How passive building design achieves energy efficiency and how innovators are using the technique.
This summer, heat records were broken across the Pacific Northwest of the United States and buildings in the area, known for its cool, damp temperatures, were not ready. While the heatwave will subside, it has demonstrated that homes all around the world – even in places previously thought immune to heat waves – will need to be ready for prolonged periods of warmer temperatures. Architects around the world are working on solutions, and one of the design principles they are turning to is the idea of the Passive Building.
Passive building was first developed during the energy crisis of the 1970s when the OPEC oil embargo sent prices soaring and supercharged the interest in designing buildings that were extremely energy efficient. In 1976, a group of engineers and architects from the University of Illinois Small Homes Council designed the Lo-Cal house, which used the principle of a highly insulated envelope, to reduce energy consumption by 60 per cent. By the late 1980s, a fully-fledged passive house movement had launched in North America. But as oil prices lowered, the United States shifted its focus away from energy conservation, and advances in passive building design shifted to Germany and the Passivhaus Institute (PHI).
Today, the PHI defines a passive building as one designed and built in accordance with these five building-science principles:
The use of continuous insulation throughout the entire envelope without any thermal bridging.
Use of a nearly airtight building envelope, preventing infiltration of outside air and loss of conditioned air.
High-performance windows (double or triple-paned) and doors, along with management of solar gain (for example, through orientation of the building) to exploit the sun’s energy for heating purposes in cooler seasons and to minimise overheating during the warmer seasons.
Use of some form of balanced heat- and moisture-recovery ventilation.
Use of a minimal space conditioning system.
Passive building achieves energy efficiency primarily through separating the exterior environment and interior of a building with an airtight envelope. This includes incorporating high-performance windows, extra insulation in the walls and roof, and spatial orientation to maintain consistent and comfortable indoor temperatures throughout the year. Passive buildings also use ventilation systems with heat and moisture recovery for increased air quality and efficiency. Passive homes use up to 85 per cent less energy for heating and cooling than the average home.
Many innovations in passive house design are coming from areas where extreme heat is a regular occurrence. In Phoenix, Arizona, architecture firm Studio Ma specialises in incorporating elements such as shading, window orientation, overhangs, and cantilevers to shield buildings from the heat of the desert. They have also determined that using lighter, better insulating materials on the outside of buildings and limiting the heat that falls on them can limit the variation in internal temperatures.
But passive design does not need to be based on the latest technology. Elements of passive design have been used for thousands of years, from the adobe homes of the North American southwest to the underground houses in Morocco and Tunisia. Many of these traditional elements are being incorporated into today’s passive buildings. In Gurugram, India, architects have designed a girls’ hostel that uses traditional latticed brickwork to reduce the amount of heat absorbed into the interior.
Densely planted courtyards and double-height ceilings combine combined with the double-skin façade to eliminate up to 70 per cent of the heat which is normally absorbed. An atrium acts as a solar chimney, allowing light in while drawing heat out and away from the building.
Buildings do not have to be large to take advantage of passive design. New Zealand architecture firm Condon Scott Architects have designed a tiny home that incorporates passive principles, such as floor-to-ceiling, a glazed window on the home’s north side, deep eaves and structural insulated panels. The house maintains a consistent temperature using virtually no additional energy.
While there are still few fully passive buildings, an increasing number are incorporating elements of passive design which save energy, add comfort and just make good design sense. For example, the Shenzhen Energy Mansion skyscraper reduces heat build-up from the sun with a warping, striated façade, panels of double-insulated coated glass to soften the light and structural folds to offer scenic views without generating heat from direct sunlight.
In Spain, Madrid-based Husos Arquitectos has created an apartment layout that maximises ventilation to eliminate the need for air conditioning. The design included the use of “breathable mortars”, lightweight materials and a vertical edible garden that passively cools the living space and prevents overheating in the summer.
It’s clear that warming global temperatures, combined with the need to reduce carbon emissions, are going to mean passive building design incorporated into mainstream architecture. In the future, all buildings will need to include not just existing passive design standards, but likely a range of design solutions for coping with hotter weather using less energy.
Written By: Lisa Magloff
6th August 2021