A Different Approach to Building Science


How does the cost of Passive House construction compare to that of standard building?

It can vary by climate and project, of course, but a good rule of thumb is this: To achieve Passive House standard requires an additional upfront investment of approximately 10% of the construction budget, as compared to regular energy code-compliant 2x4 construction.

Why the name "Passive" House?

The “passive” in “Passive House refers to achieving overall energy savings of 60-70% and 90% of space heating without applying expensive "active" technologies like photovoltaics. Energy losses are minimized, and gains are maximized. Superinsulation and air-tight construction minimize losses. The heat/energy recovery ventilator helps keep energy that has already been generated in the house instead of venting it out. Knowing about thermal storage capacity of certain materials and their "passive" effects on the indoor temperature of a home, the architect/designer can plan for enough thermal storage mass in a house by specifying tile floors, finished concrete slabs, concrete or granite countertops, stone fireplace surrounds, adobe walls or earthen plaster.

Of course, photovoltaics, solar water heaters and other technologies can still be implemented. In fact, passive has been recognized by the U.S. DOE’s Challenge Home program as the best path toward Net Zero or Net Positive homes.

The “house” part of Passive House is an unfortunate misnomer leftover from the German name. In fact, all kinds of buildings -- single family, multi-family, schools, high-rises, and other commercial buildings can be designed and built to passive standards.

One other thing: Passive House refers to energy performance, not an esthetic. Here in the United States, successful Passive House designs range from sleek, contemporary town houses to traditional, Foursquare designs that fit into old, historic neighborhoods.

Can you open the windows of a Passive House?

Yes! You can open windows and live in a Passive House just like in any other house. It is a normal house. You have the tools to do just what you would do in any other house: if it is cold outside, instead of sending the warm air directly outside through opening your windows, one can use the ventilator to do the ventilation, keeping the heat inside the house (some "old world" people insist on sleeping with open windows no matter how cold it is outside. Studies have shown that cracking a window at night during winter has no significant effect on the performance of a Passive House. It still works!).

During the in-between seasons one can bring in fresh air through windows like in any other house, and even turn off the ventilator if so desired. If it is hot outside, it's best to keep the hot air outside and the cold air generated through active cooling or night cooling in. The ventilator then recovers the cold air for you and you still are able to properly ventilate your home.

Note that studies have shown that most people do not ventilate their home as they should. The desired humidity inside a home should be between 30-60%. If it is lower than 30% most people perceive it as uncomfortable to breathe. If it is above 60% mold growth will be supported and is very likely. Regular homeowners should open their windows every two hours for two minutes to ventilate properly (including night hours). The Passive House provides proper ventilation continuously, at low speeds and free of dust; creating a superior, healthy indoor air quality.

Is radon a problem in Passive Houses?

Radon is a radioactive gas that can come into a house through the ground, primarily through cracks in basement walls or concrete slabs. Because Passive Houses are built to such a high airtight standard, the entry of radon is prevented as best as is possible. Beyond that, any possible infiltration is met by a balanced ventilation system that continuously refreshes the indoor air. Passive Houses are, by design, well protected from the dangers of radon.