Comments on: How to Insulate a Short Attic Kneewall

By: Mark Bishton

Mark Bishton — Sun, 05 Dec 2021 21:35:33 +0000

I’ve been watching what happens to plastic in a hot attic over time for about 40 years. It isn’t pretty and the cheaper the plastic the faster it deteriorates.
I try to remember that the worst three words in construction are, “Nothin’ to it”

By: Hap Partridge

Hap Partridge — Sun, 05 Dec 2021 17:44:25 +0000

In reply to framistat. An easy fix we use- stuff a garbage bag with enough fiberglass tightly fill bypass hole, shove the bag in the hole (which conform to the hole) and blow cellulose over the top. Happy Home Insulation

By: Steve Scherer

Steve Scherer — Mon, 02 Aug 2021 19:36:01 +0000

In reply to Barry Edenbaum. My understanding is that fire stop blocking is required under Georgia code at any change of level, including knee walls.

By: Barry Edenbaum

Barry Edenbaum — Mon, 02 Aug 2021 17:18:26 +0000

The picture looking down into the wall cavity with no blocking at the ceiling level looks ominous from the standpoint of delaying fire spread. If it already isn’t, SHOULDN’T such blocking (aka a fire-block) be a requirement in such attic knee-wall construction ?

By: Gordon D McDowell

Gordon D McDowell — Sun, 01 Aug 2021 23:37:11 +0000

I worked for a wonderful design-build firm in south Louisiana for several years. We would sheath the knee walls with OSB and then 1/2″foam board, running both 12″ above the plate height to provide insulation dams for the upper ceiling areas. Have the carpenters do it BEFORE electrical, mechanical and plumbing, so those subs are cutting through our materials, instead of us working around them later. Wood blocking got installed at all ceiling lines. Then our insulation crew does the air sealing, just before blowing the knee wall cavities full of rockwool or cellulose insulation when they are insulating the rest of the walls. Just one of the many things we did to provide high-performing homes for our clients. Always gotta think like a drop of water or an air leak.

By: Allison Bailes

Allison Bailes — Sun, 01 Aug 2021 15:12:09 +0000

In reply to Cory. Cory and Benbo, the problem with just sheathing those empty cavities is that they're still not insulated. If the kneewalls are short enough, and the blown insulation outside is high enough to go over the top of the kneewalls, that would work. In this case, though, the blown insulation we added came up to only about half the height of those kneewalls. Without putting insulation in the cavities, that would have left the top half of those kneewalls uninsulated and subject to a lot of heat gain in summer and heat loss in winter.

By: Benbo

Benbo — Sun, 01 Aug 2021 14:04:04 +0000

In reply to Cory. That was my thought too. Why not just airseal it and be done?

By: Deniz Erkan

Deniz Erkan — Sat, 31 Jul 2021 04:04:05 +0000

In reply to Ron.

Haha I actually thought it was http://www.solexx.com and was about to try THAT material.

By: Paul Szymkiewicz

Paul Szymkiewicz — Fri, 30 Jul 2021 14:53:25 +0000

In reply to Ron.

Ron, take the motorbike. Ride into the sunset, and forget your building science worries.
Sorry, just couldn’t resist. Here is what popped up for me:

https://www.nofp.com/wp-content/uploads/2013/03/Reflective-Foil-Install-Guidelines.pdf

Don’t have time to study it now, at least I noticed they mention “system R-value” in their table. Previous conjurers of radiant barriers have made some wild statements about their R-value. It’s the “radiant” component. Goes out the window (or roof) when it touches another material, when it changes it’s behavior to conduction (on the side it touches).

By: Ron

Ron — Fri, 30 Jul 2021 13:34:27 +0000

In reply to Adam Stetten. Please provide a link for Solex. A Google search brings up a motorbike.