Harrison Architects

Passive House

No Mention of Passive House in Seattle Climate Action Plan and Nick Licata Resolution 31400


Neither the City of Seattle Climate Action Plan to achieve carbon neutrality by 2050, nor Nick Licata's Resolution 31400, establishing a Green Building Advisory Board for the City of Seattle, make any mention of Passive House.

Passive House (Passivhaus) is the approach to designing ultra-low-energy residential, commercial and institutional buildings that reduces energy used in heating and cooling to 10% of code, and total energy use to 30% of typical. In Europe it is widely supported by governments and widely implemented (in 37,000+ buildings!)--all for costs comparable to conventional construction.

To leave out this proven, cost-effective means of achieving our carbon reduction goals seems like a serious and unfortunate oversight, perhaps brought on by the fact that at the time the Climate Action Plan was being developed, the Green Ribbon Commission (the group tasked with developing the Action Plan) did not include anyone with Passivhaus knowledge or experience. Passive House is relatively new on the scene, with only several built examples within City limits, but a forward-thinking city should look to forward-thinking solutions.

I am confident that any number of the members of Passive House Northwest could provide the expertise neccessary to add Passive House to the mix. 


Brussels' Exemplary Buildings Program


Yesterday's Passive House Northwest Annual Conference was fantastic, led off by a rousing keynote on Seattle's greenest building to date, the Bullitt Center, by Denis Hayes. The theme for the conference was "Building Bridges." That means reaching out to our community of like-minded adventurers on the edges of low energy architecture--the International Living Future Institute (ILBI), the International Passive House Institute (PHI), and the Passive House Institute US (PHIUS), as well as all of their various supporting and affiliated organizations. At the core our values are the same and it's time to set aside minor quibbles and work together.

At the conference, 200 of us heard from Joke <"Yoka"> Dockx, of the Brussels Institute for Management of the Environment. She is responsible for the Exemplary Buildings program that over the last five years has encouraged and incentivized the creation of over three million square feet of low-energy buildings in the 62 square mile region. 53% (over 1.5 million square feet) of those buildings are Passivhaus buildings.

After the success of the program over the last five years, Brussels has resolved that as of January 1, 2015, all new public and private housing, schools and office buildings in the Brussels region will be required to be built to the Passivhaus standard.

In a nutshell (as I recall): 75% of energy use in the Brussels region is associated with buildings. (Lower transportation energy than Seattle....) Every year since 2008 they had an architectural competition for net-zero and low-energy buildings. The winners were all given technical assistance, publicity, and a financial award amounting to $12 per square foot, 90% of which went to the building owners, and 10% to the design team. The program cost was (I believe) $37 million per year. The results have been that total energy use in the region has been reduced by 10% since the start of the program. Results going forward, when the requirement for Passivhaus kicks in, will be even more dramatic.

Here is the program description for 2012 (translate with Google...): http://www.bruxellesenvironnement.be/uploadedFiles/Contenu_du_site/News/FR_BATEX%202012_reglement_DEF_120221.pdf

Anywhere in Western Europe has the benefit of 20 years of Passive House experience--37,000 Passivhaus buildings, mainly in Austria and Germany. But I found Joke's presentation charming and compelling, and I'd like to suggest that we bring her back to this area to talk to City Council and the Mayor, King County Council and Puget Sound Regional Council, to understand how Seattle and King County and other local jurisdictions might move in this direction.


The Greenest Building: Retrofit or Passive House?


Yesterday, preservation rock-stars Preservation Green Lab released the results of a study on the energy impacts of retrofitting existing buildings versus building new ones. Their unsurprising--for an arm of the National Trust for Historic Preservation--conclusion: Retrofits are almost always greener than new buildings. Building Green picked up the story, as did Grist.

But...are the assumptions of the study biasing it toward that conclusion?

