Improving Envelope Performance
Repeated energy modeling was a key way that HKP experimented with multiple solutions. They could test different inputs to see how the building’s Passive House compliance was affected, fine-tuning as they went.
“In simpler, less complex projects, you generally model once and that’s sufficient. But larger projects benefit from ongoing modeling,” explained Blazek. “Whether it’s small or significant, it’s worth seeing the impact from one change.”
One outcome was creating a subceiling framing system between the library level and the garage floors above. This reduced the number of penetrations for mechanicals, lighting, and electrical, and suspended ceilings into the Passive House envelope itself. The interstitial support system is insulated with thermal break pads.
“Another example is we had debate about insulating the footings. Our energy modeling showed we could insulate the tops and sides down to 3 feet, but there wasn’t much return beyond,” Blazek said. “We also insulated the major sheer walls from the parking garage so none of them communicate with the interior environment. No cold air is transferred to the column as a result.”
While no project goes without a hitch, bumps in the road can sometimes compel creative choices that contribute to the building’s performance.
“We originally picked fiberglass windows with a krypton gas, but they were made in Ukraine and became unavailable. We had to choose another window package with argon and remodel accordingly,” explained Blazek. “A similar conflict happened when our first insulation option for mineral wool had a plant strike and shutdown at the same time. We moved to fiberglass, which has a different R-value, and reran the model.”