Montana Passive House Built to Withstand the Region’s Harsh Winters
Residents of Brooklyn, New York, Ryan and Margo Reynolds had a few requirements for their second home to-be in Montana. They had specific criteria for the distance from “town” and the airport, views, privacy and quality of the landscape, and sought out Love Schack Architecture prior to finding a lot to build on, which proved helpful as the firm helped them compare available build sites that met their needs.
“This ultimately led to them committing to the lot in Bridger Canyon,” says Lindsay Schack, principal at the firm. “It was helpful, of course, that their very close friends had just purchased a building site in the canyon and there was a lot available next door.”
The biggest goal of the project was to meet Passive House standards, which the team at Love Schack and builder CWJ & Associates have much experience in. Homes built to Passive House standards are airtight, insulated structures that can maintain a comfortable thermal temperature with minimal energy input. Schack shared that this can be achieved through five principles: airtight building envelopes; thermal bridge-free design (no leaks at joints or corners); building assemblies that have insulation amounts that respond to the climate (this is more for cold climates); balanced ventilation with Heat Recovery, and high-performance windows and doors (high solar gain, low transmission heat losses).
“The design process is not that different from any typical home, with the additional layer of energy modeling and confirmation that the assemblies, windows and doors, and mechanical systems are properly sized and will result in a building that needs very little energy from the grid to keep the interior around a comfortable 68°F–70°F while providing constant fresh air to the interior,” explained Schack. “The build process is perhaps the most crucial and different, but only because of the importance of working with a knowledgeable contractor who can sequence the work and carry out the design intent. Building a passive house is meticulous when it comes to installing the air control layers of the assembly, so it requires care and attention.”
According to Sunset, Montana’s climate zone does provide a challenge when designing a passive home. Lindsay says that the goal when designing is to prevent adverse effects in the home when the outside temperature is very low, like -15°F, and the interior temperature is 70°F, because this type of scenario can result in condensation forming on the windows or walls if the assembly is leaky. The condensation might then contribute to mold growth and unhealthy indoor air.
“When we have robust assemblies, and the airtightness of it prevents the thermal transfer through the assembly, we can avoid this moisture problem,” Lindsay says. “The method, however, works very well in our region as we have lots of sun all year, which helps to balance out the energy needed on cloudy days or long stretches of stormy weather. If the power were to go out, this home would stay consistently warm enough for comfort for several days.”