I know several folks at Preservation Green Lab (they are here in Seattle), and they are super-smart, committed people (smarter than me, no doubt.) Still, I'm skeptical of their conclusions. The stated assumption of 30% energy savings (for the advanced case!) is a very low bar. How would the results differ if in both cases the new and retrofitted buildings achieved Passivhaus, saving 90% of their heating/cooling energy instead of 30%? What if we compare retrofitting an existing building to Passivhaus standard with building a new one, also to Passivhaus standard? Or, the most likely real-world example, compare retrofitting an existing building to achieve a 30% energy savings (if that's as far as it could feasibly get) to building a new Passivhaus building with 90% savings (that could be built for the same cost)? How would those scenarios pencil out, comparing Return-On-Investment? We already know its harder to get to Passivhaus with a retrofit. What if required zoning setbacks or fire ratings of materials prevent adding exterior insulation to the existing building, making achieving Passivhaus difficult or impossible, such that the only way to get to Passivhaus (get to 90% reduction, that is) would be to build new? 

David Roberts (another smart Seattlite) laid out "the brutal logic of climate change" in a Grist post. (Required reading!) The Architecture 2030 Challenge, rightfully, has set out goals for the reduction of energy use in buildings that start with a 60% reduction today. Why are we even discussing 30% reductions?  As I said in my interview in The Atlantic, "The economic and social costs of climate change will be increasingly, staggeringly huge, and the longer we wait to begin [serious efforts at mitigation] the fewer resources we will have to work with..." As I tweeted last year, buildings built now to current codes will be worth less in 20 years--they are already obsolete.

The problem with new buildings is not that they are new, but that they are poorly designed. They are poorly designed in part because the means of financing new buildings favors large developments that max out the zoning envelope, rather than the finer grain, smaller buildings more often found in the kinds of existing neighborhoods we all love, and that will create the kinds of vibrant, transit-oriented, walkable dense urbanity we need to meet our carbon emissions goals. We need to think as hard about how to change the means of financing construction as how to build buildings that use less energy. Second, buildings are poorly designed because they don't go far enough in their energy intelligence. They stop at the point they're expensive enough to discourage their owners, rather than pushing harder and farther to get real savings. With Passive House we have to tools to reduce primary energy use by an average of 70% (depending on building type). Let's start the discussion there, eh?

There are excellent reasons for keeping existing buildings: embodied memory, sense of place, appropriate scale.... I'm just not convinced saving energy is the unequivocal answer to the question of new versus remodel that this study suggests.

I'm looking forward to reading the report in detail, before I put my foot further in my mouth than I already probably have. After I get a chance to do that, I'll update this blog entry to reflect my conclusions.

UPDATE January 30th.

I've had a chance to read through the entire study, and have a couple additional comments. From the study:

This groundbreaking study concludes that building reuse almost always offers environmental savings over demolition and new construction. Moreover, it can take between 10 and 80 years for a new, energy-efficient building to overcome, through more efficient  operations, the negative climate change impacts that were created during the construction process.

I don't know about you, but I'd guess some would be tempted to read that and say "Well, dang, we better not build anything new then, eh? That so-called "energy efficiency" stuff is just more liberal hogwash!"

The all-caps "key finding" of the study is:


The footnote is: 

"2. where energy performance for renovated and new buildings is assumed to be the same."

Well (forgive me)...duh! If operating energy is the same for both new and retrofitted buildings, the only difference in total energy use is the embodied energy saved by reusing the existing building. Of course it's going to "save energy" to use an existing building if you look through that lens.

The other issue is that an existing building (unless it is a single family house) will almost never replaced by a building of the same size and functionality. A one-story building in an urban village, for example, is not going to be replaced by another one story retail building, but by a five-story ("four-over-one") apartment or condo over retail mixed use building, which also increases density, saving energy, and which makes transit feasible, again saving more energy. Liz Dunn's own stunning Agnes Lofts project is a beautiful example of that kind of urban succession.

The authors do acknowledge that the study did not take those effects into account, but that doesn't seem to have diminished the enthusiasm with which the press has embraced this study and repeated it's "key finding." 


Passivhaus Could Have Made Bullitt Foundation LivingBuilding More Energy Intelligent


If the Bullitt Foundation's Cascadia Center Living Building had been designed to meet Passivhaus, it would have needed only two-thirds of the on-site-generated energy of the current design to reach net-zero. In other words, a much smaller photovoltaic array.

