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Old 12-05-2016, 03:54 PM   #1
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Insulating My Attic


First post here...Been on the forum a couple years mostly just reading...

I just bought my house which was built in 1984. The main portion of the walk-out attic floor is minimally insulated at best, but mostly uninsulated. The side-rooms that do not have attic access have blown in insulation. There are gable vents but not soffit vents. The heating/ac ductwork is routed through the attic space.

I was thinking of doing closed cell foam against the rafters/roof and turning the attic into conditioned space.

The other option would be to pull up the attic flooring and insulate, but I'd also want to re-insulate all the duct work.

Thoughts?

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Old 12-05-2016, 05:46 PM   #2
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Re: Insulating My Attic


If you are wanting to use the attic as more than just an outside space (i.e. humidity controlled storage), insulating the roof deck is the way to go. You can pull up selected boards if you are trying to preserve a certain percentage of storage and air seal and insulate surgically and add additional insulation between the storage planks and drywall.

Insulating the roof deck is absolutely a workable solution, but foam isn't cheap. Make no mistake about that.

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Old 12-05-2016, 06:03 PM   #3
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Re: Insulating My Attic


Thanks for the reply. I do plan on using the attic for storage. And I'm fortunate enough to be in a position where money spent and resale value of the home is really not too much of a concern.
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Old 12-24-2016, 10:00 PM   #4
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Re: Insulating My Attic


Sorry for the belated reply...

---------Welcome to the forum!---------------

That said, IMHO be aware there are precautions to take before simply spraying foam to the sheathing, reading the fine print, so to speak---strongly suggested; a fully adhered membrane under the shingles to stop water ingress. So if you have builders paper under them now (5-30 perms), you might want a less than 1 perm membrane installed instead to protect the sheathing... used to recommend foam in the test results. Or just SPF, kind of a coin toss....

Gary
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Old 12-24-2016, 10:14 PM   #5
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Re: Insulating My Attic


As far A spray foam insulation, I just removed an Ice Dam last year from a church that was only seven years old. They have a problem with the roof leaking only when snow was on it so they hired roof snow removal companies everytime they had a foot of snow or more.
Long story short the roof started leaking every time it rained after 7 years on a relatively new roof.
I gave an estimate to replace 10 square of shingle that was badly beat up from shoveling and assumed the shoveling must have punched hole in shingles.
When I stripped the roof I had never seen anything like it. The open cell spray foam had held water from a vapor trap from cold weather outside and rotted the seven year old plywood to nothing but black dust. We were literally walking on the spray foam as the plywood was gone.
The rafters were rotten so far down 3 inch nails would not hold the new sheeting. Open cell spray foam in cold climates can totally ruin the structure of your home. I have many pictures if you want to see. If you google it wou will see reports of crews not being able to walk on relatively new roofs becuase the sheeting is all rotten. If you do go with spray foam make sure you put the styrofoam after you install baffles directly against the underside of the plywood sheeting of the roof so no vapor barrier will form and so your roof can breath.

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Old 12-24-2016, 10:36 PM   #6
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Re: Insulating My Attic


This is just one of the photos I took. But the shingles and building is only 7 years old and the shingles just pulled up by hand here. The wood is totally gone, and the rafters were so rotten 3 inch nails wouldn't grab to hold the new plywood sheeting in spots.
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Old 12-26-2016, 07:14 PM   #7
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Re: Insulating My Attic


Wow, pretty nasty- and it appears to be real plywood, not OSB...

Code requires an interior vapor retarder with ocSPF or portion with impermeable foam; https://buildingscience.com/document...rchterm=attic+ Is that the 7# builders paper?

Thanks for sharing!

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Old 12-27-2016, 09:51 AM   #8
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Originally Posted by Gary in WA View Post
Wow, pretty nasty- and it appears to be real plywood, not OSB...

Code requires an interior vapor retarder with ocSPF or portion with impermeable foam; https://buildingscience.com/document...rchterm=attic+ Is that the 7# builders paper? Thanks for sharing!

