Well, we finally got the windows and doors installed. Okay, let me vent for a sec: prototypes are a bitch. We had to do a lot of head scratching and trial and error to figure out the best way to insure airtightness in our installation. The hempcrete is awesome, but it create its own set of challenges, especially since our truly wonderful Serious windows aren’t really designed to be installed in the middle of thick walls. (Serious is a partner with us on this project and we’re working with them to make things easier when you decide to replicate what we’re doing.)
First, let’s sing the praises of these 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 for a Passive House. 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, 1.0 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.
Why all the fuss? Well, I’ll tell you. In a Passive House in our climate region, walls need to be about R-40. Sticking an R-2 hole in an R-40 wall just doesn’t make sense. In a Passive House, 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.
Anyway, we’ve got video footage that we’ll eventually compile into a bunch of great educational how-to videos on the ins and outs of all this nifty construction detailing. If anyone out there is getting antsy for the goods, getting us a grant to fund collation of the documentation footage would really speed things up. Until then, wet your chops on these few photos: