Upgrading Multifamily to Passive House principles for a 1-4% cost premium
I thought folks here would find this of interest.
David Roberts produces Volts, my favorite energy sector podcast. In this interview he speaks with with Beverly Craig, who runs the building decarbonization team at the nonprofit Massachusetts Clean Energy Center. In David’s words: “She’s been heavily involved in efforts to integrate passive house principles into the state building code and create incentives for developers of multifamily housing — especially low-income housing — to adopt passive house standards”.
Craig reports that upgrading 8 multfamily projects to those principles – when they were already at 80% construction drawings – increased costs from 1% to 4.3%. I found that both astonishing and encouraging. Would love to hear comments!
PDF of interview also attached.
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A collection of one thousand construction details organized by climate and house part
Replies
nick_vk,
I think it really depends on where you start from. Three things define what the starting point is:
- The governing building code
- The construction drawings
- The applicable experience of the contractors
The first determines what the baseline for buildings are in the region. The second two are individual to each project, and vary wildly. I suspect you might be able to stick to an increase of under 4% in the right circumstances. As a generally applicable estimate I don't think it's at all reasonable to expect.
Very good point Malcolm. My guess is that Massachusetts has more depth of experience to draw on than a lot of places. Where I live, finding a contractor or even a engineer/designer who's experienced with HRV/ERV systems is going to be a challenge. And the practices that builders are comfortable varies even within regions... in Tucson, an inch of exterior foam over exterior plywood/under stucco is standard on residential construction...in Albuquerque, it's something contractors balk at because they're not familiar with it - they are used to just stuccoing over the plywood.
Nick_vk,
I think you are right. How easy it would be right now can vary a lot. Luckily here in BC our codes have gone through three levels of energy efficiency changes in the past few years, with the eventual aim that buildings be net zero. So the drawings that were 80% complete would need very minor adjustment to get to Passive House standards, and contractors are increasingly skilled at the things that make that happen. Even here though, what that equates to in terms of an increase in construction costs I don't know. Given that the land and soft costs - consultants, permitting, etc - now constitute such a large part of the budget, maybe it's less than I think?
If you make regulations that drive up the construction costs and build on very expensive land all of a sudden 4% is a ton of money.
Still does not mean that crazy insulation value will ever save enough energy to recover their costs.
Walta
The flip side is that if land is very expensive driving up construction costs doesn't drive the final cost of housing up, it just makes the land less costly.
This is what I see in my local market, where recently I saw a house sell for $2.7 million as a tear-down. The city has gone wild with the requirements to build a house, but at the end of the day the price of that house is what the market will bear. The mandates probably add $200K onto the construction cost, but it just means that teardown isn't $2.9 million but "only" $2.7 million.
Walta,
I'm not necessarily a supporter of Passive House levels of insulation, but there are other metrics than ROI at play when we discuss energy efficiency.
Houses are durable and typically go through many owners. So it's kind of a problem that usually only the first owner gets to make decisions about how the house is built that will affect all subsequent owners. There really is a case for regulations to build houses better than would be justified solely by ROI calculations by the first owner.
I also thought that Passive House meant huge amounts of insulation, but the principles as articulated in the interview sound more like Pretty Good House principles:
1) Continuous Insulation
2) No Thermal Breaks
3) Airtight Construction
4) HIgh Performance Windows and Doors
5) Managed Ventilation with Heat Recovery
She said they've been seeing a 40-60% reduction of heating and cooling costs compared to houses built to the 2019 code. So it would be interesting to know more specifics about the standard they are building to - the article says it's model based, so you can let the modeling direct where you out the money. It sounds quite different from a Passive House design I saw a few years ago that called from pre-manufactured wall assemblies in order to achieve R-60.
Edit: After posting this, I looked it up. The answer to "what is the standard" is multifaceted. The variable is whether you want the US-based (PHIUS) or the German (PHI) standards. Going down the US Path, PHIUS's legacy (older) standard is called CORE and has both a performance standard and a limited prescriptive standard for single family homes and townhomes. It's entirely based on conservation, so it doesn't account for energy production. The newer standard is called ZERO and has similar standards but requires zero net energy consumption. To hit net zero you can offset the building's energy use with both onsite and offsite renewable energy sources. (https://www.phius.org/standards)
According to PassiveHouseAccelerator, the Phius CORE performance standards are adjusted for climate. Guessing that means you're allowed a higher net annual energy consumption if you live in Fargo or Phoenix as opposed to San Diego.