CASE Passive House Low-rise Multifamily Reach Code Delivers Results!

The California Codes and Standards team (CASE) released their final analysis and review of PHCA’s Reach Code proposal and the results are truly remarkable! The summary findings show

“In almost all cases, the EDR Margins achieved by the Passive House designs exceed the EDR Margin targets, and in most cases, the Passive House EDR* Margin is significantly higher than the target EDR Margins defined in the report.”

The report presented some challenges in using CBECC-Res to accurately assess the benefits of buildings built to the Passive House standard, and perhaps explains why there are so few projects of this size currently utilizing this framework in California. (When you aren’t given adequate credit, you won’t be incentivized to use the methods standard to Passive House projects.) For this reason, the report allowed that “some modeling adjustments were made in CBECC-Res to be able to better evaluate Passive House characteristics.”

Not surprisingly, the primary challenges with comparison were:

  1. Infiltration: Passive House is famous for its rigorous air-sealing requirements while CBECC-Res assumes 7 ACH is adequate and does not require verification.
  2. Heat Recovery Ventilation: balanced ventilation is a new option for the Californian market in the 2019 code cycle. Not all climates in California require the heating/cooling energy recovery, but we found they all benefitted from their use – and offer surprising cost-effecitiveness opportunities to developers to eliminate other heating equipment in particular climates.
  3. Duct Leakage assesment: Passive House uses a whole house leakage test, and requires ventilation commissioning and balancing, but assumes ducts are within the envelope and don’t require additional leakage testing. This made ‘lost in translation’ issues a challenge.
  4. Attic Design: Our initial PHPP modeling used prescriptive Option C as a comparison. This results in a penalty in CBECC-Res because Option B (high performance attic) is assumed in the Standard Design in addition to ducts in conditioned space. (Another ‘lost in translation’ challenge!)

Most importantly, the resulting WHOLE BUILDING performance outcomes were rather spectacular! We generated a couple of graphs to show the results for you here:

The full report may be downloaded and read here.

Read more on our LinkedIn page here.

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(*EDR stands for Energy Design Rating. An EDR is an energy-use index, similar to the national RESNET HERS index, expressed on a scale that goes from 0 (a zero-TDV home) to 100 (a 2006 IECC code home. More details on this metric here.)