In this video, Michael shows how to use spray foam, fiberglass and foam board insulation to properly air seal a knee wall in an attic. Watch as he shows step by step instructions. Everything from measuring and cutting the insulation to the application inside the attic knee wall.

How to Insulate a Knee Wall and Air Seal Attic

Hi Michael here and this video I'm going to show you how to insulate a knee wall in an attic  and how to do it properly using foam board and spray foam insulation stay tuned.

So here we are and on the second floor this house and as you can see this is a the door to the attic these are the knee walls so what we're going to do is we're going to insulate the other side of this knee wall because right now there's no insulation we will show you what that looks like in a second okay now we're inside the attic part a knee wall and I measured it from the door facing to the the the third stud here and it's about 61 inches we're gonna do these three sections of insulation and put a piece of foam board over them to air seal them but before I do that I'm gonna go and spray some spray foam around all these penetrations here here in the floor and also around the back vacuum pipe over there so you want to try to create as much of an air seal as you can in these attics okay so we were just up in the attic and got her measurements for the knee wall now we're gonna start cutting the insulation up into the sections that we need to insulate the knee wall here we go This is an R 13 insulation that is faced this is called the facing this part always gets installed to the living space anytime you install insulation you wanna make sure you have it going to the living space I want to see how long this is the piece is almost eight feet so we're going to be able to cut three feet off because we are dealing with a 5-foot section.  So now we're gonna put some fiberglass in the a hole here there's the first one we use an R-13 any time we are working with 2x4's because that's about the most you can get in there. There's one and two alright now we gotta cut a little piece for this section here so we got about eight inches wide so we are going to take our insulation remember always put the paper the living space so now we got our insulation properly installed on the section Now I am going to get my foam board and we will put foam board over this be right back okay last piece of the puzzle is putting our piece of foam board over the fiberglass batt insulation if you are trying to air seal your knee walls make sure you check with your local utility companies there could be a rebate for these kind of projects and check with your accounting services and insulation projects and things like that might even qualify for a tax credit so here in Tennessee we actually have a power through Tennessee Valley Authority and they offer up to $250 rebate for any kind of insulation work done in an attic so make sure you check with the TVA eScore Energy Right Program so here we go okay now we're gonna set up our piece of foam board and install it to the wall and we are going to nail it and make sure we got it going all the way across to our stud let's get a couple of nails I use roofing nails just holds a little better just tap in their little bit...done.

About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.

6 Comments

  1. Drew on November 11, 2015 at 4:57 pm

    Thanks for providing the transcript. It’s much easier to follow sometimes than the video itself. Thanks for such great advice as well! Good work.

    • Michael Church on November 14, 2015 at 12:55 am

      Glad you like it Drew. I appreciate the feedback about the transcript.

  2. Hannah on February 16, 2016 at 7:34 pm

    I’m in the process of sealing my attic so this was really helpful! Thanks for sharing it.

  3. Patricia Anderson on March 9, 2016 at 2:46 pm

    That is awesome that you could potentially get a $250 rebate for any insulation work done in the attic. We are doing attic insulation this summer to get ready for winter and we’d really life it if we could get a rebate. Unfortunately we don’t live in Tennessee so we’ll have to check with our accounting services. Why do they give you a rebate for these projects sometimes?

    • Michael Church on May 10, 2016 at 5:23 pm

      Patricia, this depends on your utility company and federal tax credits. Please contact you local utility company for more information. Thanks.

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