After a hiatus of more than a decade, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is close to completing the update of the residential building code ASHRAE 90.2: Energy Efficient Design of Low Rise Residential Buildings. ASHRAE 90.2 is the companion standard to the better-known ASHRAE 90.1, which is the energy efficiency standard for commercial and high rise residential buildings.
The new code will provide a powerful tool to help advance energy efficiency in residential buildings, providing long-term cost saving, comfort and health benefits to homeowners and renters. It also will provide a template available to utility above-code programs, municipalities and states looking for stretch codes.
ASHRAE vs. IECC
ASHRAE 90.2 is a leadership standard in that ASHRAE intends it to be more energy efficient than current energy codes. Dwellings that meet this standard will use significantly less energy than a building meeting even the most recent energy codes. The foreward to the code says:
“This new Standard 90.2 seeks to deliver residential building energy performance that is at least 50% more efficient than the energy efficiency defined by the 2006 IECC.”
IECC is the International Energy Conservation Code, which is widely adopted across the nation as the energy code for residential buildings. The most recent code is the 2018 IECC, though 90.2 uses the 2006 IECC as a baseline standard to compare itself against.
ASHRAE 90.2 is a performance-based standard tied to aggressive Energy Rating Index (ERI) targets. In the most recent version of the IECC (2018), the ERI compliance path has values between 57 and 62 depending on the building’s climate zone (an ERI of 100 is roughly equivalent to the 2006 IECC and an ERI of 0 is a zero energy building). The proposed ERI values in ASHRAE 90.2 are slightly below 50. Moreover, ASHRAE 90.2 incorporates on-site renewables as well as enhanced sections on lighting and HVAC equipment. Finally, the standard has added sections on reporting and verifying results as well as guidance on verifying that the dwelling meets the requirements. While these sections are typically not included in codes, they are important to helping ensure that promised energy savings are realized.
Currently, ASHRAE 90.2-2007R (the name of the proposed update), is under public review. A first round of review is being completed, and there will be at least one additional round prior to final publication (targeted for the Fall of 2017).