Gary
The building was built to code. Connecticut is in the area as far north as you can get and still be allowed to use open cell spray foam. But my point is it was built to code passed inspection but especially for new products building code is always changing. Often times it changes becuase of observed problems and spray foam is still a very new product.

I have friends that have seen spray foam used in walls rot out studs on supporting walls. It's some scary stuff.
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Old 12-27-2016, 03:20 PM   #9
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Re: Insulating My Attic


Did the interior SPF have a vapor barrier spray applied per 2009 Code then?

"In climate zones 5 through 8, the “air impermeable insulation” must be a vapor retarder (Class II; 1.0 perm dry cup or less), or have a vapor retarder coating or covering in direct contact with the underside of the insulation. For instance, an air impermeable but vapor permeable spray foam (0.5 pounds/cubic foot) would not meet this requirement, unless a vapor retarder coating were applied (R806.4.4)."from; https://buildingscience.com/document...rchterm=attic+

Did you remove any ceiling drywall to check? Or was the foam thick enough not to warrant a vapor retarder?

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Old 12-27-2016, 03:37 PM   #10
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Did the interior SPF have a vapor barrier spray applied per 2009 Code then?

"In climate zones 5 through 8, the “air impermeable insulation” must be a vapor retarder (Class II; 1.0 perm dry cup or less), or have a vapor retarder coating or covering in direct contact with the underside of the insulation. For instance, an air impermeable but vapor permeable spray foam (0.5 pounds/cubic foot) would not meet this requirement, unless a vapor retarder coating were applied (R806.4.4)."from; https://buildingscience.com/document...rchterm=attic+

Did you remove any ceiling drywall to check? Or was the foam thick enough not to warrant a vapor retarder?

Gary
Connecticut is climate zone 4 and 5 not to mention the building was built in 2007 so it is before 2009 building code
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Old 12-27-2016, 03:43 PM   #11
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Re: Insulating My Attic


@Fred , One of the great misunderstanding (not you) is that codes, at best, represent the minimum quality a building should meet. There are many examples where the code people have compromised to "make it simple" that result in very poor advice. Saying a building was built to code requirements should carry a level rating, bare minimum, good, or above average. (probably better adjectives for that)

As for foam, they have turned a blind eye at related issues, IMO, because foam is an affordable high performance insulator. Your example was 7 years, very quick, but homes should last between 50 and 100 years. Many of the improved materials and methods put that in serious doubt. Again, my opinion.

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Old 12-27-2016, 04:58 PM   #12
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Someone mentioned just putting holes in attic walls and spraying foam inside the rafters. There is no way you could put a vapor barrier inside the wall this way. My experience with spray foam is to be very Cautious. If it is not done right it can create sever structural problems in house down the road.
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Old 12-29-2016, 09:54 PM   #13
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Re: Insulating My Attic


My point was; code doesn't require (open to others) a sticky low perm membrane on the roof side, under the shingles to stop water ingress there, as all the test results require that I've read... when using SPF in a cold/hot climate. I think the 2006 code did not require one either; hence my asking --- just building paper (5-30 perms) under the shingles?

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Old 12-29-2016, 10:51 PM   #14
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Quote:
Originally Posted by Gary in WA View Post
My point was; code doesn't require (open to others) a sticky low perm membrane on the roof side, under the shingles to stop water ingress there, as all the test results require that I've read... when using SPF in a cold/hot climate. I think the 2006 code did not require one either; hence my asking --- just building paper (5-30 perms) under the shingles?

Gary
There was synthetic paper underneath the shingles but no vapor barier inside the building. Just a dropped ceiling and a large gap to the rafters with open cell spray foam insulation. In a typical year no problems but in record cold years the water condenses inside the spray foam it looked like and would leak in building.
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Old 12-30-2016, 09:36 AM   #15
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Re: Insulating My Attic


A drop ceiling with OC SPF is a recipe for disaster in a cold climate.

The roof assembly isn't drying to outside regardless of the synthetic underlayment with any degree of sufficiency that would prevent this condensation and rot issue.

That roof was doomed from the start with the combination of a highly air permeable ceiling plane and OC SPF. If this were drywall, probably wouldn't have happened.

Even worse issue if they have ductwork above the drop ceiling.

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