I decided to attend an event hosted by the AIA in Eugene. It turned out to be pretty interesting, as it covered some current passive house strategies. The "Kiln" Apartments designed by GBD Architects (one of the first multifamily projects to pursue the passive house standard in Oregon) were used as a case study, and was presented by David Posada, sustainability manager of GBD Architects.
Some history: The Passive House movement originated from Germany, and uses strategies that are passive in nature, most importantly air tightness and active ventilation. The first passive house in the U.S. was done in Urbana Champagne, Illinois in 2005. It was designed after the first passive house in Germany in 1990.
Kiln Apartments: a mixed use (commercial on bottom floor), multifamily passive house. Designed by GBD, completed in June 2014. To perform as a passive house, this building uses continuous insulation, continuous air barrier, premium/high performance windows, balances solar gain to shade, balances active ventilation with heat recovery, minimizes heating and cooling using ventilation ducts, uses efficient appliances and lighting, and is thermal bridge free.
Heat loss occurs mostly from ventilation, while heat gain occurs from heating.
Walls could be done in two ways, the first would be double studded, or stud and foam done in which 2x2 posts sit at the ends of the bottom plate, and 2x4 studs are offset in order for insulation to be continuous in the wall. It appears similar to this. The windows are all airtight, and pay close attention to the U-value, the heat gain, and the thermal bridging. The air tightness of these windows are 6ACH (air changes) at 50 pascals. A typical "energy star" home would have about 3-5 ACH. The "tilt turn" windows were used for this building, and, according to the architect sitting beside me, the most energy efficient window type. These triple pane, wooden windows were produced by "HH Windows" in Seattle (UV= .12 and .13, SHGC .56 South facing, SHGC= .25 North, East, West facing). Exterior cladding was used to protect the wood from moisture. The architects also built a mockup window to test the performance (they also used a blower door to test the air tightness of the building). The architects also used fluid applied air barriers from "Prosoco".
The Kiln apartments have lots of corner units which was interesting as a design perspective, as it provides maximum view potential for the units (this was done by using somewhat of an L shape).
Some lessons learned from the architects:
1. Skin to volume ratio for the project: 4.9 vs 7.9
(exterior envelope vs interior volume)
2. Orientation: Broad side at North and South, minimal glazing at East and West
3. Insulating ground floor is important (lots of heat lost to the ground). It is generally best to pay attention to window selection, insulating the roof, heat recovery ventilation systems, and exterior wall insulation.
These are some pretty basic notes, but it was really great to see some of the strategies learned in class being applied to real world projects.