With Passivhaus it’s all about the numbers, and this 3400 square foot project has some amazing statistics — using cellulose as insulation, the home’s reduced thermal bridge wall system has an R-value of 52 and the roof is rated at r-97(!), or three times code. Even the concrete floor is super insulated with in-floor radiant heating added for those really cold days. The system is feed by a 700 gallon thermal storage tank and solar thermal panels, which also provide the bulk of the home’s hot water. All this work means that the only backup heating the house needs is a 3000 watt water heating element in the hot water tank.
While the energy numbers are impressive, the quality of the building is where the real fun starts. A core concern for Passivhaus design is the windows and doors – and the Optiwin units used for this project are sophisticated triple-pane and triple-sealed units with a wood and cork core. They are tuned to the building so they do not block the solar radiation to the south but keep the heat in by reducing thermal bridging with a U-value of 0.19 (nearly twice the efficiency of typical new windows). Full-height doors swing out to the enclosed patio but can also be tilted in to provide a fresh breeze. All the home’s windows can do the same thing – a common feature from European manufactures.