2013 08 07 the west side is looking complete, even though it’s not. the wall shown will eventually have 12″ insulation to its outside and 5.5″ of insulation to its inside. the outside of the wall that is shown in the photograph forms an air barrier or at least it will after all the seams between the plywood are taped. this along with the air barrier for the roof and the air barrier for the slab and tight windows or doors, will largely prevent air from entering or leaving the house. as a passive house, this air sealing will be tested with a blower door apparatus in which a fan will be sealed in one of the doors. it will pressurize and then de-pressurize the house. at a pressure of 50 pascal, the house may not leak more than 0.6 air changes per hour (ACH). just a few years ago, this was thought to be an impractical standard; but passive houses regularly achieve better than this. many houses will leak at a rate more than 10 times 0.6 ACH.
pascal is a metric unit of pressure that has somehow made it into the world of english units that are used almost exclusively in residential construction. 50 pascal is 0.00725 pounds per square inch. .