Air Sealing
There is a measure for the amount of air leaks, or “infiltration” that passes through a building’s shell, and it can be determined by a blower door test. The test results for this measure of infiltration can sound rather abstract, but in fact, the amount of air that leaks or infiltrates a building’s shell has a significant impact on the energy performance of the building, as well as the indoor air quality. The benefit of a well-sealed building is that fresh air can be filtered and tempered through controlled intake and exhaust ducts and continuously delivered throughout the house to ensure a healthy indoor environment. To achieve Passive House Certification, the blower door test result measuring the air infiltration through the building shell needs to be less than .6ACH @ 50 Pascals – which is a very low and difficult number to achieve. As a reference for this level of infiltration, the average new home that is built (with attention paid to air sealing) is typically 10 ACH. Passive House requires a 90% improvement on the air sealing of its certified buildings. We recently conducted a blower door test on our prototype and were pleased to see the test results were so low that the machine did not register the amount of air leaking into the building at the standard test pressure. The blower door technician did not have a small enough aperture on his fan to measure the tiny amount of air passing through! 
The approach we used to achieve this level of air sealing on our building is based on planning the air barrier for the entire building from the foundation to the roof early on in the design process. We have also chosen durable construction materials for the air barrier, that are installed and sealed early on in the construction process. We find it much easier to seal the simple raw building elements before the many layers of insulation, utilities and finishes are installed, thus avoiding the complexities that happen later in the construction sequence. 
The foundation: A plastic vapor barrier was installed on the inside of the foundation that is continuous, sealed at joints, and sealed to the SIPs. Walls: The SIPs, which are considered air barriers unto themselves, are thoroughly sealed between the panels with both spray foam and tape. Because the panels are large, the number of joints between the panels is reduced. Ceiling: The air sealing at the ceiling is created by adding a durable layer of o.s.b. to the underside of the trusses, which is then taped at the joints to ensure air tightness. We choose o.s.b. instead of plastic for this barrier because of its durability in the construction phase and over the long term. Doors and Windows: The last and critical element of air sealing is at the openings for the windows and doors. In these locations we sealed the rough openings much like the joints between the panels with both foam and tape. In addition to sealing to the windows and doors, it is critical to choose windows and door products that are designed to have low infiltration rates as well. We find the European multi point lock hardware creates the best air seal for window and doors, and therefore have used these products on the prototype. You can read more blog posts about the GO Home here.
