Researchers Robert Crawford and André Stephan have just released a case study examining Passive House architecture and design, and in their conclusion, they suggest that: “if you consider the whole life cycle of a house, it turns out that sometimes a new home designed to save energy can end up using more than an average house.”
If that conclusion has you goggling, you’re not the only one. The media has picked up the story, and along the way, a lot of misinformation about Passive Houses and the study itself has spread. Here’s what you need to know about the study, why the Passive House standard is still highly sound, and what you should consider when you’re reading research, studies, and discussions about green building. Especially if you’re making big purchasing decisions about the construction or remodeling of your own home in the near future, you want to make sure those decisions are predicated by facts, not bad reporting!
Whenever you read studies on green building design (or anything else!), methodology is key. In this instance, the study is based on three case studies, using an urban apartment, a suburban Passive House, and a suburban conventional house. They looked not just at the amount of energy these buildings use over a lifetime in terms of energy demands from residents, but also energy costs locked into construction, materials, and the surrounding environment; suburban dwellers, for example, often need to drive to get to work, school, and other locales.
By comparing the three homes, the researchers found the urban apartment was actually the most efficient, and the two suburban homes were much less efficient, with results similar to each other.
These findings actually aren’t that surprising! Urban homes tend to be less energy intensive (even more so when they are built for efficiency) because of their surroundings. Urban dwellers can live without cars, relying on their own two feet, bikes, and public transit to get along. Their communities lay out everything within easy reach, making it possible to stay close to home and reduce resource use. By contrast, suburban homes are energy suckers because of the increased energy required for transport, interacting with the community, and performing tasks of daily living. Think about it: taking a subway from Brooklyn to Manhattan is more energy efficient than driving two hours to commute into San Francisco from the North Bay.
As Lloyd Alter points out at Grist, the facts behind the suburban homes are much more complicated. Suburban and rural homes in general have a higher default energy usage because of their locale. The particular Passive House chosen was large, and included expensive and resource-heavy components, which doesn’t have to be the case; such houses can vary widely in size, shape, and construction, and that can make a key difference in what’s called “embodied energy use.” Had a different Passive House been used, the results would have been very different.
“…there is no point in building a big passive house in the suburbs or the country and calling it green and sustainable, because compared to an apartment in the city, it’s not. Without even taking into account the energy required to build the roads and supply the ambulances and schools that support the lower density, in the bigger picture, the passive house is not a whole lot better than a standard one,” Alter writes.
And he’s correct. Notably, that’s also what the researchers effectively concluded in their own research: that the Passive House standard has to holistically include not just the house itself, but the energy that supplies its construction and the lifestyle of the inhabitants. Building small, dense, and smart is simply more efficient than building big, sprawled, and unwise, and it always will be. That doesn’t mean the standard is a bad idea: on the contrary, it provides great guidelines for rethinking the way we build homes and talk about energy use.
Unfortunately, this critical conclusion has been glossed over in much of the coverage of the study, which focuses on the surface conclusion, that the case study Passive House didn’t offer many advantages. This is a common problem with scientific reporting, and it’s one you can avoid by reading the original studies, and reading between the lines so you know what to look for. In this case, the case study wasn’t meant to be used as a generalizing tool, but it did provide an important reminder that we need to think carefully about the materials we choose, what we build, and where we build it.
Photo: Peter White/Flickr.