Passive House Standards - 90% Less Heating Energy: Guest Blog
Lauren from New Ecology joins us to talk about a building concept known as Passive House.
Want a building that uses 90% less heating energy than typical code construction?
It’s not easy, but it is possible. In fact, it is somewhat common in places like Germany and Austria, and there are a number of climate-inspired enthusiasts that are making it happen right here on American soil.
The program is called Passive House, and in simple terms it is a building that is modeled and certified to meet the following performance characteristics:
Annual heating requirement less than or equal to 4.75 kBTU/sf/yr
Primary energy use less than or equal to 38.1 kBtu/sf/yr
Airtight building shell that achieves a .6 ACH @50 pascal pressure or less
Sounds pretty easy, right? Well, not quite. This deceptively simple set of requirements for compliance are some of the toughest performance standards on the market. If you live in climate zone 5, like me, it means that you are designing and constructing a building that is super-insulated and thermal bridge free (think R-40 walls and triple pane windows), providing all of the building’s ventilation and a significant chunk of its heating demand through very high efficiency energy recovery ventilation, and using the natural heating energy of the sun to warm the building in the winter (don’t forget to shade that exposure in the summer to reduce overheating potential). Many also incorporate a solar thermal system to heat the domestic hot water, and all are meeting the most stringent thresholds for air tightness. At the end of the day, most Passive Homes do not need what you would consider to be a typical mechanical system, many just use very minimal point source heating/cooling to cap off what is not provided by the ventilator or the sun. In my perspective, this system outshines other green building rating systems in its ability to push designers to think holistically about their building and really analyze their design decisions in terms of ramifications on performance.
If you happen to live in San Francisco or Seattle, you’re in luck! Not very much of a heating or cooling load there, so you are likely going to be able to get your new construction project to the Passive House standard with less beefy walls and windows. Retrofitting a building? Building a school? You can be Passive House certified as well – the program has separate standards specific to the unique challenges of rehab and non-residential buildings.
While most of the certified Passive House buildings in the United States are single family homes, there are a significant number of developers in Europe and a few in the US that are using this standard in the construction of multifamily properties. In fact, there is an affordable multi-family passive house project currently in the works in Bushwick, Brooklyn by the always pioneering design duo at Architecture and Energy Limited, Chris Benedict and Henry Gifford. This project is slated to be the first large apartment building to meet the Passive House standard in NYC, and should be starting construction this year.
While it does cost more to build a Passive House, advocates and veterans tout data that estimates the incremental cost to approximately 10%. This is surprisingly small considering how efficient these buildings are. The idea is that there are significant economies available to the project if you don’t need a typical mechanical plant and distribution system, economies that can then be put into the extra cost associated with the building envelope.
I’m really looking forward to this program gaining more traction in the US, especially in the multifamily arena. More projects means more juicy data that helps us better define the real costs and energy and carbon footprint benefits of Passive Homes of all shapes and sizes.