Houses and other buildings are the product of centuries of evolution. As his numbers outgrew the cave, early man built simple box-like shelters from the elements with local materials. Over time he added features to these boxes to increase the comfort and suit his indoor activities. More than any systemic conception, traditional houses bear the marks of local needs, culture, and habits. The “basic box” of a house has essentially remained intact, but each new addition brought with it prescriptive minimum requirements, i.e., building codes.
During the post-World War II building boom, research sought to minimize construction costs, especially in war-ravaged Europe, without compromising safety and performance. Having documented Sweden’s factory-crafted housing on film in the 1980s, I was impressed by the efficiency and cost-savings of a Swedish system capable of producing sections of a complete, custom-designed, and highly energy efficient house in a single workday on a factory floor.
I filmed a custom-designed house being assembled onsite in a single workday by a crew of three. They finished the work and the home was ready to occupy a day later. That technology is a triumph of collaboration between private industry, government-supported science, and academic research.
During the 1970s energy crisis, researchers started looking at alternative sources of energy to substitute for missing and short energy supplies, often adding still more “widgets” to the old box — solar heat collectors and tanks full of water in which to capture and store the heat, for instance.
The “passivhaus,” or passive house, standard was born of a dialogue between Dr. Bo Adamson, of Sweden’s Lund University, and Dr. Wolfgang Feist, of the Institut für Wohnen und Umwelt (Institute for Housing and the Environment), in Germany. Instead of focusing on alternative energy sources, the two looked at the root of the building energy problem, searching for ways to minimize the use of energy in buildings. Why was there the need for so much heating energy? Where was the heat going?
A number of research projects followed, aided by financial assistance from the German state of Hessen. The first passive house was built in 1990 in Darmstadt, home of the international Passivhaus Institut founded by Dr. Feist.
The passive house flips traditional home building on its head. Instead of adding features to improve a basic box, it redesigns the box to meet a building energy efficiency standard that reduces a building’s ecological footprint by means of a computer-optimized architectural design process. The resulting ultra-low energy buildings require little energy for heating or cooling. Initially conceived for new buildings, passive design has since been adapted to energy upgrades of existing ones as well.
A passive house is designed and optimized drawing on a growing database of best practices, building materials and components, to meet a simple three-part performance standard.
A passive house consumes about one-fifteenth the energy of what an average similar-sized house consumes. It costs more to construct, but it requires no traditional heating system. Besides yielding ongoing energy savings, that alone can more than make up for the difference.
Looking toward a zero fossil-energy future, passive houses have become the gold standard for buildings. Thousands of examples worldwide prove that the concept works. And it is deceptively simple. Its planning software, with its extensive databases, optimizes the building’s performance, avoiding guesswork and costly mistakes in the field. A passive house has five essential features — super-insulation, avoiding thermal bridges, airtight construction, passive house-rated windows and doors, and heat-recovery ventilation, to both provide fresh air and control indoor moisture.
Because there are many more existing houses than new ones, a lot of research has been done — mainly in Europe — to adapt the passive house system to existing buildings. The principles are similar, but the details must match the “as is” needs of each individual building. The most promising approach is to “wrap” the building from the outside in a passive house-rated “cocoon.” The challenge, as always, is to moderate the cost. More on this in another column.
(Paul Kando is a co-founder of the Midcoast Green Collaborative, which promotes environmental protection and economic development via energy conservation. For more information, go to midcoastgreencollaborative.org.)