THE 2025 AWARDS

Douro Farmhouse is a two-storey straw bale house on a walk-out basement on a family farm near Peterborough, Ontario. Thanks to BEAM and the following innovations to decarbonize and add carbon storage, we achieved an impressively low MCI of just 28 kg CO2/m2 on this build. STRAW BALE WALLS: The biggest climate hero on the job site is also our signature work. Tightly fit between a double row of studs, the 360 bales store 9,588 kgC02e. They are also locally sourced, highly regenerative, non-toxic, and offer excellent thermal performance, which reduces the family’s operating emissions and utility bills. It’s a win-win. NATURAL PLASTER: The exterior and the interior of the straw bale walls are sealed and finished with clay-lime plaster. It adds structure and air, weather, fire, pest, crack control, and beauty to our straw bale walls. The chopped straw fibre adds carbon storage, and the clay and lime binders reduce carbon emissions by eliminating cement. SUPPLEMENTARY CEMENTITIOUS MATERIALS (S.C.M.): By choosing a concrete with the same strength but a 50% S.C.M. content from our local supplier, we decarbonized the 8” poured foundation wall by approximately 30% in just one phone call. I wish it were always that easy! SLABLESS SLABS: Instead of calling the concrete truck back to pour a slab in the basement, we compacted a 5” base of limestone screenings over GLAVEL insulation and topped it with a 3/4” earthen floor. We used 6” staples to pin the radiant PEX to the screenings instead of tying it to high embodied welded wire mesh. Similarly, on the main and second wood frame floors, instead of concrete, we overpoured the radiant PEX with 1.5” of limestone screenings followed by a 3/4” earthen floor. We use cement, but sparingly - mostly for below-grade and structural applications. EARTHEN FLOORS: The earthen floors are glossy, hard, and water-resistant. They are similar to polished concrete except that the binder is clay instead of cement. On this project, we installed earthen floors on all floors, totalling 3,400 sq. ft. It’s our largest earthen floor and Ontario’s largest too. At just 3/4” and consisting primarily of clay, sand, and hardening oils, this innovation is more in spirit than in draw-down reality like straw bale walls. There is some carbon storage in the chopped straw added as fibre, and earthen floors, top and finish slabless slabs which offer significant carbon emissions compared to a cement-based concrete slab. Check, check, these innovations work together. GLAVEL: Straworks is a foam-free company. Since 2015, we haven’t used foam for its high embodied carbon and toxic ingredients. On this project, as an alternative to foam or Rockwool board, we installed 33 cu.yds of Glavel as sub-slab insulation. It is also replacing the 4” layer of clear stone required by the Ontario Building Code to depressurize soil gas. Glavel is an insulative aggregate made in Vermont from recycled glass in an electric kiln powered by renewable energy. It is also water-resistant, non-combustible, inert, and load-bearing yet lightweight. CELLULOSE INSULATION: The basement below-grade and walkout walls, cathedral ceilings, attic, some framed floors, and some interior walls are insulated with cellulose insulation, which adds up to an impressive 2,642 kgC02e of carbon storage. Versatile, carbon-storing and highly insulative, cellulose is our second favourite insulation after straw.