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This is the final part of our four-part series exploring passive house design as it relates to Elk Ridge Passive House in the Rattlesnake Valley. So far, we have explored Passive House standards and principals (Part 1), site evaluation and balancing a “wants and needs” list (Part 2), and the process of material selection (Part 3). We will conclude the final part of our series by discussing the window and door selection, mechanical systems, and air sealing methods and materials.  A home built with intention while maintaining the strict passive house design principles creates a long-lasting high-performance structure. Each of these elements combined provides efficiency, which directly contributes to a home that is comfortable for its occupants year-round. Our home owner’s, along with their building team, have navigated this process with diligence and thoughtfulness.

Window and Doors

Fixed Windows

The Glo CW7 curtain wall system was selected as the primary window system for the house. Given that the house has such a large glazed area, performance was key. The curtain wall system provided the smallest visible frame area, plus high performance. The aluminum frames were elected for their clean lines and durable, low-maintenance powder-coated finish. Furthermore, the 5’ overhangs and external shades furnish additional protection from overheating. A higher solar gain glass option was designated in order to yield the largest amount of free heat in the winter time.

Tilt Turn Windows

With careful selection, for design and ventilation, Larch tilt-turn windows will be inserted into the aluminum curtain wall system. Although this approach is a bit unconventional and has never been done before (that we know of), it provided to be a very high performance window. The beautiful warm wood finish counter-balances the industrial concrete walls and aluminum curtain wall in this dynamic passive house design.

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Entry Doors

Larch entry doors were selected for their exceptional performance value and aesthetic. The wood entrance creates an inviting foyer against the diametric style of the concrete exterior.

Lift and Slide Door

A 20’ Lift and Slide Ultra door will be installed in the basement family room. The generously sized door has only two leaves emulating an open feel, filled with views and intentional natural lighting. Given the size, material consistency, and higher exposure due to its location on the building, an Aluminum frame was chosen. The durability of thermally-broken aluminum, coupled with an air-tight seal that the Lift and Slide doors are famous for, ensures desired efficiency and performance.

Mechanical Systems


A Ground Source Heat Pump was utilized for the Elk Ridge heating and cooling system. Here are the key reasons for this selection:

  • All Electric, allows us to offset our use with solar production
  • We did not want to see a condensing unit on the outside of the building
  • Ground source heat pumps are extremely efficient.

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Domestic Hot Water

A ground source heat pump will be utilized to produce the majority of the domestic hot water. The Climate Master Trilogy 45 Q Mode is capable of producing space heating and cooling as well as domestic hot water. In addition, all of the hot water lines will be insulated. Insulating the lines with reduce heat loss and aid in hotter water temperatures allowing for lower water temperature settings. Plus, insulated lines create a shorter wait time for water to warm up, ultimately conserving water.

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A Zehnder Comfo Q was selected for the ventilation system. Unfortunately, this unit had to be imported from Europe, because at the time of the house being built, it was not yet available from Zehnder USA. This particular ERV stands out due to its stellar efficiency, user friendly controls and Zehnder’s reputation for durability. Thanks to Skylar, Elk Ridge’s Passive House consultant, for introducing the product!


Air Sealing Methods

Elk Ridge Passive house was designed with a continuous air barrier for dynamic air sealing. The continuous air barrier runs along the bottom of the slab all the way up and over the roof, additionally incorporating windows, walls, roof structure, and every connection between the various systems. This creates an air-tight building envelope with long-lasting impermeability.

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Air Sealing Materials

Quality air sealing products are as important as their application and should be considered with care. These products must be air-impermeable, durable and must perform their function for the life of the home. Here is a list of the products utilized for Elk Ridge Passive House in order to achieve an air-tight envelope:

  • EPDM Gaskets
  • Siga and Tescon Tapes
  • Sealants: Prosoco, Sika Flex, Tremco, Dow
  • Plywood
  • Intello
  • Siga Majcoat and Majvest
  • Spray Foam
  • Rigid Foam Board


The hope of this series was to demystify the Passive House method of building, providing guidance for others as they pursue their own Passive House design.  Although this is the first passive house in Missoula, Elk Ridge is uniquely positioned to usher in a new wave of building for the state of Montana …and beyond. We hope you learned some key principals in Passive House design and are ready to apply them to your own building project(s) –Happy building!

To see more of the Elk Ridge Passive House journey, please check out the Elk Ridge Passive House Instagram page: