Wall Top Air Sealing: Tips & Best Practices

[@Lughnerson]

First time I have heard about sealing the top plate, but it makes sense. Thanks!

[@Southern_Energy]

No problem, it's often forgotten but super important to a well sealed home!

[@seanmaxwell4976]

What I'm interested in is whether it's common for builders in moderate to warmer climates to use an interior air barrier product like INTELLO or some other interior wrap. There are many articles that say that most of the moisture management is accomplished by more airtight construction. Here in Australia they're already recommending interior wraps when we don't have good airtightness to begin with. Seems like we should focus on the simple and proven strategies like this video shows. Can't wait to see the next video.

[@Southern_Energy]

Sorry Sean for the delayed response, this one got missed in the comments! Glad to see you've been making some video's of your own! In my experience in the South Eastern US, interior air barrier are absolutely not necessary to achieve extreme air tightness if we get the framing and drywall details right. Air infiltration carries far more moisture than would be diffused through drywall or other vapor permeable wraps.

[@seanmaxwell4976]

I lIke it. Clear and well-scripted video. Good for builders of code-level homes. Can you tell me - do builders in the southern U.S. generally use an interior air barrier besides plasterboard? What was the target air leakage rate of this project?

[@Southern_Energy]

Drywall/gypsum is by far the most commonly used product for interior air barriers. Tply and OSB are often used for those secondary air barriers in chases etc. The majority of the houses we work in are code plus, the target on this particular house would be sub 4 ACH50. That's totally achievable when sealing drywall to top plates to stop infiltration from the attic.

[@micahmartin4762]

Very informative video. Building my current house. Drywall is already up - I probably would've used gasket foam had I known it exist. We just caulked the joint between the two top plates. Oh well. But thinking through it more, where exactly is the 1/8" gap at the top of drywall mentioned in the video coming from? If the drywall ceiling is hung first, then the wall drywall, then drywall tape/mud at that corner, where is the gap coming from? Where is the leakage? Is not the drywall the air barrier? Sincere question. Thank you. Lastly, anything I can do post drywall to air seal the top of wall to attic joint if that gap does exist?

[@Southern_Energy]

There is always some gap between the drywall and the top plate, which allows air leakage down from the attic behind the drywall (vertically) directly into the wall cavity. Then into the home through electrical outlets, switches, baseboards, etc. because those penetrations don't often get sealed on the interior walls. A dead giveaway would be air leakage around the outlets or fixtures on interior walls. Now the good news - If your attic insulation is not installed yet, you can still seal those gaps from above with a modest application of expanding foam. Any walltops, interior and exterior, that connect to the attic or unconditioned space should be sealed on both sides. Good luck!

[@micahmartin4762]

@@Southern_Energy Ah, I see. Attic insulation has not yet been installed, so we have a chance to seal those joints. Thanks for the response.

[@nfrost1986]

So I bought a thermal cam and have hot spots at the ceiling meets the wall could this be my solution and how do I do it if I already have drywall and ceiling

[@Southern_Energy]

I'd check your insulation levels in those areas first. Attic insulation (batts or blown) doesn't always extend over the wall top, leaving hot spots at the perimeter. Air sealing the wall tops with foam could also have some benefits, but it will be difficult to do from the attic side.

[@nfrost1986]

@@Southern_Energy so the insulation is pushed up against the wall top

[@danieloglesbdy2915]

I have recently heard that using foam sill seal on outside wall top plates have caused moisture issues there. Anybody know about this?

[@Southern_Energy]

We haven't seen any real life examples of sill seal causing moisture issues when properly installed on exterior top plates. More often we see damaged, missing, or poor, wall top air sealing cause issues here in NC. Condensation on walls and fixtures, excess infiltration, and high indoor RH to name a few. Sill seal can be very effective, but can also be easily damaged or removed during construction, leaving gaps. Regardless of the sealant material used there's a big reduction in the infiltration of unconditioned air behind the drywall, which carries a ton of moisture in with it.

[@noellynchard4158]

Dumb waste of time & money been framing for over 30 yrs

[@Southern_Energy]

hey everyone is entitled to their opinions and not every builder uses these techniques. But for high-performing homes and builders, wall top air sealing is a proven strategy to meet the standards they are building to.

[@tylerwright7422]

You're probably the type of carpenter who built the half-ass house I live in now and the reason I'm watching this video trying to figure out how to fix everything that's wrong with my house. If you think this is a dumb waste of time and money, you aren't building the same caliber house the video is referencing. 30 years of experience doesn't mean 30 years of wisdom.

[@Southern_Energy]

@@tylerwright7422 it's super frustrating when homes leak like you're experiencing. Thanks for tuning in, let us know if you find anything particularly helpful for existing home retrofits!

[@camcurry9687]

Framing and air sealing are 2 different things. When he needs help putting sticks together maybe he'll reach out to you.

[@andreycham4797]

You are right home buyers pay for sq footage or location . Nobody cares about performance of house