For the past decade, Duluth architecture and research firm Coulson has been refining a design approach that yields highly sustainable buildings using simple, “invisible” methods—all without compromising the aesthetic creativity that clients long for. Founder Carly Coulson, AIA, a signatory to the American Institute of Architects’ 2030 Commitment, shares her firm’s process with Architecture MN.
SENSE OF PLACE
Imagine it’s 40 below on a January morning in Northern Minnesota. The snow is gently falling on a grove of lovely white birch. Though outside conditions are brutal, inside one experiences both thermal comfort and a seamless connection to these beautiful natural surroundings. Yet no active heating is being used. The design focus is purely on the poetic sense of place that the architecture and landscape create.
Building owners can achieve near-zero energy and AIA 2030 targets without high-tech gadgetry or renewable-energy systems. Simple, permanent, passive, and invisible methods meet the highest levels of sustainability without impacting the aesthetic creativity that is crucial for design excellence. With a conservation-first approach, the emphasis is on the building envelope and near-elimination of heating and cooling loads. This alone achieves a 70 to 80 percent primary energy reduction.
INTEGRATED, EXPLORATORY DESIGN
Advanced energy modeling is used to analyze the methods and details to achieve deep energy reductions. At Coulson, we use the Passive House Planning Package. Taking both a precise and an exploratory approach, we respect the fundamentals but allow time to test our creative expression and challenge expectations of green building. Architects can take the lead on climate change with their unique position to develop integrated designs while incorporating energy modeling into their daily design process.
NO THERMAL BRIDGES
The focus is on systems that maximize continuous insulation without thermal bridges (paths of least resistance for heat transfer) and without increasing costs. Our modern transparent designs with interior steel structure use prefabricated, large-format components that reduce onsite construction time and risk. Twelve-inch-thick blocks of EPS (expanded polystyrene) quickly assemble into super-insulated formwork for concrete slab-on-grade foundations. For the roof, 12- to 16-inch-thick jumbo SIPs (structural insulated panels) install fast. Smart tapes and membranes create a continuous airtight layer around the exterior envelope.
WINTER PASSIVE SOLAR
Even in Minnesota’s extreme-cold climate, architects can design for exterior transparency and a fluid connection to the outdoors. By using triple-pane insulated glass with careful attention to thermal value, SHGC (solar heat gain coefficient), and orientation, it’s possible to capture winter passive-solar heating while integrating shading to maintain optimal interior thermal comfort. With many years of research on glass performance, cost, and partners, we’ve developed attainable solutions for buildings that are almost entirely glass.
A compact building form minimizes exterior surface area, which greatly reduces heat loss. A good way to achieve this is by reducing the building height. When paired with floor-to-ceiling glass, a lower ceiling height is hardly noticeable. This strategy also reduces glass material costs and affords us the freedom to break the compact-building-form rule with a bump-out or cantilever where it is critical to the design.
Continuous, balanced ventilation is essential for occupant health, but we keep the HVAC simple and right-sized. For residential projects, a through-wall ductless HRV (heat-recovery ventilation) system with 90 percent efficiency is a great option. Eliminating ductwork allows for super-thin floors, tying back to that compact form. The peak heating load varies from about 100 to 2,000 watts for Minnesota projects. This micro-load can be satisfied with plug-and-play solutions like a radiant electric panel, a simple lamp, or a mini-split heat pump.