Passive House California (PHCA) recently submitted their first Reach Codes study to the California Energy Commission’s (CEC) consultant team charged with analyzing the cost effectiveness of all proposed code improvement measures. The study specifically looked at improvements required beyond compliance with the 2019 energy code, for a low-rise multifamily building, to meet the equivalent performance targets set by the international Passive House Standard. The study not only uncovered a gaping hole in the current compliance software, but revealed two exciting opportunities to easily improve building energy efficiency (plus comfort and durability) for this building type.
Gaps in energy compliance software:
At the start of the analysis it was discovered that neither California’s 2016 nor 2019 building energy code requires multifamily buildings to achieve any measure of airtightness. In fact, the currently approved compliance software model is unable to gauge the improved efficiency of a tighter building envelope for California’s multifamily buildings. The study required generating a similar sized building using the modeling software typically used for single family residential building compliance. Full details of the methodology used may be read in the report, but simply identifying this missing opportunity to accurately predict energy use in current multifamily building compliance software was by itself a major finding.
Other key discoveries:
By applying the consistent performance targets characterized by the international Passive House Standard, to all sixteen of California’s climate zones, the study identified opportunities for increased envelope improvements in some climate zones, while showing code requirements in others to already be in line with PH targets. For example, no additional insulation was required for the San Francisco model, while a 2019 code compliant Sacramento multifamily building would require additional R-8 insulation to both the walls and slab to meet PH performance outcomes.
Airtightness and E/HRV’s win everywhere:
Once Passive House airtightness levels were identified as an easy win in all climates, appropriate ventilation measures were carefully assessed. While the models showed that Passive House performance targets could be met without H/ERV’s in some climates, heat recovery ventilation (with a minimum recovery efficiency of 70%) still improved performance consistently across all climates. Given this equipment’s additional filtration and balanced pressurization benefits, particularly after the 2018 firestorms which ravaged our state, the team felt more comfortable including H/ERV’s in lieu of simpler, extract only ventilation options.
Next steps:
While the impact of this study on both the 2019 regular code and reach codes are still being evaluated by the CEC’s Codes and Standards team, funding for additional studies is being sought. This first study focused solely on one building type: low-rise multifamily–a constraint driven partly by limited resources, but also a calculated selection. Multifamily buildings offer an increased opportunity to reduce California’s carbon emissions by reducing vehicle miles traveled. More pointedly, the PHCA Board recognizes that there are currently no large multifamily developments targeting Passive House certification in California (that we are aware of), despite availability of tax credits for affordable housing developments seeking certification. Hopefully the surprisingly attainable improvements highlighted in this study will change all that, plus provide the CEC with a helpful resource to further align California’s building energy codes with California’s ambitious energy policies.
READ THE FOLLOW UP CASE REPORT (confirming the results of the above study) HERE.
