FAQ

The passive house standard is based on the climates of Europe. Can it be met in the more challenging climatic zones of the US?


Superinsulation, airtight envelopes, energy recovery ventilation, high performance windows, solar gain – these ideas date back decades. And many actually originated in the United States and Canada. The Europeans refined these principles for the Central European climage, where it works quite well.


In North American climates that are similar to Central Europe’s (e.g., Pacific NW), the Central European performance standard translates well. In others (parts of California, e.g.) it’s actually not stringent enough -- it’s possible to leave cost-effective energy savings unrealized and still meet the Euro-standard.


Overall, we’ve learned that in North America’s climate extremes, passive building concepts and standards require adaptation if they are to be practical, cost effective, and adopted widely enough to make a substantial difference. PHIUS is engaged in a study, based on built examples, the result of which will be climate-specific standards.



What is the difference between PHIUS and the German Passivhaus Institut (PHI)


That’s a common question and it requires a review of the history of our organizations. You can read a full treatment on that issue here.



It's common building wisdom that a house needs to "breathe." Can the passive house's air-tight construction lead to moisture or air quality problems?


This is an important issue. Many new homes today are being built tightly in an improper fashion, trapping moisture inside and leading to significant mold and indoor air quality problems.


Passive house is not immune to the risk, but there are ways to avoid problems. Passive employs an appropriate vapor barrier and then a mechanical, balanced ventilation system with heat recovery, which assures superior air-quality and comfort by continually exchanging the indoor air. Moisture is safely removed, as well as other potentially unhealthy pollutants (for example off-gassing from carpets or furniture). Also, people with allergies can easily control the indoor air-quality by specifying filters according to their particular medical needs.


Achieving this ideal, however, requires precise design and competent execution of construction details. That’s why PHIUS offers Certified Passive House Consultant Training (CPCH®), PHIUS Certified Builder Training, and PHIUS+ Rater training.


Moreover, it’s why PHIUS incorporated third-party quality assurance into its PHIUS+ project certification program. It ensures that a passive building is designed correctly, and that it has been built as designed.

 


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 or solar thermal hot water systems. 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, multifamily, schools, high-rises, and other commercial building can be design 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 tradition, Foursquare designs that fit into traditional, old 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 home owners 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 air-tight 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.   



What is a Passive House in New Mexico?

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