Comments on: Spray Foam Insulation at the Edge – A Forensic Analysis

By: abailes

abailes — Tue, 27 Oct 2020 14:29:59 +0000

In reply to Donald Francis Bicknell. Donald, yes, that's true for

Donald, yes, that's true for vented attics and vented cathedral ceilings, but when you encapsulated an attic with spray foam insulation or install rigid insulation on top of the roof deck, you don't want the attic vented with soffit vents, gable vents, ridge vents, or anything else. It's a conditioned attic.

By: Donald Francis Bicknell

Donald Francis Bicknell — Tue, 27 Oct 2020 13:51:40 +0000

In reply to Scott Kilgour. You are supposed to have air
You are supposed to have air coming in through soffit

By: Jim Navotney

Jim Navotney — Tue, 22 Sep 2020 14:19:54 +0000

The off gassing of spray foam
The off gassing of spray foam can be very toxic and many have had to move out of their homes after using it so it is not for everybody.
And those that decide to foam their attic soon find they have moisture problems they never had before.
AIR is in fact the best and cheapest insulation which is why ventilated attics were invented.
And as always sealing a home airtight may save you a few pennies per day on your energy costs but at what cost to your health

By: Ryan Foster

Ryan Foster — Fri, 11 Sep 2020 15:36:23 +0000

Allison – We just bought a
Allison – We just bought a house built in 1919: slate roof, uninsulated walls, dirt crawlspace. Stucco siding and plaster walls. We’re pulling out the plaster walls to run new wiring and plumbing, so will be adding insulation. Guessing I won’t be able to afford spray foam for 100% perimeter, I was going to encapsulate the crawlspace with rigid foam board, air seal with spray foam, heavy liner. For the walls, thinking rockwool, and spray foam the underside of the roof to bring the attic into conditioned space. This post is super helpful regarding the eaves – so thanks for that! But I’m concerned about the 100 year slate roof and about applying spray foam directly to it. Closed or open? Ridid instead, and then air seal? We want to be in a spot where we can finish the attic, so the depth is definitely a consideration regarding ceiling height post drywall add. Thanks in advance!

By: Debbie Olmstead

Debbie Olmstead — Sat, 25 Apr 2020 18:12:53 +0000

I am up against a building
I am up against a building height restriction so energy truss height will be limited. I plan to use open cell spray foam to encapsulate the attic (low desert climate). Can closed cell foam be used above the plates since it has more R-value per inch, then switch to using open cell foam for the rest of the attic or will this cause some type of incompatibility in the attic (moisture or whatever)?

By: Bob G.

Bob G. — Sun, 19 Jan 2020 18:28:05 +0000

Looking at installing spray
Looking at installing spray foam to insulate / block air infiltration onto the roof sheathing in an attic in Colorado, so we can install HVAC equipment in the attic space. Should there be a concern in areas prone to forest fires with using spray foam which has an auto-ignition temperature below 700F (way below the heat of a fire)? Is there an effective way of installing less combustible products, like dense-packed cellulose?

By: Matt F

Matt F — Thu, 14 Nov 2019 20:27:56 +0000

In reply to Jeff. I used rockwool for block the
I used rockwool for block the eaves on my own house. 10/12 pitch roof and I placed the rockwool so you could see 4" of the 2x6 top plate. Do you see any issues with this approach if executed as described? The attic has a full unfinished floor with floor sheathing out to the band joist, so I cut the floor sheathing back about 16" all the entire way around. SPF was applied over down the roof and onto the top plate. Then they sprayed from the ceiling bellow, up to the underside of the floor sheathing/top plate to seal the band joist. There were some missed spots getting up to the top of band joist because it is difficult to get the gun pointed up there. A 20-24" opening would have been better. I realized later with an IR camera and box fans that I should have done a quick spray over the front of the top plate and bottoms of the rafters at the top plate.

By: abailes

abailes — Tue, 12 Nov 2019 12:30:00 +0000

In reply to John Meskimen. John, good question. No, an

John, good question. No, an encapsulated attic does not need to have the roof deck vented. The roof deck — and every other part of the house, too — has no need to breathe. First of all, that's a confusing term to use for buildings because it's used in different ways. Some people use it to refer to air movement; some use it for moisture. And it's possible you may be referring to the movement of heat to keep the roof cooler. So, no, an encapsulated attic doesn't need a vented roof deck. It's certainly possible to put one in, but roofs with spray foam insulation on the roof deck work fine without such venting.

By: John Meskimen

John Meskimen — Mon, 11 Nov 2019 23:13:54 +0000

In reply to Skye Dunning. I have a question/take
I have a question/take exception regarding your statement "The foam really needs to be sprayed from the roof deck, continuously, down to the top plate so if fully adheres to the surfaces and provides a continuous seal." Everything I have read states that insulation should NOT contact the roof deck so that air coming from the soffit vents can dry the underside of the roof deck, and you certainly do not want to seal the opening between the roof deck and the top plate or there would be no air flow. I understand you are insulating the top of the attic space at the roof, so it seems to me you need continuous baffles (like the common foam type) from the soffits to the attic ridge line to allow the underside of the roof deck to breath. Or are you not concerned about the roof deck breathing?

By: Ben

Ben — Sun, 10 Nov 2019 13:36:34 +0000

In reply to abailes. Recently had blower door test
Recently had blower door test on recently purchased 1989 house. 2150 cfm at 50 pascals. Should I include volume of unfinished basement in ACH calculations? The basement holds HVAC but doesn’t make serious attempt to condition for comfort, 2 registers and minimal fiberglass blanket insulation.