Denis Hayes has long been a hero of mine. In ninth grade I participated in the first Earth Day, and that day in some ways catalyzed the direction I took with my life. I met Denis briefly at Worldchanging's Future City event, mentioned Passivhaus, and was surprised to learn he was unfamiliar with the approach. We later agreed to get together to talk about Passivhaus over lunch. Last October, sitting across the table from him at a small restaurant not far from the Bullitt Foundation's headquarters on First Hill in Seattle was a real thrill. I shared my knowledge of Passivhaus. We talked about the Cascadia Center. At that point, the design for the building was set, and I had no illusions (ok, few illusions...) about influencing the design. I was curious about how Cascadia Center might compare with Passivhaus, in terms of its energy intelligence.

The Cascadia Center for Sustainable Design and Construction (website for the building) is likely to be the second building in Seattle to meet the Cascadia Green Building Council's rigorous Living Building Challenge. I wrote about the Living Building Challenge on this blog when it was first announced in 2006. It is the first green building rating system that makes complete sense to me. It represents exactly what we should be doing with our buildings. I feel so strongly about it that (as with Passivhaus) I offer a discount on my fee to clients whose projects meet the Challenge. (No one has taken me up on it yet.) Designed by Seattle starchitects Miller|Hull, with mechanical engineering by Portland's PAE Consulting Engineers with input from the Integrated Design Lab, the building is a marvel of sophisticated active technology and expressed greenness. Motorized windows open automatically to provide cooling. Computer-controlled sun shades raise and lower to help maintain optimum lighting levels. Deep borings below the building tap geothermal warmth. A prominent stair with spectacular views encourages tenants to skip the elevators. There is no parking garage! (But there is bicycle parking!) A (very) large, controversial photovoltaic "hat" tops the building. (Some call a previous larger version the "comb-over.") The Bullitt Foundation expects it to be the most energy-efficient commercial building in the world.

But will it be?

After the public presentation of the building at Benaroya Hall I emailed Scott Wolf of Miller|Hull and Denis Hayes, asking if I might have information on the building necessary to make a comparison with Passivhaus. Denis responded that he would be delighted to cooperate, and Scott put me in touch with Brian Court, the project architect, and Jim Hanford, sustainability lead, both of Miller|Hull. I am grateful to each of them for facilitating this conversation and supplying the area take-offs and EUI for the current design. Before we get into the numbers, if you haven't already read it, you might want to click over to my introduction to Passivhaus and back.

  • The gross square footage of the building is 52,000 SF.
  • The current Energy Use Index (EUI) is 16.
  • The Treated Floor Area (TFA) based on the German DIN 277-2 method is 39,050 SF. A relic of its German heritage, this number is used in calculating energy use in Passivhaus.
  • The limit in Passivhaus for Primary Energy is 38 kBTU/SF of Treated Floor Area/year. "Primary Energy" = "Source Energy."
  • In Passivhaus, an "energy factor" is applied to various forms of energy to account for generation and transmission losses. For electricity, this factor is 2.7.

Solving for an EUI that would meet Passivhaus

38 kBTU/SF/yr ÷ 2.7 = 14.07 kBTU/SF/yr. (Dividing our Passivhaus allowable energy target by the energy factor gives us an annual Primary Energy usage target taking the electrical energy factor into account.)

39,050 SF (TFA) x 14.07 = 549,434 kBTU/SF/yr (This gives us the allowable total for Passivhaus for the total annual source energy usage using TFA.)

549,434 kBTU/SF/yr ÷ 52,000 (GSF) = 10.57 (This gives us the EUI target for a building of that would meet Passivhaus.)

10.57 ÷ 16 = .66

A building that met Passivhaus would use 66% of the energy of the Cascadia Center as currently designed.

Or, looking at it the other way:

52,000 GSF x 16 (current EUI) = 832,000 kBTU/yr (total annual Primary Energy usage)

Solve for kBTU/SF/yr using TFA.

