What would you think of a house with no furnace or air conditioning? It sounds very primitive, very uncomfortable. Some of us can remember when few buildings had air conditioning. But recent decades have seen the development of passive buildings.
Passive buildings have no furnace or air conditioning, but they remain comfortable without them. Some people who have lived in passive houses find conventional buildings uncomfortable.
Passive building techniques make a furnace and air conditioner unnecessary. Therefore, they require much less energy to operate.
History of passive buildings
The Arab Oil Embargo and OPEC in the 1970s raised worldwide oil prices dramatically.
Gasoline prices generated the most headlines. But the cost of heating and air conditioning drafty houses also strained American household budgets.
Research into solar power, airtight envelopes, superinsulation, high-performance windows, and energy recovery ventilation began in earnest in the US.
Engineers at the University of Illinois designed what they called the “Lo-Cal house” in 1976. It depended on heavy insulation. They projected that it would save 60% of energy consumption compared to the most efficient design from the Department of Energy. A Canadian team followed up with an even more efficient plan.
At about the same time, solar power came on the scene. William Shurcliff, a Nobel-prize winning physicist, coined the term “passive house” to describe the combination of different technologies for reducing energy use.
Then the US started to lose interest in conservation.
By that time, no one had actually built a passive house for anyone to live in. Two European scientists, Wolfgang Feist of Germany and Bo Adamson of Sweden, refined Shurcliff’s ideas. Their work resulted in the first “Passivhaus” in Darmstadt, Germany and the founding of the Passivhaus Institut there in the 1990s.
German architect Katrin Klingenberg learned about Passivhaus when she was in college. When she moved to the US, she co-founded the Passive House Institute US (PHIUS) in 2002. The US has a much wider range of climates than Germany. PHIUS quickly discovered that a single performance metric could not work in all climate zones. And unlike its German parent, it began partnerships with other organizations, including the US Department of Energy.
What is a passive building?
“Passive house” implies the design of a single-family residence. “Passive building” describes the concept more accurately.
The same basic principles can be applied to any kind of building. Besides houses, apartment complexes, offices, and commercial buildings (including skyscrapers) can be passive buildings.
Although passive building techniques usually appear in new construction, existing buildings can be retrofitted to become passive buildings.
Passive building entails five basic principles of building science:
- Continuous insulation with no thermal bridging
- Extremely airtight building envelop that prevents outdoor air from entering and indoor air from escaping
- High-performance doors and windows (typically triple-paned)
- Systems for balanced heat- and moisture-recovery, along with minimal space conditioning
- Management of sunlight to exploit it during the heating season and minimize its effects during the cooling season
Passive building techniques ensure that the building needs neither furnace nor air conditioning. They account not only for the effects of sunlight and outdoor temperatures, but also heat from occupants and appliances. Passive buildings have mechanical ventilation systems to keep air circulating and prevent unwanted moisture buildup. So they do require some outside energy. Just not for heating and cooling the air.
The heavy reliance on insulation to minimize the exchange of inside and outside air does not mean that windows and doors must remain closed. Occupants can open them at pleasure.
How does passive ventilation work?
Air gets stale in an occupied building, if only because occupants inhale oxygen and exhale carbon dioxide. Houseplants, which take in carbon dioxide and release oxygen, keep indoor air fresher longer. Changes in room temperature cause changes in relative humidity if nothing happens to control it. Excess moisture and insufficient moisture both cause various health problems.
Any ventilation system must, therefore, replace used indoor air with fresh outside air and control moisture. Outside and inside temperatures are usually different. If the outside air is cold, it will cool the indoor air when it enters. If it’s hot, it will heat the indoor air. Standard buildings use furnaces and air conditioners to regulate the temperature.
Instead, passive buildings require a heat recovery system. Various techniques exist, but basically fresh air and exhaust air pass through exchanger plates. The two air supplies do not mix. As they flow past each other in their separate channels, heat transfers between them. they become more nearly the same temperature.
A passive building costs more to build compared to a comparable conventional building. The larger the building, the smaller difference in cost, however. Not needing to pay for energy to heat and cool the building recoups the extra building costs quickly.
A passive house takes an active stand for the environment / Knight’s Energy (not dated). Link no longer works, 4/20/19
Types of insulation / Passpedia. Last modified September 1, 2015
What is passive building? / Passive House Institute US (not dated)