In the late 1970s, Canadian engineer Harold Orr and his team embarked on a project to create a highly efficient dwelling in Saskatchewan. This initiative was a response to a local energy conservation directive during the oil crisis. Orr and his colleagues focused not on generating energy more sustainably, but on reducing its consumption. Their objective was to develop a superior insulating structure, rather than a more economical energy source.
The project led to the creation of a home featuring several key characteristics:
Advanced Windows with Strategic Placement and Shading: These windows minimize heat loss and gain, a significant factor in residential energy consumption, which can account for 25% to 30% of the total.
Airtight Construction: This design prevents air, and thus heat, from escaping or entering, thereby reducing the necessity for heating and cooling systems.
Insulation Suitable for the Climate: In some cases, houses are constructed entirely from insulating materials to reduce energy needs.
Design Free of Thermal Bridging: This approach involves removing weak points in the structure that can lead to heat loss.
Continuous Ventilation with Heat Recovery: The house employs a system that allows for the influx of fresh, filtered air through a heat recovery ventilation mechanism.
The culmination of these efforts was the 1978 Saskatchewan Conservation House, a trapezoidal, cedar-covered structure that achieved an 85% reduction in energy usage. This innovation laid the groundwork for the now internationally recognized passive-house standard in building design. This approach combines traditional building methods, like orientation for optimal sunlight, with advanced insulation and air circulation technologies. Developed further by German physicist Wolfgang Feist and Swedish engineer Bo Adamson in 1988, this standard also enhances health by offering superior air quality and noise reduction through its airtight design.
While passive houses currently represent a small fraction of multifamily construction, they exemplify a union of efficiency and applied physics, as noted by Bronwyn Barry, a leading figure in passive-house design and head of a Bay Area architectural firm. Passive design focuses on the building's exterior, demanding robust insulation and high-quality windows, often triple-glazed, to prevent heat loss. Addressing thermal bridges and ensuring airtight construction, as verified by blower door tests, are also essential. These homes are characterized by their simple yet elegant design, avoiding complex architectural features common in postwar suburban houses.
Although passive houses excel in energy efficiency, leading to up to a 90% decrease in heating and cooling requirements, they face challenges in air circulation compared to traditional buildings. This issue is mitigated by using heat or energy recovery ventilators, which allow for air exchange without heat loss.
Passive houses are not limited to cold climates; they are adaptable to various environments, requiring different window types and shading in warmer regions. The movement has grown beyond individual homes, with over 275 multifamily projects in the U.S., including educational institutions, affordable housing in New York City, and high-rise buildings like the Winthrop Center in Boston. Despite their growing popularity and competitive costs, especially with incentives introduced by the Biden administration's Inflation Reduction Act, passive houses still make up less than 1% of multifamily constructions in the U.S. over the past decade.