At 3715 SE Division in Portland, Ore., the nation’s first commercial Passive House retrofit is taking shape. The site of a former guitar store (and before that, a barber shop) and a couple of apartments, the building is currently undergoing an extensive remodel designed to take its heating and cooling needs down to the bare minimum with a minimum of added cash. The project, known as the Glasswood Passive House Retrofit, is currently on track to meet Passive House’s rigorous green standards at only $15 per square foot more than a conventional remodel.
In accordance with those standards, the building must achieve an airtight building shell (as established by a blower-door test) with less than an .6 Air Changes per Hour (ACH); an annual heat requirement of less than 15 kilowatt hours per square meter per year (or 4.75 kBTU per square foot per year) and use no more than 120 kilowatt hours of electricity per square foot per year in total.
The project — designed by Scott Edwards Architecture and built by Hammer & Hand — makes use of a number of green building products and strategies to meet these prereqs, including a Zehnder heat recovery ventilator (to ensure fresh air gets into the airtight building, without losing heat) coupled with a ductless, mini-split-system heat pump system; SIGA vapor barrier tape (to ensure moisture moves evenly through the wood substrate); and Cascadia triple-pane windows with insulated fiberglass frames and tuned glazing (to allow for strategic solar gain, based on the building’s passive solar orientation).
The Glasswood Retrofit will only manage to bring the top half of the building into accordance with Passive House standards (designers found that the cooling challenges of commercial cooking equipment for the restaurant slated for the space below insurmountable on those terms), but the entire building, when complete, will nevertheless be one of the greenest in Portland, a city full of green buildings. It was designed using Passive House Planning Package, an Excel-based software program.