Posted on September 26, 2012 by Roger Normand in Guest Blogs
[Editor's note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the ninth article in a series that will follow their project from planning through construction.]
Strike up the band: we have – finally – achieved the Passivhaus standard with Unilux windows!
Marc Rosenbaum, our energy consultant, ran the Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Planning Package (PHPP) energy modeling software and arrived at a heat load of 4.74 KBTU1,000 Btus/sq. ft./year, a mere 0.01 below the 4.75 limit. Talk about a photo-finish squeaker!