Also known as Title 24 (Part 6), the standard defines ZNE as consuming only as much energy on an annual basis as can be generated on-site with a renewable energy system. To promote the renewable energy aspect, reported Joe Hayden (Pella) during the AAMA Western Region Summit, the 2019 standards make California the first in the nation to establish solar photovoltaic (PV) electricity-generating systems as a prescriptive requirement.
To meet the goal of substantially reducing a home’s impact on the electrical grid through the use of PV, grid harmonization strategies are introduced that offer compliance credits for PV accompanied by battery storage.
The standard is based on 16 defined climate zones across the state and includes mandatory measures (that always have to be done), prescriptive standards (which, per Hayden, can sometimes be too restrictive for builders and designers seeking credit for installed features) and an alternative performance approach based on computer calculations that allows trade-offs (e.g., more efficient windows vs. more efficient air conditioners). So far, more than 90 percent of all compliance is achieved via the alternative performance approach.
“To navigate compliance, you must know what the compliance documents say,” said Hayden.
The 2019 standard tightens prescriptive requirements by continuing the 20-year trend of reducing maximum permissible residential window U-factor to 0.30 statewide, and SHGC to 0.23 (except in climate zones along the coast and in the northern/northeastern mountainous regions where there is no SHGC requirement). Replacement windows must meet the same requirements, except up to 75 square feet can have a U-factor of 0.40 and an SHGC of 0.35. The prescriptive U-factor for non-fire-rated doors, which had held steady at 0.50 through 2016, now changes to 0.20. The door U-factor limit applies to exterior doors with less than 25 percent glazing; those with more glazing are treated as windows. Skylights are limited to 16 sq. ft., with a U-factor of 0.55 and an SHGC of 0.30.
Hayden showed an example of the performance approach in which ZNE is achieved (compared to a 2006 IECC-compliant design) through a combination of photovoltaics, a more energy-efficient HVAC system, and reconfigured lighting, appliance and plug loads.
On the commercial side, prescriptive values are the same in all climate zones and remain unchanged from 2016. National Fenestration Rating Council (NFRC) ratings (traditional or Component Modeling Approach) are necessary to meet the prescriptive values and to get full alternative credit for product performance.
The California Energy Standards are updated every three years, and work is aleady underway on the 2022 version. A variety of stakeholder workshops will be held to better define metrics through 2020, and the drafting of the updated standard through various hearings will begin in 2021. To get involved, visit title24stakeholders.com.
Hayden acknowledged and expressed appreciation for the contributions from Ken Nittler, President of WESTLab, to Hayden’s report and presentation.