832,000 kBTU/yr ÷ 39,050 SF (TFA) = 21.3 kBTU/SF/yr

Multiply that by 2.7 (the energy factor for electricity) to get the primary energy usage. 

21.3 kBTU/SF/yr x 2.7 = 57.52 kBTU/SF/yr

Passivhaus requires an annual primary energy usage (source energy) of 38 kBTU/SF/yr.

The building as designed exceeds the Passivhaus standard for Primary Energy by a bit over 50%. That's even worse than my Passivhaus colleague Mike Eliason of brute force collaborative calculated using guesstimates of TFA from the permit documents filed with DPD.

Since there are commercial office buildings already built in Europe that meet the Passivhaus standard, it appears the Cascadia Center will not be the most energy efficient building in the world.

It is unlikely the building could get to Passivhaus from where it is now. Like many green building strategies, Passivhaus is very difficult to implement successfully after Schematic Design is finished. (I've tried!) We do know Passivhaus can be reached in this building type, because there are examples of similar buildings in Europe that meet Passivhaus, all of which would have a lower EUI than Cascadia Center if you don't count the PV.

I suspect we may see something interesting if we can compare the Cascadia team's air leakage target of 0.25 cfm/SF @ 75 Pascal with Passivhaus's 0.6 ACH@50 Pascal. (The calculation is not trivial.) Proportionally the ventilation and pump energies seem high, but once all other loads are reduced, those loads might pop out more, and pumping is required for the reuse of water in the building, a requirement of the Living Building Challenge. If they were starting from scratch, it may be that by starting first with siting and building massing, then optimizing envelope assemblies and air-tightness (as we do in the Passivhaus design process) they would be able to eliminate the need for some of the mechanical systems. With the internal heat gain of a typical office building, and an appropriate wall assembly, air tightness and glazing, heating load ought to go to zero, and with proper shading (as they've done) cooling load should get to close to zero as well.

Ironically the featured stair, intended to encourage walking over using the elevator, contributes to the building missing the Passivhaus mark. As circulation space, it is not counted in the Treated Floor Area, so has the effect of reducing the total kBTU available for use annually while still meeting Passivhaus.

Despite not meeting Passivhaus, Cacadia Center is a brilliant, important building. That it will be possible to better it, with simpler, less expensive and more durable technology is encouraging. Since we already see dramatically lower energy use with existing Passivhaus buildings, it seems clear that Passivhaus is a better way to meet the "Energy Petal" of the Living Building Challenge than the active technologies employed in the design of the Cascadia Center.

In the United States no one has yet built a commercial or institutional Passivhaus building. Who's going to do it first? We are available to help.

The Chainsaw Retrofit


The Passivhaus approach can be implemented when retrofitting existing buildings as well as when building new ones. Heating energy use in an existing building can be reduced to 10% of what it was prior to renovation. There are (of course) a number of challenges. In western Washington, achieving Passivhaus in an existing building will require:

  1. Adding additional insulation in walls, roofs and floors.
  2. Replacing windows.
  3. Improving air tightness.
  4. Installing a balanced heat recovery ventilation system.

Clearly this is not a trivial or inexpensive undertaking. However, when a planned renovation will involve new siding, windows, and furnace anyway, it is worthwhile investigating an upgrade to Passivhaus performance. Let's say like many of our clients you are interested in having a ground source heat pump as your source of heat. In one of our projects, we found that by going to Passivhaus we could obviate the need for the ground source heat pump altogether, so we could save that money, and use it to pay for much of the cost of the additional insulation and better quality windows. It will still cost more (10%-20%) to get to Passivhaus, but the investment you make in the envelope of your house will pay dividends for the life of the structure.

The "chainsaw retrofit"--so called because this approach involves removing the overhangs of the existing house with a chainsaw!--is one way to add the additional insulation. Matt Wasse in our office has created an animation to illustrate how this approach works. Have a look: 

Try http://www.flickr.com/photos/robharrison/5337590411/ if you have trouble playing the video.

