in pursuit of energy efficient minimalism
Could you be… The most energy efficient building, in the world???
This week, Miller|Hull presented one of their latest projects, the Bullitt Foundation’s new Cascadia Center for Sustainable Design and Construction. It’s been getting a lot of press lately, and deservedly so – it’s a progressive project shooting to meet the highly stringent Living Building Challenge. Here in the Northwest, thanks to our ample sun</snark>, the energy petal definitely poses some significant challenges. The Cascadia Center is being billed as “the most energy efficient commercial building in the world” – from a personal (and marketing) standpoint, superlatives probably aren’t the best way to try and make waves – especially if they’re not even true.
Because our region is insolation-deficient, achieving site net zero – especially on larger projects – requires some strategerie. This strategerie has definitely been a contentious issue around the Cascadia Center, culminating in a lawsuit regarding the PV array’s impact on the neighborhood and views. We’re definitely not against the use of PVs, we just don’t know if the approach undertaken here makes sense. This project does push the limits of achieving site net zero on a tight urban lot, but we feel the amount of PV is really overkill, and could possibly have been reduced by nearly a third had the project been designed as a Passivhaus.
We view Passivhaus + PV as the most efficient way to meet the energy component of the Living Building Challenge, especially here in the Northwest where the planned route is most likely going to be PV in urban settings. The Cascadia Center is aiming for an EUI (site) of 16kBTU/ft²a. Energy Usage Intensity (EUI) is defined by the DOE’s EnergyStar program as, “a unit of measurement that describes a building’s energy use. EUI represents the energy consumed by a building relative to its size.” Basically, EUI is the total energy used by the building over the course of a year, divided by gross square footage (exterior wall to exterior wall).
How does this relate to a Passivhaus commercial project?
Lucky for you, we decided to run the numbers… The published gross square footage (GSF) of the Cascadia Center is 42,773 ft²*. In order to have an apples-to-apples comparison of the as designed Cascadia Center to a Passivhaus Cascadia Center we need to find the as designed Treated Floor Area (TFA). What is TFA? TFA is the energy reference area – basically interior usable area, with deducted ratios for mechanical and circulation (60%) and stairs, elevators, chases (0%). Columns, walls, etc are also deducted. The floor plans are available on the DPD website. We pulled the pdfs through illustrator to export to DWG so we could do some basic takeoffs.
The resulting TFA is roughly 34,160ft² (roughly 80% of GSF)
As-designed annual energy usage (site):
42,773 ft² x 16 kBTU/ft²a = 684,368 kBTU/a
As-designed energy usage based on TFA:
34,160 ft² * y kBTU/ft²a = 684,368 kBTU/a
y=20.0 kBTU/ft²a
This isn’t a shabby number, but is it good enough to meet Passivhaus?
In a word, nope.
Need the proof? Let’s finish out the equation – even if the specific space heating demand can be met (and it certainly looks like it does based on the energy breakdown) the building’s specific primary energy demand has to meet the Passivhaus Standard. The specific primary energy demand calculates the building’s site energy usage by a primary (source) energy factor. For electricity, PHPP’s GEMIS primary factor for electricity is 2.7 – although in the United States, it’s about 3.0 on average (and the EIA published data showed roughly 2.84 for the Western United States in 2004, so 2.7 is probably a pretty close number)
To see if the building meets the specific primary energy demand, we multiply the energy usage by the primary energy factor…
20.0 kBTU/ft²a x 2.7 (elec primary energy factor) = 54.0 kBTU/ft²a
However, we know that passivhaus has to have a specific primary energy demand of 38kBTU/ft²a or lower. The as-designed building overshoots the Passivhaus standard by over 40%!
