When building a passive house, highly efficient windows must be used. The original drawings of Project Green Home specified Sierra Pacific windows and doors, but we have since decided to install Sorpetaler windows. As a Window Specialist, Passive House Consultant, Bronwyn Barry often finds herself in the position of ‘Window Evangelist’ these days. From brand selection, to cost, to carbon footprint, she shares with us the insight and reasoning that went into choosing the windows for PGH.
We have been building with Sorpetaler doors and windows for many years, mostly because we have not found a locally made equivalent for either quality or performance. I don’t make this claim lightly. Below is a performance rating comparison that I’ve compiled, including a few well-know brands. Of course, the quality component is hard to quantify and insert into a table.
In a Passive House, energy performance is the certification goal. However, comfort and indoor air-quality have played major roles in establishing the energy compliance targets. By simply increasing the window glazing from double to triple-pane, both the comfort and performance of a building are enhanced for a surprisingly low incremental cost increase. People are always surprised when I tell then that the cost increase for ordering triple- versus double-pane windows in the Sorpetaler line adds approximately $800 TOTAL for the whole house (contingent on the size and number of windows). Glass is cheap. When you buy good windows, you are paying for the frame, not the glass!
Another common reaction upon hearing that a client/builder/architect has selected a German-made product is to ask about the carbon footprint for shipping? I too made the assumption that the distance these windows travelled automatically increased their carbon footprint. The architects for Project Green Home, Arkin Tilt, prompted an actual calculation for this and we were all surprised by the outcome (see below chart). I have subsequently done the carbon footprint calculation for a number of destinations around the United States and it’s very hard to find a local product that performs comparably, with a lower transportation carbon footprint.
For more ‘pearls of wisdom’ from Bronwyn, she will be delivering two presentations on this topic in the near future. The first one is this week at the West Coast Green Passive House Pre-Conference (Project Green Home is proud to be part of both the Pre-Conference presentation and included in the Passive House California Open House Tour on October 3rd). The other presentation will be at the US Passive House Conference, to be held in Portland in early November.