Passive building strategies use elements like a building’s location, the local climate, and materials as natural opportunities to save energy on heating and cooling systems and keep operational costs down. They can help reduce front-end costs, as well as emissions related to heating, cooling, and lighting. Passive House, or PassivHaus, is a building standard based on a set of core passive design principles. First, Passive Houses must use continuous insulation in the entire building envelope, which is completely airtight. They must have high performance windows and doors that manage solar gain, absorbing heat when it’s cold out and minimizing overheating when the weather is warm. Passive Houses use some form of balanced heat- and moisture-recovery ventilation and a minimal space conditioning system.
Passive design models and balances a number of factors, including heat emissions from appliances and occupants, to keep the building at a comfortable, consistent temperature throughout the year. During cold months, Passive Houses use the sun, internal heat sources, and heat recovery rather than traditional “active” heating systems. In the summer, they use passive cooling techniques like strategic shading.
Before Passive House
Centuries before Passive House became a modern building model, buildings across the world were constructed according to many of the same principles. Icelandic turf houses, for example, date back to the 9th century. Wood was scarce in Iceland, so birch was used only for the structure, and then turf was laid to form thick walls and cover the roof. This functioned as an effective insulation, keeping the houses warm despite the frigid climate. Turf houses were also built in Norway, Scotland, Ireland, Greenland, and parts of Northern Europe (such as the Netherlands). In more temperate climates, like in southern China, some parts of Iran, and the coast of Portugal, buildings could be constructed without heating or active cooling systems, but rather ventilation systems that allowed for passive cooling.
But the events that led to the development of today’s Passive House model can be traced back just a few decades, to the 1970s. In 1973, the Arab members of the Organization of Petroleum Exporting Countries (OPEC) put an embargo on much of the West in response to its support of Israel in the Yom Kippur War. OPEC banned petroleum exports to the US, Canada, the Netherlands, the UK, and other countries, and cut oil production. As a result, in just two months the price of oil quadrupled. The embargo caused an oil shortage across the country, instilling widespread panic in citizens who feared they would no longer be able to fill their gas tanks, heat their homes, or run their factories. In her book, “Panic at the Pump: The Energy Crisis and the Transformation of American Politics in the 1970s,” Meg Jacobs writes: “Ever since, gas lines, cardigan sweaters, dark Christmas trees, and even wood stoves have become part of the collective memory of that era. At the time, Americans worried that life as they had come to know it – big cars, big suburban homes, and boundless consumption – was over.” Of course, this lifestyle hadn’t come to an end – the oil embargo only lasted six months, and consumerism bounced back with fury – but in the midst of the uncertainty, an interest in alternative energies was emerging. Engineers and architects across the country set out to design homes that would use little to no energy, to reduce dependence on oil altogether.
In Urbana, Illinois in 1976, a group of engineers and architects built the Lo-Cal (short for low-calorie) house using highly insulated envelope components, or superinsulation. The Lo-Cal house consumed 60 percent less energy than the most efficient buildings of the time. The following year, the Saskatchewan Resource Council used these same superinsulation principles to build the Saskatchewan Conservation House, and also introduced one of the first residential heat recovery air exchangers (HRV), a hot water recovery system, solar energy collectors, and a system to measure the building’s air-tightness. It further reduced the Lo-Cal house’s energy cutbacks.
By 1982, the term “passive house” was coined by American physicist William Shurcliff as the combination of superinsulation and passive solar strategies. The 1980s brought an explosion of tens of thousands of homes built in the US and Canada using these design specifications, but by the end of the decade, energy conservation was no longer a focus in North America. So Germany took these founding principles and started working to improve them. German physicist Wolfgang Feist further improved the passive house’s efficiency, developing a house with an annual heating demand of 15 kilowatt-hours per square meter. Feist went on to found the Passivhaus Institute (PHI) and create the definitive Passivhaus performance standard.
More recently, PHI and its principles have been reintroduced to the US – in 2007, Katrin Klingenberg and Mike Kernagis co-founded the Passive House Institute US (PHIUS). Interest in passive building has been rekindled and PHIUS has certified over 1,200 projects and 1.1 million square feet across the country. Each year the numbers grow, as more architects, engineers, and building industry professionals strive towards zero energy buildings.