A quadruple pane window from Serious Materials installed in a hempcrete wall of the Nauhaus Prototype

The Nauhaus Prototype project hit a milestone this month with the installation of doors and windows form Serious Materials. The project hasbeen designed to reach the Passive House Standard and therefore requires extremely high performance windows.

Though a number of German companies make windows in this category, Serious Materials is the only US company that can meet the required specs. All window and door units on the project have fiberglass frames and quadruple pane glazing. Southern glazing has a center of glass insulation value of R-7 with an impressive solar heat gain coefficient (the percentage of solar heat that passes through the glass, 1.o would be 100%) of about 0.7. This allows for heat gain from the low southern winter sun, a strategy integral to the Passive House integrated design system.

North, east, and west glazings weigh in at an amazing center of glass rating of R-11, a rating equal to the fiberglass insulation in some conventional stick frame walls! This is compared to R-2 for a typical double pane window found on most US projects. Unlike the heavier European windows, Serious reaches this performance level with two pieces of glass and two pieces of plastic allowing for a thinner profile more like conventional windows typically available in the US.

“In a Passive House in our climate region, walls need to be about R-40. You just can’t stick an R-2 hole in an R-40 wall,” says Clarke Snell of the Nauhaus Institute. “The idea is to spend money on passive elements, extra insulation and really good windows for example, that don’t require energy inputs to do their job once installed, unlike heating, cooling, and ventilation equipment. In the right configuration, these passive elements combine to allow for a much simpler and less expensive mechanical system, thus saving money in construction and afterwards with much lower energy bills.”