Passive houses are called so because they draw all the required energy from ambient natural sources.
In the race to make the world a greener place, we seem to have identified quite a few carbon emission culprits. Vehicles, factories and even cement have been found to be some of the largest emitters of carbon dioxide. But what about entire houses? Not the wood-smoke spewing, rambling mansions of yore. It seems our modern, spiffy houses seem to be offenders as well.
This is where the concept of a “Passive House” comes in. A passive house is one that scores very high on energy efficiency as it relies on natural energy sources rather than an electric grid. Superbly self-reliant, a passive house is powered by the sun, the wind, the body heat of its residents and even the thermal energy that emanates from domestic chores such as cooking. To squeeze out every ounce of energy available from the atmosphere, passive houses are extremely well insulated, resembling an airtight container. If there is extra energy needed, then the renewable power units kick in. An efficient system of heat exchange ventilation technology enables the house to remain cool during summer and comfortably warm during winter.
Professors Bo Adamson of Sweden and Wolfgang Feist of Germany are the brains behind the passive house concept, which was developed in 1988. At the time, Sweden and Denmark were the hotbeds of the low-energy building movement, and the idea of a passive house was born out of this new green energy thinking. Two years later, the city of Darmstadt in Germany gained notoriety with the building of the first passive house. Standards and regulations to monitor passive house construction came into place by 1996 with the establishment of the Passive House Institute (PHI) also in Darmstadt.
The PHI estimates that energy consumption in passive houses is slashed by as much as a jaw-dropping 90% compared to average homes. While the common home uses an average of 160 kWh of heating energy per square meter of living space every year, houses built according to PHI standards use not more than 15 kWh per square meter. With such low usage of energy, energy bills no longer are a shock.
The key to making a passive house effective is the tight insulation, materials used and the construction technique. The U.S. Department of Energy estimates that cooling and heating costs can be reduced by as much as 30% when there is appropriate insulation in an average house. A passive house is made up of extra thick insulation layers and sports technically advanced windows that allow sunshine in but prevent the heat from getting lost. Roofs slant at an angle, preventing the inside of the house from being baked in the high summer sun yet allowing it to be warmed when the sun is lower during winter. When solar panels and other eco-friendly energy producing systems are added on to the passive house, it ends up using nearly zero energy. Such thoughtful construction “enables the structure to produce energy, use it intelligently, and retain it,” says Rolf Disch, an architect and environmentalist in Freiburg, Germany.
The cost of constructing a passive house might be much more than
that of a conventional structure but it is possible to retrofit existing
houses into passive structures and that is a cheaper and more
The passive house concept has gained traction in Europe with about 25,000 certified passive structures in existence so far, including schools, commercial buildings, apartments and homes. On the other hand, the U.S. has lagged behind in accepting the idea, with just around 13 passive structures in existence today. In fact, the first certified passive house in the U.S. was built as recently as 2004.
Once again, cost appears to be the factor. In Europe, the cost of building a passive house is around 5% more than a conventional home, while in the U.S., the PHIUS pegs the figure between 10% and 15%. According to Bronwyn Barry, Vice President Sales of California based Quantum Builders, the passive house movement would catch on if “financial incentives such as tax cuts or government subsidies” were provided, lures similar to those offered by the European Union.
The Passive House model is not the only green idea that is catching the eyes of builders and environment conscious consumers. A sort of sister concept named the “Active House” is gaining prominence in Denmark and elsewhere in the EU. Akin to the passive house, active houses end up conserving a huge chunk of energy. But the difference is that the active house provides homeowner controls to conserve energy. The world’s first active house, recently installed in Aarhus, Denmark, sports a computer controlled thermostat, which regulates the interior temperature by automatically opening and closing the windows according to the season, time of day and weather outside.
“Hopefully we’ll set a standard for what houses will look like in the future. We’re not building houses, we’re building an idea,” says Rikke Lildholdt, project manager for the Aarhus active house, to The Guardian. Whether it’s an active or a passive house, this green technology is aimed at changing the way we build our houses from the ground up.