Dan Morrison | April 07, 2016

YouTube // Glues, Sealants, Coatings, Framing, WRB & Flashing, Insulation & Air Sealing

Air Sealing Details for a Net Zero Energy Home


Gaskets, foam, and adhesive seal the gaps and cracks at foundation/mudsill connection and other common air leaks


In this video from zerohomes.org, Bill Hull, of WH Hull Companies, explains the air sealing process for a high performance home in Oregon—a house with double-stud walls. Bill focuses mostly on the floor to foundation connection, but moves inside to windows and doors also.

He begins by zeroing in on the foundation to framing connection, where gaskets, foam, and adhesive fill the gaps between stem wall, mud sill, subfloor, and wall plate. Anchor bolts are sealed with spray foam from the inside. Also, the wall sheathing spans this assembly to add a layer of redundancy.

 At the windows, he seals a 3/4-inch plywood box that spans the two stud walls to keep the opening airtight.

Matt Douglas, an energy consultant, explains that he verifies that all holes have been sealed before the insulation contractor comes to the jobsite. He points out an electrical box that has not been sealed and notes that there is a lot of air coming through that hole.

Exterior doors have a triple-point lock, which latches at the top, middle, and bottom. It provides a much better seal than a standard door lock.

The door is also sealed with weather stripping around the perimeter and an adjustable threshhold. Bill says that when they tested with a blower door, they found the glazing in the door to be leaky, so they fixed it.

Nice job, Bill and company.



I do not like the method of cutting the wall plate for the anchor bolts instead of drilling the holes near the same size as the anchor bolts. Also, if this is a net zero energy home then aren't the walls going to be insulated with spray foam? If they are then the anchor bolt, electrical box and other penetrations are going to be sealed with the spray foam. If the walls are being sprayed with foam then running electrical wiring through the studs should be considered a very dumb thing as it is a fire hazard if the foams contacts the wiring you are going to increase the temp rating of the wiring and creating a fire hazard. I have seen this happen on more than one occasion. It would be better to bring the wiring and boxes through the floor if spray foam insulation is used in the exterior walls and bring wire up through the interior non-insulated walls for lighting and controls..

Daniel Morrison's picture

Thanks for the comments Cliff,

Spray foam can be a great way to insulate a house and air seal in a single step, but it is a lot more expensive than other types of insulation, and it does not address thermal bridging at all.

Some builders use double-stud walls to overcome this, some use exterior insulation, such as rigid foam or rockwool, to break the thermal bridges. In temperate climates like much of California, the temperature differential from one side of the wall to the other does not warrant such extreme insulation strategies.

I don't know why the mud sills are notched for anchor bolts, rather than drilled (maybe a rookie got loose?), but either way, the hole has to be plugged with some low-expansion foam.

Our main reason for showing this video was because Bill does a great job of pointing out the many, many areas that air can leak in and the attention to detail necessary to keep it all tight.

If you have some airsealing, insulation, or any other construction tips, tricks, or tactical advice that you'd like to share with us, we have made it very easy to post articles, videos and slide shows to ProTradeCraft—please do!




For every owner, it is really essential to take care of their home, so in that case, they used to take the help of professionals to protect our home from different maintenance problems. This video footage also describes the importance of air sealing, especially after the installation of windows and doors or any other wooden materials, we have found some minor gap after years which allows the air to pass. Therefore, we require air sealing options for our home, as a home owner I would like to follow the video footage to get better instructions on this topic.

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