Air Sealing Details

Hi again,
Last week was another action packed week. The sheetrock hanging was finished today (friday) and 3/4 of the exterior siding was completed. For me it was an intense focus on the final air sealing details and finishing the boron spraying of all the interior walls and rafters before sheerock. Next week we plan to finish the siding, finish all the blow in cellulose and fire tape all the new sheetrock and finally do our blower door test for the completed interior shell.
Enjoy .... Terry

Any good morning starts out with tea. Here, Charles and I are sitting on bales of cellulose to be blown into roof and wall cavities.

Every penetration/ puncture in the envelope was sealed on both sides of each layer. Every hole was made slightly larger than the pipe to allow the flexible caulk to fill the gap, thus not relying on a tight wood- to- pipe seal that could open over time with expansion and contraction. The penetrations were also sealed on the exterior side of plywood where it meets the exterior foam and again where the foam meets the siding. so each pipe here gets sealed four times from interior to exterior. Here we see a plywood shroud around three punctures so the sheetrock can be set in a bed of caulk around the penetrations. Every puncture had at least a 1" wood backing/ bed for the sheetrock to seal onto.

The sheetrockers at first did not get the importance of air sealing the key connections. I had to watch every sheet going up until I was confident they understood every contact point had to be perfect and all their caulk lines had to continous and fat enough to fill the gap. Here Louis is calking the plywood shrouds and edges of the framing at floor and end of sheets.

As drawn by architect- yes that is an exterior roof jack on the inside of the room. The sheetmetal is caulked and sealed against the plywood- the rubber flange is the air seal.

This is a standard plastic switch box. I wanted to see if I could make it airtight with a flange in front in which to seal the sheetrock, mimicking the special ones we bought (below). The wire holes in the back of the box are packed with duct sealer putty.


Air tight electrical box blobbed with caulk and ready for sheetrock. These airtight electrical boxes are made in Minnesota where the cold weather demands higher standards for air sealing. Here you can see the wide flange in which to apply caulk to seal the sheetrock. Note: the run of caulk at bottom plate ready for sheetrock-that missing spot in the caulking was corrected).

The cellulose insulation will be blown in after the sheetrock is in place.

Squish out is what I like to see. Here you can see a good caulking seal between the sheetrock and 2x6 sill of the window.


1 1/2" holes were drilled in every rafter bay at end blocking.

Charles then blew in insulation into each cavity from the outside at 3.5 lbs per cubic feet- AKA dense pack. Each hole will be plugged and sealed. We decided to insulate all the walls this way rather than blow in wet cellulose into open cavities or blow in dry cellulose behind netting before sheetrock. Wet pumped cellulose would require a long period of drying time before sheetrock could be done and we did not want to wait or run dehumidifiers for a week to dry out the cellulose.