So let’s work backwards to see what the number should be…
38 kBTU/ft²a ÷ 2.7 (elec primary energy factor) = 14.07 kBTU/ft²a
In order for the Cascadia Center to achieve Passivhaus, it would have to reduce its primary demand fairly significantly. Again, the maths…
34,160ft² x 14.07 kBTU/ft²a = 480,631 kBTU/a (site)
To find the EUI, divide the annual usage by GSF:
480,631 kBTU/a (site) ÷ 42,773 ft² = 11.24kBTU/ft²a
In order to meet the Passivhaus standard, the EUI for Cascadia Center would have to be 11.24, not 16.
This means that if the Cascadia Center were to achieve Passivhaus (which, conceivably, they’re probably close to achieving), they would only require 70% (11.24/16) of the PV area to meet 100% site energy. Or, alternately, with the as-designed PV array, they could be at or near carbon neutral (which is the goal of the 2030 Challenge).
This is the leap where Passivhaus makes the most sense to us – the savings are significant long before throwing up a PV array, so we’re always a little confused when developers of commercial projects (or schools, libraries, fire stations, etc) opt to not put a little effort into making the building actually energy efficient.
So back to the superlative… If this is the “most energy efficient commercial building in the world“, why can’t it meet the Passivhaus standard? And if there already are commercial buildings that meet the Passivhaus standard, wouldn’t these all be more energy efficient than the Cascadia Center?
Our answer is a definitive yes.
Projects like the e-trium and the Marche International Headquarters both meet the Passivhaus standard. Marche even has enough PV to be site net zero, which strangely means not only is it more energy efficient than the Cascadia Center, but it required less PV to be site net zero…
So that’s our back of the napkin math on this project… If you’ve any comments/critiques/etc you know where to leave them!
*Even if our numbers are off, as long as TFA is roughly +80% of GSF (which is pretty typical), this premise will still hold true.
Additional Reading
- Miller|Hull Nov 2010 DPD design review presentation (PDF)
7 Comments
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Without ever running the numbers (thanks for doing so BTW), I came to the same conclusion when I saw a rendering of the truly massive PV array this project will sport. Improving the EUI (both through better envelope and reduced internal loads) is clearly preferable.
But even a 30% smaller PV array will be huge and I dare say will not soon become a common feature on similar projects, at least those that have more typical budgets. This calls into question the wisdom of Living Building’s central approach. Given that we already have cities, and we are promoting them as the most environmentally responsible place to put ourselves and our stuff, and it’s neither affordable or sustainable to dismantle, move or rebuild all their structures en masse, is it really a reasonable solution for every building to be self contained with regard to energy, water and waste? Isn’t one of the very reasons that cities perform well is that we can share infrastructure and resources? Isn’t a steam plant or sewage treatment facility more efficient (space, energy, materials) and easier to upgrade than each structure having it’s own?
Living Building is admirable for being comprehensive and inclusive, but I wonder if looking at each building site as a closed system actually subverts the big picture perspective it’s trying to achieve, and in doing so renders it a boutique standard which might generate moon landing technologies but not railroad impact.
Comment by Geoff Briggs — May 7, 2011
Geoff,
Yep, a 30% smaller array is still enormous. I’m still not quite sure how it fits within the human scale/beauty petals to slap an over sized array on the building.
The question of removing buildings from existing infrastructure or not connecting new ones is important – we’ve definitely struggled with the implications, especially on a social justice level. If every new building in the city of Seattle were to be a Living Building – completely disconnected from the grid and sewer, the burden of maintaining that infrastructure increasingly falls on those that can’t afford to disconnect from the existing systems. That’s not equitable on any level.
Furthermore, how big is the array, 220kW? The last system I saw that was that large was about $5.00/watt for PV, installation, array, consultant fees, etc, so roughly $1,100,000.
At 600 grams of CO2 per kWh, the 264,000kWh array will produce 174.6 tons of CO2/year. If carbon offsets on the higher end are about $30/ton, you’re only looking at paying $5,238 to offset CO2 emissions. A bigger “bang for the buck/social justice” aspect would be to seal up 2,750 homes at $400 each.
