The Bishop Passive House in San Luis Obispo, California required continuous insulation to achieve Passive House certification and the targeted 85% reduction in energy use compared to traditional new construction. Traditional foam insulation could have provided the necessary insulation, but didn’t meet the project’s sustainability goals. The design team needed subslab insulation that satisfied Passive House Planning Package requirements, provided building comfort and efficiency, and kept the project under budget.
Achieving Passive House Institute certification requires meeting rigorous thermal performance standards that eliminate energy waste throughout the building envelope. The Cairn Collaborative team faced the following challenges when procuring materials for the build:
Foamed glass aggregate was the ideal material to meet the project’s diverse environmental and performance needs. Because foamed glass aggregate is made from post-consumer recycled glass, it aligns with sustainability goals and environmental requirements for the project. The closed-cell structure of foamed glass aggregate created an effective thermal barrier against the ground and concrete slab, preventing heat loss. The two person installation team spread and compacted the entire slab area in a single day with standard equipment, while the concrete team adjusted to a new material without issues. Foamed glass aggregate provided the needed continuous insulation while supporting the home’s airtight construction strategy without compromising the build’s efficiency.
