How to insulate the wall between cathedral ceiling and attic?

TractorGuy · Jul 21, 2020

My great room has what they called scissor trusses. They hung R12 bats on the wall and blew R30 on top. It still has a crawl space to get to the other end of the attic. Watch your head for roofing nails.

Dftodd · Jul 21, 2020

They installed standard wall insulation stapled to hold it in place on my house on the transition wall from a cathedral ceiling to standard ceiling.

KNPV PSD · Jul 26, 2020

Can’t hurt to get a quote on a professional to do a closed cell spray foam job. Those DIY kits are really expensive. A pro job costs under $1 per board foot here. The kit is just over that and you have to do the work....

kthompson · Jul 27, 2020

I have a son in law who is as tight a shopper as you will find. He sprayed his shop totally. Before I walked away from hiring it sprayed would at least get firm quote. It also helps seal.

WVBill · Jul 27, 2020

Build a 2X6 wall on the attic side of the truss and insulate it normally. easy peasy and you only loose 5 1/2" of attic space.

ovrszd · Jul 27, 2020

We added 2x4 studs to the "in" side of the trusses. Put Tyvek wrap on the attic side. Spray foamed the Tyvek for air transfer control. Bat insulated between the studs for R-Value.

Since you are as far along as you are, you would have to add the studs to the attic side of the truss as suggested above.

Understand this about Spray Foam. It has very little R-value. R 6-7 per inch. So you need to do something additional if you want more R value.

We sprayed 2" of foam (R value 12-14) and added 3.5" faced Batt insulation (R value 12) for a total R value of 24-26 and air tight.

defranks · Jul 27, 2020

Building an inner wall's a good idea, Bill. But the more I look at it, the more I think I'm just going to hire a pro. I've been working on this place for about a year, and I'm getting tired! I'm only a couple weeks from moving in, and I'd like to get that headache out of the way. The attic space is HOT right now, too. One insulation bid is $2100, or about twice what it would cost for the material to do it myself. It may well be worth spending $1000 extra to get it done.

I'll climb back up there and see how much a chore it would be to build the wall.

BTW, Bill, I grew up in Anacortes and spent plenty of time on Whidbey Island.

/pine · Jul 27, 2020

IMO building a wall or adding substantial framing just to insulate a surface is ludicrous and partially defeats the purpose...if the only reason is to add insulation...wood has a relatively poor R- value...
...As I stated before I would only add enough to hold up the insulation...just a minimal amount of furring strips (across the truss members etc.) is all that would be needed...

They make inexpensive plastic netting to hold insulation...even cheap chicken wire would be easier and cheaper than framing a wall etc...

The solution is KEEP IT SIMPLE...!