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SuperInsulated Sunroom (5): Outer Foam and Airsealing Tapes

September 12, 2016

Offset the joints and seal the gaps to keep air leaks out of the thick walls

Last time on Superinsulated Sunroom, we set the windows to be flush with the not-yet-installed outer layer of foam. The windows were sealed to the framing bucks along the sides. Above, a Z-flashing is formed to push any water out—if it ever gets behind the outer layer of foam, which is what we install in this episode.

Begin by ripping the panels to size and placing them on the wall. On the first layer, the full length panels were vertical, and they pieced in between with smaller pieces. On this layer the full length rips are installed horizontally—to offset the seams.

Because strapping will be screwed to the outside the foam, you only need two screws per panel to keep it from moving around. The screws are expensive, and wasting them where you do not need them can really add up.

With all the panels in place, the crew turns to sealing the seams in the foam‚ along the window bucks on the sides and top, and at the gaps between the foam panels.

Before adding insulation to the roof, they seal all the long gaps between the layers of the wall assembly. Zip System tape was added at the framing stage to seal the roof and wall sheathing. Calvin uses another flashing tape to seal the insulation to the Zip tape.

The tape is tenacious, so they keep it up off the Zip tape, and make sure to align the edges tightly before smoothing it down into place. Then, Calvin overlaps the rake strip shingle style. The outer edge of the flashing tape is then folded down to seal to the foil facing of the polyisocyanurate foam panels.

Finally, Zip tape is used to make a tight connection between the Zip sheathing and the air sealing tape that just installed. On the wall, Dave covers the seam with Dow Weathermate tape, which he is a big fan of "because it sticks to everything."

After the video was shot, the roof of this sunroom got two layers of foam, which were staggered and sealed the same way as the walls, then covered with plywood and roofed.

A super insulated sunroom may seem oxymoronic to energy nerds, but it is a tight addition to this energy independent home.

—Thanks to David Joyce, of Synergy Construction for opening his jobsite to our film crews. Thanks also to Calvin Cutts, PJ Burke, Damien Higgins, and John Albert for working with us and playing through the pain.

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