In the past, the Phius standard has been strictly performance based and required setting performance limits and whole-building energy modeling to verify compliance with those limits. In 2021, Phius released the first ever prescriptive passive building standard. Phius CORE Prescriptive was created to facilitate widespread adoption and scaling up, placing emphasis on quality, durability, health, safety, and cost-optimized conservation on the path to zero energy.
The prescriptive program was designed with the intention that projects that pursue either the performance (Phius CORE) or prescriptive (Phius CORE Prescriptive) path achieve the same level of building performance. The primary difference between the programs is the way that passive and active measures are regulated -- by individual items, subsystem performance tradeoffs, or by whole-building tradeoffs.
Phius CORE is available for all new construction projects.
Certification under Phius CORE Prescriptive is limited to single-family dwellings – detached or attached housing such as side-by-side duplexes or townhomes. Other notable limitations are the ratio of floor area to bedrooms, limits on window and skylight area and orientation and limits on "noncompactness" or building form.
Phius CORE allows for fossil-fueled combustion on-site, but requires electrification readiness for any combustion equipment. Phius CORE Prescriptive advances electrification efforts by banning fossil-fueled combustion on site.
Passive building provides a proven methodology for designing a net zero energy building. The first step is conservation — first through passive measures, then through active measures. Phius CORE targets the sweet spot for on-site conservation through both passive and active strategies.
Projects that meet Phius CORE achieve significant load reduction relative to a code-built building. This reduction lessens reliance on continuous support from the electric grid and can support load flexibility. This flexibility helps facilitate the integration of more intermittent renewable energy and reduces the total grid capacity needed to meet peak loads.