August 2023 - Vapor, Air Leakage, and Why Your Wall Needs to Breathe

Jeff Flaherty brings in Corey Murphy, product consultant at 475 High Performance Building Supply and adjunct professor at RIT, to talk about what actually makes a wall assembly durable. Corey walks through the hierarchy: keep bulk water out first, then address air leakage, then manage vapor. He explains why closed cell spray foam, despite its high R-value, can trap moisture with nowhere to go, and why vapor-open materials like rock wool, cellulose, and hemp distribute moisture instead of concentrating it. He also covers Intello, a smart vapor retarder that changes its permeability based on the humidity in the wall, essentially opening up to let moisture dry out when conditions call for it and closing back down in winter. Plus the HRV versus ERV debate, why an ERV is usually the right call in this climate, and why putting solar panels on a 15-year-old roof is a bad investment no matter how shiny the panels are.