The Passive House Concept Passive house is a great example of the evolution of green building in the right direction. It is an extension of the super efficient homes that American designer/builders began in the 60's and 70's. At that time, some of the first homes were built that used around 80% less energy than conventional homes. In the 1990's, Bo Adamson and Wolfgang Feist took all this information and systematized it into the European PassivHaus system. The system has been reintroduced into the US and is on the rise fast.
Instead of prescribing what to do, the passive house system limits the amount of wattage that can be used for heating and cooling as well as plug loads and lighting. The passive house standard uses about 90% less energy for heating and cooling and about 70-80% less energy for electricity than a new American building.
This approach is much more logical then the approach of adding specific systems to achieve a "green" outcome like "LEED". By limiting the wattage, then all types of creative designs can be used to achieve the end. In addition the systems that actually work will be favored rather then those that are fashionable at the time. Solar is a great example of this. Solar is hot right now and many people are putting expensive solar arrays on homes without doing an energy efficiency retrofit. This approach in some cases can cost as much as 5xs as much as an energy efficiency retrofit yeilding the same energy footprint. If we were to take the Passive House approach. We could in some cases spend 1/5 the money to achieve the same overall energy footprint of a home and then use the remaining 4/5th of the money to produce excess renewable energy to power an electric car or sell back to the utility, build rainwater harvesting systems, plant food forests, and on and on.
The passive house system in its current form is geared towards new home construction, but currently we are working on expanding how the system can work in retrofits.
The basic components of a passive house system is this. Super insulating (r-30 to r-50) walls, roofs and floors, very tight air sealing, the elimination of thermal bridging in envelope, high perfomance doors and windows, proper solar orientation to take advantage of the solar heating in the winter and shading in the summer, the use of (HRV's) heat recovery ventilators for ventilation since the homes are so tight and neccesitate ventilation.
When it comes to retrofitting as well as new building, air sealing is the single most important area in building that can yield the most effective low cost energy conservation results. Most people have heard of R value and focus on that. But if you have a high R value and still have air leaks in the windows, doors, walls, floor or roof assembly the R value is destroyed. On the other hand if you take a home with relatively low R value and seal all the air leaks, the heating and cooling loads can drop dramatically. We don't realize that our homes leak a ton of air. But if they did not we would all suffocate when we left all our doors and windows closed for extended periods of time like sleep!
Another concept in green building that is relatively unknown these days is the concept of thermal bridging. We all know that metals conduct heat. But we rarely think about the metal components in our homes envelope that conduct heat. For example, aluminum frames of windows, metal handles on doors and windows, plumbing pipes, vent pipes, electrical wires and more. The edge of a concrete slab where it meets the wall assembly is another great example of a thermal bridge. If you think about it. There is absolutely no insulation at that point of the home. This is also a place where much air leaks into existing homes.
In the passive house system, we use thermal breaks in all those places. Basically insulating material in between any two conductive surfaces that protrude through the envelope of the house.
Most people these days are familiar with dual pane windows. The windows used in a passive house usually go much further than that. They not only have two, three or four panes but insulating material on all the framing as well as super air leak resistant latching and gaskets.
To be considered a passive house a home must use less than 15Kwh/square meter annually. That means that a 1500 square foot house would need to use less then 2100 Kwhs/year. The average American house uses about 10 times that amount of energy.
The beauty of the Passive house system is that it achieves its goals not with prescriptive lists like LEED or Build It Green, but with an end goal and performance tests. This allows the designers and builders to innovate in ways that can create breakthroughs beyond our current thinking.
The gains in energy efficiency that are created by adhering to the passive house system are an awesome benefit but the most profound benefits we will experience only after we come to know the myriad of innovations that will result from all the designers and builders working to meet these guidelines in their own new and creative ways.
Although the resources of our Earth are finite and deminishing faster and faster every day, the creative genius of the mind is infinite. When we align our society with the natural laws of human life on earth. Truly great things are possible.
There are three basic laws of human life on Earth. They are
- Earth's life supporting biosphere is finite and for the most part closed.
- The Sun is the main external input to the Earth's system. It and it's related sub systems are the primary power sources of Earth's life supporting biosphere.
- Humans have a creative intelligence to invent new things and solve problems. This intelligence is infinite.
When we live according to these basic truths that our biosphere is finite and powered by the sun and our creative intelligence is infinite, we can truly build the miraculous.
The Passive House System is another good step in the right direction towards humanities evolution into a life giving culture.
Thanks for your ear.
Mike