Most renewable energy professionals are quick to point out that customers can get three times higher return by improving their building’s efficiency over installing a wind or solar system. And, of course, that makes total sense: why install a state of the art renewable energy system if it is simply going to blow energy out the top of the house or through leaky windows.
Germany, though, has taken energy efficient design to a level that is truly remarkable with their “passivhaus”. Check out a recent article in the New York Times about how these houses look, feel and work.
Passivhaus, involves super-insulating and sealing a home so tightly that it loses virtually no heat during cold weather, and, in fact, can be nominally heated by the sun, small appliances, and even human bodies.
This is not exactly a new idea–greatly enhanced building efficiency has been popular in America for almost thirty years–but the Germans have incorporated super-efficient air-to-air heat exchangers into a central ventilation system that makes it both healthier and more affordable for building occupants.
Check out this very interesting story about a cutting edge “passivhaus” project near Isabella, Minnesota, a place that regularly achieves winter temperatures in the -30 to -50 degree range Fahrenheit. Read what modern builders have to look at and consider in achieving both envelope sealing techniques as well as levels of insulation.
Of course details are important – be decisive is a well designed basic approach! An envelope can be airtight only if its consists of ONE undisturbed airtight layer enwrapping the whole volume. For each component of the envelope it must be specified, which part will form the airtight layer (e.g. the particle board or OSB in a roof construction). In a second step it has to be determined, how the airtight layers of the components will be connected to guarantee an enduring air tightness.
Insulation materials generally are NOT air tight. Therefore, the airtight envelope has to be designed and built separately. In timber constructions in most cases wooden composite boards are used (taped at the joints), in masonry construction a continuous inside plastering is sufficient. It is important, that the airtight envelope is continuous, without interruptions. This must be designed for, with particular attention to joints.
There is a lot of froth and roiling in the construction and design industry over how America is going to meet its energy needs in the coming century. Certainly, as new Department of Energy head Stephen Chu rightly believes, energy efficiency is priority number one for America’s built environment because it is the lowest hanging fruit. We agree.
And after a building or a community has their efficiency house in order, priority number two is to empower their structures with clean, safe and sustainable sources of renewable energy. That’s where we come in.