Ask building professionals for the best method of air sealing and you’re likely to get a wide variety of answers. Most builders, designers, and consultants have selected materials and developed methods that work for them and meet their budgets. That being said, there are three fundamental steps based on building science than can lead to superior, cost effective, air sealing.
First, identify the building’s thermal boundary. For many situations and climates, a good location for the boundary is the exterior structural sheathing. This layer of plywood or OSB on a wood-framed wall already covers the entire exterior surface of the building. Second, use easily applied sealing materials that will adhere well to the surfaces to which they are applied and will not shrink, crack, or otherwise deteriorate over time. Third, test the effectiveness of the air sealing by using a blower door test to measure leakage and to check for leaks either with a smoke stick or by feeling for drafts. Many experienced builders prefer to run the blower door test while they are air sealing, a process known as blower door directed air sealing.Read More