What is a Passive House?

When I first heard about Passive House (or Passivhaus as it was known when it started in Germany), it sounded too crunchy-granola even for me. My obsession with environmentally friendly design began before I was old enough to drive (I won several Arizona AIA Awards for high school energy-saving designs). Still, the story circulating in 1991 about a German physicist heating his home with a hairdryer sounded way too Burkenstocky. But when a respected colleague became Passive House certified, I started opening my mind.

I got serious in 2021 when people froze to death in their homes in Dallas after an electric grid failure. I saw reports that many people might still be alive if they lived in Passive Houses with insulation that would have kept them warm enough for several days to make it through the freeze. But the walls of their homes did not have enough insulation to keep the warm air inside even for a short time. This tragedy made me decide to become Passive House certified.

So what is a Passive House?

It’s a super-insulated and draft-free building that requires less energy to achieve a comfortable temperature. Scientist Dr. Wolfgang Feist (aka hair-dryer-guy) developed this theory, requiring rigorous testing to confirm performance. Strict and verifiable measurements make Passive House the world’s leading standard in energy-efficient construction.

A Passive House can use 85% less energy than a typical home and 50% less than current Washington State energy codes. Buildings account for 35% of total global energy consumption, so building to Passive House standards can help mitigate CO2 emissions. In addition, adding solar panels makes net-zero energy possible.

These are the fundamental principles of a Passive House:

• A continuous thermal building envelope.
• Draft free airtight layers.
• Maximizing solar gain through thoughtfully placed windows for Winter.
• Reducing solar gain during Summer.
• Reducing thermal bridging.
• Fresh air with heat transfer.

And a Passive House doesn’t need to be a single-family home; apartment buildings, college dorms, and schools can all use the energy-saving principles.

Following are answers to some questions you may have:

1. How much more does a Passive House cost?

Zack Semke, director of Seattle-based Passive House Accelerator, estimates that building to PH standards can cost 3 to 7% more than a conventional home. Investing in energy efficiency may not generate quick, short-term returns, but it offers long-term returns. With high housing costs and increasing mortgage rates, people tend to stay in place, so longer-term investments make sense.

2. What makes Passive House more expensive?

The exterior walls, roof, and floor of a Passive House have thicker insulation than required by code, so insulation costs are higher. The added inches of insulation won’t fit in a 2 X 6 wall, so the framing needs to change from what is conventionally built. In addition, windows need to meet a higher R-value than the current building code requires, and the exterior building envelope needs to be airtight to ensure that heated (or cooled) air does not leak outside. This requires planning for wall penetrations and sealing them properly. It’s not rocket science, but it does require rethinking and being more rigorous about construction. Hopefully, these practices will become standardized and become the new normal.

3. Since Passive Houses are airtight, are they stuffy?

No. A fundamental principle of Passive House design is providing optimal fresh air by using energy-efficient fans that draw used and humid air outside. Another fan brings in fresh air. The air flows are conducted past each other in a heat exchanger so that the heat of the outgoing used air can pre-heat the incoming fresh passively.

4. I’m remodeling my house, can I make it a Passive House?

Yes, but it’s going to require a more extensive retrofit to install the added inches of insulation and the airtight building envelope. There are many examples of buildings retrofitted to Passive House standards.

5. Passive House seems very technical; what if I don’t have the time or mental bandwidth to take this on for my project?

The Passive House concept is simple, but implementation is based on calculations with precise performance criteria to ensure the house meets energy-saving goals. That’s why it’s essential to work with architects and contractors that are Passive House certified. Rely on their expertise.

6. Do passive homes look odd–thinking about the Birkenstock reference–?

A Passive House can look great, but like many conventional houses, some do not. It depends on the skill of the architect. There is no need to sacrifice aesthetics for sustainability–it’s a false dichotomy.

7. Can you heat a Passive House with a hairdryer?

Kind of. Some Passive Houses can be heated with the energy equivalent of a hair dryer, but not an actual hair dryer.

8. Why is this so important to you?

Climate change news may seem like we can’t do anything to mitigate impending disaster, but I, like many others, believe we can make a difference. To challenge the doomsday narrative please join me in committing to within-my-reach sustainability goals.

For more information on Passive House design: https://naphnetwork.org/