The Genesis of LEED and Passive House
Fast forward a few decades and two more homes that we remodeled extensively, each time beefing up the insulation and replacing windows and doors. Regrettably, triple pane windows were no longer available, as manufacturers had instead moved to gas filled, low-e iterations.
Our desire to design and build a home just the way we wanted rather than fixing someones else’s house continued to grow. Fueled by years of subscriptions to magazines such as Fine Homebuilding, Journal of Light Construction, This Old House, and Solar Today, we set about defining what we wanted. If anything, my desire for better energy performance continued to blossom.
There are many green building standards. Clearly defined and validated standards are very important nowadays when all to many manufacturers and builders seem to be more a green facade. An article in the Dec 09/Jan 10 issue of Fine Homebuilding article described the options. There’s the US Environmental Protection Agency’s Energy Star for Homes; the National Association of Home Builders National Green Building Standard (NGBS); Masco Corporation Advanced Energy Corporation’s Environments for Living, along with many local and regional ones. Perhaps the most prominent national standard is the U.S. Building Council’s Leadership in Energy and Environmental Design (LEED). I was familiar with LEED: while working for the Department of Navy, I helped to institutionalize a new policy, the first within the Department of Defense, that all new Navy and Marine Corps facilities would be built to the LEED Silver standard. I liked the way LEED cut a wide swath across many aspects of green building, including site selection, water conservation, sustainable materials, along with energy. Curiously, the article did not mention, nor was I aware at the time, the Passive House standard. Back then, we decided that when the time came, we would find an architect to design and a builder to construct our new home to the LEED Platinum standard.
I don’t recall exactly how I stumbled onto the Passive House standard last year, but I quickly recognized its value. While I still liked the broad mandate of LEED compliance, I also came to see it as a limitation regarding the energy component. I bought the book Homes for a Changing Environment published by the US Passive House Institute. I really liked how Passive House was exclusively focused on building an extremely tight shell, that there were only three very specific, objective criteria – a heating/cooling load, a total energy load, and a post construction air tightness test. The first two are based on a proprietary Passive House model that considers a multitude of home designs and local site environmental criteria. You know before construction begins whether or not the house will meet two of the three Passive House criteria.
Ah, but there’s the third factor……the post construction blower door test. Laying the foundation, erecting the walls and roofing, sheathing, hanging drywall, installing the plumbing, electrical, insulation, and outfitting it with all the mechanical, electric and electronic components is a huge and complex undertaking. Sure, each of the mechanical/electric components are individually tested prior to use, but doing a blower test to check the air tightness of the building envelop was something I’d just recently read about in the Jan 2010 issue of Journal of Light Construction. A light went on my my mind: model predictions are fine, and promises on energy performance are great, but where’s the guarantee? How do you know that a great energy design, confirmed by a well recognized energy load model, coupled with top flight materials and a recognized builder, will combine to achieve the desired energy performance unless you test the performance after construction is completed. Since Passive House certification is a pass or fail test for all three factors, you’d better conduct one or more initial blower door tests as intermediate steps to ensure that the entire building assembly is on track for the final pass or fail exam. Well doesn’t that make sense!
I have now read many articles about the Passive House standard. Each has noted that meeting the criteria is attainable but very challenging. There is absolutely a learning curve for not only the framers, but nearly all of the trades who work on the house. Attentional to construction details are critical, particularly regarding air sealing and thermal bridging. I liked that. While I was inspired by Homes for a Changing Environment; it offered virtually no details on how to actually build the house. After all the remodeling we’d done, I wondered about the technical construction details. Fortunately, there have been a number of articles in the last year in Fine Homebuilding and Journal of Light Construction on various ways to attain Passive House-like performance. And I have also read that LEED is now exploring a post-construction energy performance test for possible inclusion in a future LEED standard.
We decided that we would build our house to both Passive House AND LEED standards. If finances or other events forced us to choose one, we’d pick Passive House.