The Passive House, in German Passivhaus, is a building that requires very little heating. As such, it is perhaps one of the major architectural innovations of the last decade. This is especially true, if one considers that air pollution in the main Italian cities is largely produced by domestic heating, according to a study conducted by the environmental agency Ispra. If one includes the soaring energy bills that families are facing, then the idea of a highly energy efficient building becomes even more attractive.
Passive Houses are popular in Germany, Austria, Holland and Scandinavian countries. They have spread to the United States as well, and the sales are growing in China. It’s been a few years already, since they’ve started appearing in Italy as well. In countries like Austria, the Passive House will be the standard used for public buildings starting from 2015. The certifying institute that has largely contributed to this development has been the Passive House Institute of Darmstadt, Germany. The research center was founded by Prof. Dr. Wolfgang Feist who’s still in charge today.
Intrigued by what I had read, I had a conversation with Dr. Feist:
Dr. Feist, could you briefly introduce your institute?
The Passive House Institute is a center of independent research that is specialized in designing highly energy efficient buildings. Since its foundation, in the year 1996, it has developed building standards and improvements to the components that are commonly used in the construction of buildings. To help architects’ task of planning, the institute has devised a PHPP (Passive House Planning Package) and a 3d building interface, designPH. The research that we’ve been conducting focuses as well on applying the Stanard Passive House to different building types and climates zones. We’ve also been monitoring the buildings that our institute has certified.
How does a Passivhaus work? What are the main characteristics?
The Passive House Standard is a design concept that fosters environmental sustainability. It does so by minimizing energy use, as well as by providing a healthy living environment. The building is designed to offer an optimal indoor air quality and thermal comfort. This result is achieved by applying five basic building principles: 1) a strong thermal insulation of the building envelope; 2) improved windows and door fixtures (for cold climates triple glazed windows; 3) air-proof environments; 4) construction without thermal bridges; 5) a comfortable ventilation system with recovery of heat in cold climates and the control of humidity in wet areas. Applying these principles makes it possible to limit energy usage to 10 watts per square meter, both when heating and cooling the environments. In simple terms, energy consumption is reduced by 90%. The savings are what allow one to recover the initial investment.
How many buildings has your Institute designed? And where are they located?
The number of buildings that the Passive House Institute has certified nears 10.000 units. Most of them were built in Central Europe. One shouldn’t be surprised by that number, as the development started almost 20 years ago! Lately, we’ve been noticing a change in the geographical distribution. Research has proven that this building concept can be adapted to function in every climate zone. And so, one can find Passive Houses in China and Mexico, in New Zealand and Canada. You get the idea! The number of Passive Houses in the world can only be guessed. It’s probably higher than the number certified by our institute.
And what about countries such as Italy?
There are already many Passive Houses in Italy. Not only houses for individual families, but also offices, schools and public buildings. The majority of these buildings are located in the Northern regions of the country. There are some to be found in the South, for example in Sicily.
People say that Passive Houses are to costly to build, that they’re for rich people. Is this argument founded?
No, it’s a flawed argument. Monetary convenience is among one of the main advantages of this particular building standard. In many cities of Germany and Austria, municipal housing agencies have chosen the Passive House for their programs of social housing. There are higher costs to be anticipated, of course. The highly energy efficient structural components – such as window fixtures and the ventilation systems – can be expensive. The skilled labor that is required on the construction site is expensive as well. Compared to a normal house, the cost can be 6% to 7% higher. This is changing, however, as the number of experienced designers and builders is increasing. The real benefits of living in a Passive House can be be reaped in the long-term; as I’ve said, the building requires very little energy.
What are the savings in terms of energy consumption and green gas emissions?
It depends on the point of departure of the calculation, of course. In comparison to the existing building heritage that we have in Western Europe, houses built by applying the Passive House principles can enable savings of up to 90 %. The energy that is required to heat and cool a Passive House can be provided by renewable energy sources. In that case green gas emission would be reduced to zero.
Is is possible to renovate a building and transform it according to the Passive House principles? Or must one build from scratch?
It’s totally possible to transform and adapt existing buildings to be more energy efficient. In the majority of cases, however, it wouldn’t be the most efficient choice and we wouldn’t recommend it. Depending on the type of building, location, planning and some other technical aspects, we recommend a complete reconstruction that incorporates the elements of the Passive House. When renovation is possible, the objective of is to achieve the EnerPHit standard of efficiency through so-called retrofitting (editor’s note: retrofitting refers to adding new technologies or functions to an old system).
Do you think that we’ll witness a spreading of these types of buildings in the coming years, or do you think that people are not ready (culturally) to such a change?
All I can say is that the number of Passive Houses and retrofitted buildings has been increasing constantly, especially in Italy. I’m quite confident that the growth will increase. Fighting climate change and reducing energy consumption is becoming more and more important. Passive Houses are practical solutions that can be both economically and environmentally attractive.