Climate change and our impact on the environment are likely to have a long-term impact on the planet. We look at passive housing, a concept that began in Germany with a pilot project in 1990 and is becoming more and more popular as a way of making a contribution to saving the environment.
What is a passive house?
A passive house is built to a rigorous standard designed to ensure the building’s carbon footprint is as small as possible. This includes super-insulation, heat recovery ventilation systems and controlled rates of air infiltration.
Passive houses can be certified as such through an exacting quality assurance process, to show that they meet the building standards set out by the Passivhaus Institut in Germany. To meet the requirements, the house must consume less than 15 kilowatt-hours (kWh) of electricity per square metre in a year, for all its heating and cooling. The total energy consumption for all household heat, hot water and electricity must not exceed 120 kWh per square meter annually.
What are the benefits?
Passive houses are so efficient that a conventional heating system is not needed, although in many places the building will still have a minimal heating system to boost temperatures. Passive housing generally uses around 90% less energy than most other housing to achieve a comfortable and steady temperate within the building.
The steady temperature means there is no requirement for active heating or cooling within the building, including boilers or air conditioning systems, which results in energy conservation and a reduction in the cost of home heating.
The air quality within a passive house is cleaner and healthier than standard construction and better sound insulation is achieved through more efficient (closed) windows.
How is a passive house achieved?
Passive houses are built to be airtight which prevents humidity from entering the building’s construction which can cause mould and sometimes even structural damage. A central ventilation system exchanges the used, moist and polluted air from within the building with fresh, filtered air from outside. The clean air is heated using the warm air as it leaves the building. This heat exchange system allows the building to have fresh exterior air while keeping the temperature steady and comfortable.
Solar energy is the primary source of heating, which means the size and position of the building, as well as its location, is crucial.
A layer of efficient insulation around the building’s envelope reduces heat transfer between indoor and outdoor spaces. Indeed, passive houses are so well insulated that there is no ‘thermal bridge’ as in conventional houses, where indoor heated air is allowed to escape outdoors through paths of least resistance, such as door cracks and open or inefficient windows.
The windows of a passive house will vary dependent on the climate but most commonly are tripled glazed with the gaps between panes filled with argon or krypton gas. A low-emission coating and insulated frames mean as much heat is retained as possible.
Apart from improved air quality and consistently comfortable temperatures, the construction is superior in quality compared to conventional builds and can result in minimal maintenance costs. The household also benefits from reduced noise pollution through improved insulation and smooth-running vents and fans.
Significant savings can be made on utility bills compared to conventionally built houses and there is even the possibility of rebates and tax credits, dependent on location. There is minimal reliance on energy providers and non-renewable energy sources and the investment can even increase the value of the home.