August 31, 2023

An earth-sheltered form fit for weather extremes

Hutchins

The Methow Valley, in the foothills of the North Cascade Mountain Range, is known for its access to nature, cold winters with abundant snowfall, and hot summers. The agricultural history in the valley is rich, and many small farms thrive today.

Sited amongst agricultural fields near the historic McKinney Mountain, the Berm House — part of a complex under development in the valley — is built into a meadow slope. It will informally serve as a common house for the larger, 19-house mixed income community.

Cold climates call for particular design elements to facilitate passive solar heating and cooling, and the cyclical changing of seasons. Planning for these strategies involved a detailed analysis of the site which sits between the Methow River on the east and McKinney Mountain to the west.

The north side required protection from winter winds, while the southern exposure needed to be designed for solar heat gain in winter and to limit solar exposure in summer, while maximizing territorial views. At the east, the winter sun tucks itself behind McKinney Mountain right around noontime, and the west side would provide Highway 20 access. Considering these factors, as well as the site’s orientation, it became clear the general form and massing of the architecture would be a key consideration throughout the design process.

Photos by Benjamin Drummond [enlarge]

A simple and compact shape with a sunken terrace to the south acts as a windbreak and private patio for the bedrooms.

[enlarge]

The Berm House design incorporates Passive House principles including superinsulation, advanced air sealing, and mechanical ventilation.

The home’s low profile opens to the valley panorama of mountains and agricultural fields while remaining virtually invisible from the McKinney Ridge residential area to the north. The south-facing building orientation optimizes passive heating, and the large overhang protects from snowfall and intense summer sun.

With the earth-sheltered strategy, other elements of the design became important and dependent on this approach. A simple and compact shape with a sunken terrace to the south was integrated into the design to act as a windbreak and private patio for the bedrooms. On the east and west facades, ‘wing walls’ complete the berm, provide privacy, and focus the views down the valley. Toward the north, a formal entrance is located between two berming mounds acting as a focal point yet integrates with the design scheme.

The home is post and beam structure with a Cross-Laminated Timber (CLT) roof, prefabricated in northeastern Washington. The design incorporates Passive House principles including superinsulation, advanced air sealing, and mechanical ventilation. Thermal bridges are minimized by wrapping the house in continuous external insulation, including under the foundation, isolating the home from outdoor temperature swings and the brisk winter wind.

The bermed roof, with 12-inches of soil, adds thermal mass and protection from weather exposure and fire. The roof will feature a path through the native landscaping. The Methow Valley’s original one-room schoolhouse will be placed on the roof and oriented toward a peak that holds personal significance to the owner and be open as a space for reflection.

Guided by the client’s community-oriented vision, a significant design request emerged: the ability to host guests, allowing privacy and independence for everyone. A great room was designed for friends and neighbors to gather regularly. Off the great room, a five-foot wide hall leads to three guest suites and the primary suite. The uncomplicated and efficient floor plan shows a clear division between the private and public spaces.

Varying sunlight exposures, seasonal warmth, and views are maximized along the entire south-facing wall of the heavily occupied great room and suites. The south facade is outfitted with floor-to-ceiling energy-efficient windows that intend to allow the winter sun in fully, yet be efficient enough to protect the interior environment from indirect summer heat. The mechanical and storage areas are located where sunlight is not required and there is a desire for dark, cool, and dry spaces.?Back-of-house includes a large pantry, with access to a crawl space for storage, and a laundry room.

Unique openings and strip lighting accentuate the wood beams. The CLT ceiling, wood panels, deep gray slate floors and black horizontal fixtures unify the space. Dark hickory on the floor in the hall and suites add continuity. A coffee table and the kitchen bar were crafted from a fir tree felled off the property. Landscape boulders were sourced from a quarry on the property as well. The homeowners’ quarry informed the rocky landscaping theme.

Matt Hutchins serves on the Seattle Planning Commission, is a strategic councilor for AIA Washington, is on AIA Seattle’s Board of Directors, and is co-chair of the public policy board. He is a co-founder of CAST architecture.

Other Stories:

• Embracing the mass timber revolution
  
• Concrete can be part of your sustainability equation
  
• UM looks to mass timber to mark forestry heritage — and future
  
• Setting a new sustainability standard for affordable housing
  
• Reshaping sustainable design with mass timber
  
• Mass timber building spotlights Washington’s roots
  
• The design logic of decarbonization