The environmental and economic savings from that would significantly outweigh one building being site net zero.
Comment by mike eliason — May 7, 2011
Great analysis guys, and an important discussion as we see the scale of these uber green buildings growing. Portland is also in the midst of planning it’s own urban Living Building, the Oregon Sustainability Institute. I would love to see a similar calculation for the OSC.
No mention of passivhaus (or even any data about performance or EUI) but they do tell us “The cornerstone of OSC’s energy plan is the array of photovoltaic cells that will blanket the building.” Unfortunately the architecture is suffocating a bit from the weight of the giant PV blanket.
Regarding shared infrastructure, the OSC is at least being planned as the nucleus of a future Portland State ecodistrict.
Comment by jeff stern — May 9, 2011
Jeff,
We’re also familiar with the OSC building – which also has some aggressive goals, especially due to the scale. I saw early EUI goals of 18-20 kBTU/ft2a. At 18kBTU/ft2a, meeting Passivhaus would appear to require only (11.5/18) 64% of the PV area. With over 60,000 sf of PV on OSC, meeting Passivhaus means elimination of PV on canopies and integrated w/ façade is possible.
Another thing Passivhaus has over both the Cascadia Center and OSC is that the planned LBCs will require occupants to ‘adjust temperature expectations’, whereas Passivhaus shouldn’t require such expectations.
In discussions we’ve had, another important topic is reliance on laptops instead of desktops, or ‘alternative computing strategies’ – does this mean people will be expected to take their laptops home to be charged? If so, this is a horrible strategy – deflating the building’s actual EUI by decentralization is really a method of punting on the hard part of meeting the LBC. It also means a very false EUI – the building’s actual energy usage would be much worse – net metering just wouldn’t reflect this. We would call this ‘creative accounting’.
Comment by mike eliason — May 9, 2011
Mile, et al,
thanks for the reply. The social justice aspect of disconnected “rich” buildings is an angle I hadn’t considered. It’s like private school families voting against school levies, and SUV commuters voting against transit funding. I’ve got mine, screw you.
OTOH, I don’t think the laptop incentive is creative accounting. Those computers are just more efficient and I think cooler. (Some desktops, like iMacs might be equal). Another factor is reduced need for back-up power supplies. Lastly, if portables are most people’s primary computer it lessens the need for a work laptop in addition to a desktop, and for some users eliminates the need for a home computer.
Comment by Geoff Briggs — May 10, 2011
Good analysis but I do wish we could all agree to separate evaluation of buildings from generation of electricity on the roof. Great that people are investing in renewable energy generation but why link it to the building?
Fine if PV is seen as cost effective, building is somewhere sunny, roof is available and facing the right way without shading, and you can afford it, and dont have greener things t do with the money, etc but that is a lot of boxes that are not generally ticked for so called zero carbon buildings in UK.
I have shown elsewhere how adding a gas boiler (for example) to a grid linked electric solar building will increase building emissions but reduce global emissions by saving 3 units of gas at the power station for every unit of gas replacing electricity for heat. Yes there are buildings with electric space and water heating and PV.
This is why PH doesn’t reward PV in the same way as all this zero carbon/energy nonsense.
Nick
Comment by Nick Grant — May 11, 2011
It seems that we Americans–including our governmental and other institutions– have lost the core value of conservation. Instead we have become addicted to high-tech solutions that feed the same demand for energy through expensive renewables.
Not only are the technical arguments above right on, but the socio-economic ones as well. As the United States continues to fall behind other nations in innovation, fairly distributed wealth, education and other fields, fewer and fewer people and institutions will be able to afford the basics, and certainly not “rich” buildings.
Poverty and the lost opportunity costs of expensive renewables are great motivators for energy conservation. It’s a message people with no math or science skills can understand, and one we Passivehaus advocates should promote.
Comment by Joseph Balachowski — May 18, 2011