On this house we got lucky: It needed a new roof, so I had the rare opportunity to access some of the difficult attic air-sealing areas from the roof. It took 35 minutes to cover 70 linear feet of top plate.
Before we sealed with elastomeric, big wiring holes were stuffed with fiberglass to prevent material from flowing through them.
The attic had 59 light cans, 410 linear feet of top plates, 57 wire holes, six plastic pipes, three fan boxes, and two metal pipes—all punctures through the ceiling. Some of those punctures leak a lot and some a little, but the only way to kill the stack through the lid was to go after all the potential leaks.
With the spray gun, you don’t always have to be right up on the target. The spray rig could reach far back into the difficult juncture of rafter tails and ceiling joist.
This was a fairly simple and roomy attic to work in. There were, however, sections with belly-crawl access only, adding time to the job. Outside daytime temperatures hit 90 degrees, so we started early and quit early.
Sealing all the top plates and rake wall in the attic took about four to five minutes.
Wires need to be drenched in elastomeric, then pulled apart and wiggled so that liquid surrounds all the wires and sinks into the hole, thus sealing around each wire. We call this “puddle sealing.” This section took about two minutes.
Big holes are stuffed with cotton insulation to act as a gravity dam before application.
Once the big holes were stuffed, the 22 wires above a sub-panel took about a minute to seal.
This intersection of a rake wall, partition walls, and nailing plates took less than two minutes to seal. In complex geometrical areas like this, it is difficult to evaluate just where the leak is. Sometimes these areas are partially done at best, but more often, they are ignored completely.