After allowing the tested caulks and sealants to cure for 48 hours, the author pulled the wires from side to side to simulate the effect of wiring a fixture or receptacle. Materials were judged to have failed if they pulled away from the cable sheathing, leaving a visible gap. The three-tiered rating system assigns a DNF (“did not fail”) rating to sealants that remained intact throughout testing; an NMF (“numerous movement failure”) to sealants that eventually lost their grip; and a QF (“quick fail”) to ones that failed immediately.

When it comes to air-sealing, canned spray foam is often seen as the perfect material for plugging medium-sized holes and gaps, mostly because it's inexpensive and easy to apply. I've used a lot of canned foam for air-sealing over the years, and I even wrote a JLC article that described some of my methods for working with it and other sealants ("Air-Sealing Tips and Tricks," 1/12).But as time passed, I began to have questions about canned foam's durability. I noticed in particular that pipes and wires would often break loose from the surrounding foam. I dissected foam samples and studied...