“I like the analogy of ‘putting the energy code on the doorstep of Passive House,’” Mike told me over coffee recently. “Fundamentally, what we were trying to do was take our existing 2015 Washington code and, with the new updates, take it to the doorstep of Passive House. Code has now moved from across the street, up the front porch stairs, and onto the doorstep. Now it’s just a matter of ringing the doorbell or knocking on the door—that’s the distance between where we are and Passive House certification.”
For the residential side of Washington’s building energy code, the Passive House progress made in the past year is simple to explain. That is, if you build a PHIUS (Passive House Institute US) or PHI (Passive House Institute) Passive House-certified home in Washington, it is automatically compliant with Washington energy code. A home’s building permit can be issued upon receipt of a pre-certification letter from PHIUS or PHI, and certificate of occupancy can be issued when PH certification is completed. Kudos to Graham Wright of PHIUS, Poppy Storm of the 2050 Institute, and Shift Zero for leading the effort to make this happen.
Progress on Washington’s commercial building energy code is a bit more complex to explain, but no less important. Mike took PHI’s “low energy building” metric as a guide for bringing new buildings to the “doorstep of Passive House”: namely, the metric’s heating demand target of 9.5 kBtu/sf/yr. He then employed three additions to Washington’s commercial energy code to get new buildings there: new airtightness requirements, new HRV requirements, and also a standalone outcome-based energy budget path.
First, building airtightness will now be a required 0.25 CFM75 (an air infiltration rate of 0.25 cubic feet per minute at 75 pascals of pressure) or better, based on the Army Corps of Engineers airtightness standard. While this is three times more permissive than PHIUS+2015 0.08 CFM75 metric, the requirement is nonetheless a big step and a significant reduction from the previous 0.40 CFM75 requirement. For the first time in Washington teams must meet the standard (rather than just report on airtightness), and it should demystify air sealing and measurement in the industry. Moreover, a more stringent 0.17 CFM75 target also shows up as one of the option choices on a menu of additional efficiency measures; teams are required to choose options from this menu that will total 6 credits, so there’s an incentive to overperform on the baseline 0.25 CFM75 target.
Second, multifamily buildings (4 stories or higher) are required to incorporate balanced Heat Recovery Ventilation (HRV) with a minimum 60% efficiency. Again, this efficiency level is not quite Passive House, but it’s clearly on the doorstep. While the HRV efficiency could be higher, the indoor air quality benefits for residents will be significant. And if teams are already specifying HRVs in all multifamily buildings, it’s a relatively small lift to bring them to Passive House-level efficiency.
Finally, local jurisdictions can now opt to adopt outcome-based energy budgets, meaning they can now choose to require commercial buildings to measure energy use and demonstrate a full calendar year of energy use that is in compliance with maximum energy use targets specified for 11 occupancy types. These maximum energy use targets are calibrated to be consistent with code’s progress toward the 2030 target mentioned earlier (70% better than 2006 code by 2030).
Mike says that these measures, particularly airtightness plus HRV, results in a heat demand of 9.7 kBtu/sf/yr for a 4‑story multifamily building—very close to the 9.5 kBtu/sf/yr “low energy building” target set by PHI and even lower heat demand in the 10-story prototype modeling at 8.2 kBtu/sf/yr, and right on the doorstep of Passive House.
When Mike explained his approach to me, it made me reflect on a dynamic I’ve encountered while advocating for Passive House design and policy. For most audiences, you can talk about airtightness, heat recovery ventilation, a bit more insulation, good windows, smart energy modeling, and you get lots of heads nodding in agreement. All of that seems like a commonsense approach to making better buildings. But, say the words “Passive House” and the tenor of response can really change: “Woah, woah. Let’s not get carried away!” For some, “Passive House” seems radical, even when the core elements of Passive House design are totally reasonable.
“That is so true,” Mike agreed. “I got past that by saying this was a proposal from Passive House Northwest, but never mentioning the words ‘Passive House’ again. Instead, I spoke about how these were proposals to help the state move further on the path toward our goal to see 70% reduction in new building energy use by 2030. It was all about helping the state move towards its goals.”
Mike focused on the energy savings benefits of his proposals, but also the health benefits.
“Before these updates, mechanical ventilation in multifamily buildings just wasn’t a thing here,” Mike explained. “You could poke a hole in a window frame or have a big, open duct to exchange air—that and an exhaust fan in the bathroom—and that was your whole house ventilation.”
By emphasizing the very real health benefits of an inherently energy efficient technology—HRVs—Mike was able to advance commercial code much of the way across that metaphorical street toward the doorstep of Passive House.
This story, and many other policy successes and lessons learned, will be on offer at Passive House Northwest’s conference next week, PHnw 2020: Together We Have Time. I hope to see you there!
[Photo above comes courtesy of Wikimedia Commons.]
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