mar 27, 2019 #8

    rokosz

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    Your house is 100yo (happy birthday!) That's a beautiful space -- and no hitting your head on collar ties. What's going on downstairs? Is the basement dry? modernized slab? dirt?? /windows/stone foundation?. All your living area windows new and tight? too much or too little ventilation in any combination between floors of varying tightness will all contribute to the froth in the attic. Think like a chimney. I wouldn't consider the MN climate humid, but you probably keep your windows closed 6-8 months of the year. Were you part of the recent heavy rains/did you have above average precip in the weeks prior to your noticing the condensate? If so, maybe this is the worse you can expect (this decade)

    All the moisture in your house rises with the heat and gets up there in the attic. The warmest air, holding the most moisture, finds its way to the coldest spots and bam! Nealtw's right about once the dw is up that will help.

    But you can still benefit from a thermal break. Perhaps before drywalling use insulation "tape" on the edges of the 2Xs. I seem to remember a company called Aerogel or some such. It doesn't have to be fancy. Its been years since I did it but I remember using an insulation from the blue or orange box that came in 6"(?) wide sheets and about 1/4" thick uncompressed. Rip it to size and install the drywall over it. Use SnoonyB's & MABloodhound's idea in tandem: caulk the cracks a bit, cover the boards (the boards themselves need a thermal break regardless of condensate) then drywall.

    For the e-boxes: You can try the hardware store foam draft outlet covers. Of course that doesn't cover the receptacles themselves -- are they "airtight"? The boxes don't get messed with too often once roughed. Here's my seat of the pants: use some non-expanding spray foam in the deep of the box behind the receptacles. Maybe release the recepts, spray and quickly reinstall the recept. First find out if the foam is conductable or a fire hazard(!!). Need to work on the box? the foam is easily removable. Barring the foam, that same outlet cover stuff in a solid sheet could be cut to fit the back of the box and placed there. or use the left over sheet material from the 2x covering. go two layers deep -- it compresses.

    personally I hate maintenance needing to be done every <period> passive or active. They're both time and energy sucks. Active is cleaning your gutters (where I am) twice a year. passive may be what you ultimately end up with in the attic: a dehumidifier. I appreciate the distilled water they produce.

    I'll be quiet now.
     
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