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Old 03-23-2014, 05:30 PM   #1
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Attic Frost and proposed fix

I noticed a frost problem on my attic ceiling this winter. I read online that the common cause of this is warm air entering the attic via attic bypasses. I do have attic pull-down stairs that arenít currently insulated with a box cover. I also have two bathroom fans that are about 24 years old so Iím sure they are not IC rated so they are not covered with insulation. There is also one canister light that is just as old and not covered. My house is a modular so there is a marriage wall and it isnít sealed. My plan is to build an insulated cover for the attic stairs, replace both fans with new IC rated units so I can cover them with insulation, replace the canister light with a normal light, seal the marriage wall with spray foam and look for any other openings like AC cables that arenít sealed around and seal them with spray foam. I was also thinking of caulking any electrical box opening (holes). Does this sound like a good plan? Am I forgetting anything? One of the bathroom fans vents to the outside via the attic soffit instead of the roof, is that OK? Is it OK to use regular spray foam to seal around Romex cables that enter the attic? If so, any special type? Do you have any good ideas for the attic stair box?
I have attached some pictures. Thanks in advance for the help.
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Attic Frost and proposed fix-img_0110-2-.jpg   Attic Frost and proposed fix-img_0122-1-.jpg   Attic Frost and proposed fix-img_0126-1-.jpg   Attic Frost and proposed fix-img_0135-1-.jpg  


lp2842 is offline   Reply With Quote
Old 03-23-2014, 05:40 PM   #2
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That fan unit needs to be covered with insulation. Otherwise any heat from the space below will radiate off of the sheet metal.

If you are getting condensation in the attic. It has to be coming from someplace.

What is that pvc going to, that is next to the vent fan? Also having that flex hose does not help any. It should be as straight as possible and insulated to keep it from allowing the warm line to cause condensation in the attic.

You may have holes in that flex line, which is allowing the bath humidity to get up there.


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Old 03-23-2014, 06:03 PM   #3
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Sounds like you have a good plan. They sell kits for the stairs. This is one example.
Search for attic stair insulation or cover and you'll get loads of options.

The sofffit exhaust is OK unless your soffit has venting that goes back into the attic. If it does, the bath exhaust is going back into the attic.
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Old 03-23-2014, 06:08 PM   #4
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Venting it out the soffit is just sucking the warm moist air right back into the attic. Should be out the roof.
If the insulation is blocking the soffit vents it needs to be cut back.
You left out the very important info need by leaving off your location in your profile.
Just go to quick links to edit.
That fan does not need to be IC, just cover it.
If that last picture is of the party wall I'd cover it with 2" foam, then cover that with insulation.
There is no special foam that needs to be used around the wires.
Is there soffits and a ridge vent on the roof?
When posting in forums, letting us know your location will help others give better feedback/advice/solutions to your questions
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Old 04-07-2014, 10:24 AM   #5
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Thanks everyone for your responses.
Comments and/or answers to some questions:
> The attic fans are from 1990, so I don't think they are rated (IC) for contact with insulation. They are also getting kind of old and noisy, so I was thinking of replacing them with new (IC rated) fans, sealing around them with spray foam then totally covering them with insualtion.
> The PVC next to one of the fans is for a toilet vent stack. As part of my sealing plans I will check where the PVC enters the attic from below and seal around with spray foam (if it not done so already).
> I will change the flex pipe to the rigid type and also insulate around.
> I will also change the soffit end vent so it goes go through the roof instead.
> Yes, I have vented soffits and a ridge vent. Yes, I can see daylight coming in from the soffits when I look in the attic. It is still extremly hot up there though on summer days. I think everyone is in the same boat there though. I used to have an electric gable-end vent, but I was told that it could actually cause issues with air flow since I have a ridge vent. My gable ends are closed now sicne I had siding done, but i have a ridge vent and soffit vents.
> For the attic insulated box, I did look at some that are pre-made, but didn't really care for the quality. I was planning on making one out of 2" rigid insulation installed inside a cardbox box (if i kind find one of the size needed). I was thinking if putting it in a stiff box and gluing it with liquid nails just so it would be rigid. I thought about making a wood box with the rigid foam inside, but it would be heavy. (Any other ideas instead of a cardboard box?) I was was then going to use foam weather stripping around the edges and pull it down into place with bungy cords attached to bolts (with large washers) that go through the box. Question: I see they sell this reflective insulation ... would that be good to put on top of the box? I see some pre-made units have something similar. What purpose is it serving?
> Question: So it is ok to use Great Stuff around Romex in the attic where it goes into the walls below? If so, is any type is ok? It wont eat the plastic Romex cover will it?
> Question: Any fan make/model reccomendations that are IC rated? My current fans have a 13" opening in the ceiling sheetrock. They have two switches, one for fan on/off and one for fan light.
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