Sightline: "Getting Aggressive About Passive House"


Roger Valdez of Sightline Institute writes about Passive House in a blog post titled "Getting Aggressive About Passive House." The post mentions me and my Passive House Consultant Training classmate and friend Jim Burton of Blip Design.


Worldchanging: Sustainability Gap - Passive House in America vs Europe


Alex Steffen of Worldchanging.com picks up and comments on today's New York Times article on a new Passive House in Vermont:


The New York Times article is quite good, and includes a video and interactive feature on the secrets of Passive House.

Good stuff!


Farm + Forest House


Farm and Forest Passive House
I have posted a new page on the Farm + Forest House in the Projects section of our website.

We received approval from Pierce County for this house, designed and detailed as a Passive House, on June 30th. It would have been the second permitted Passive House in Washington State. Alas, the Passive House component of the project has been removed.


Passive House now on Wikipedia


For a quick look into Passive House (Passivhaus in German) criteria and design strategies, take a look at Passive House on Wikipedia, the free Encyclopedia. The article has diagrams, a history of Passive House and the standards for creating a building that requires 1 BTU/square foot/degree day.

Passive House buildings use 75% - 95% less energy for space heating and cooling than new buildings that meet current US energy efficiency codes. This summer Rob and Matt both took the Passive House Consultant Training course. We are excited to put these standards into practice.


Solar Decathlon Shows Passivhaus Standards are #1 for Energy


Solar Decathlon is a worldwide competition that annually challenges groups of students to design, build  and operate the most attractive, effective, and energy-efficient solar-powered house. This year's 1st and 2nd place winners (Technische Universität Darmstadt and the University of Illinois at Urbana Champaign, respectively) modeled their designs off of Passivhaus standards.

We are enthusiastic about the successful examples of Passivhaus, as we are currently working with those standards on projects of our own.

Richard Defendorf of GreenBuildingAdvisor.com blogs about the winners at:


Passive House (Passivhaus) in the Northwest


I have just completed the first of three 3-day sessions of the Passive House Consultant Training. It was a compelling introduction to the principles and techniques of this approach to radically reducing the energy used in buildings--to the point that the house can be heated with the equivalent of a hair dryer! We are going to use this approach with two of our current projects, and hope to incorporate this into all of our projects going forward. Here are a few highlights:

• Typically when we design energy-efficient houses, we start with our more or less standard (to us) approach to the envelope of the house, and then size the mechanical system to suit the heat loss of the envelope. With Passive House approach, it's the other way around: we start with a fixed amount of energy that can be used for heating, cooling, lighting and plug loads (4.75 kBtu/SF/year), and design the envelope to make that work.

• Insulation varies with the climate, but in Seattle will likely be in the range of R-60 for walls, ceilings and slabs. Walls will be about a foot thick, offering lots of potential for design of the exteriors.

• The detailing of the ways wall, floor and slab meet each other will be different, primarily to eliminate thermal bridges.

• The houses will be very tightly constructed. Air infiltration and leakage will be less than 0.6 ACH@50 (air changes per hour at 50 Pascals. Typical construction is the range of five or six ACH@50.

• In the heating season, lots of fresh air will be supplied by a heat recovery ventilator.

• Windows and doors with a U-value of 0.09 will probably be imported from Germany. There are currently no manufacturers in the United States making windows or doors that qualify, though Serious Windows does come close.

• We will optimize passive-solar and internal heat gains. At this level of efficiency, the warmth generated by the refrigerator (and other appliances) must be accounted for! This also means careful study of shading, to prevent over-heating. Interestingly, the Passive House will not have a huge bank of south-facing windows, and no windows elsewhere, like the stereotypical "passive solar" house.

• We will be modeling the energy gains and losses using a program called the Passive House Planning Package, a sophisticated Excel-based spreadsheet.

• Sometimes referred to with its German spelling, Passivhaus, to distinguish it from "passive solar" houses.

• Inspired by work in the United States, but developed in Germany. So far there are only a dozen or so Passive Houses built in the US, but over 10,000 in Europe.

More on this later!