Passivhaus & Energy Efficiency

Dec 19, 2013

The Specht House in Thaxton, VA

According to Virginia Dominion Power the average monthly residential electric bill in the state is $119.82 a month. 

With the deep temperatures of winter and depending on our heat source we can find bills for a single month two to three times that amount.

But there's a method of home construction that for one homeowner has cut their electric bill by more than half the state average.

“Our typical energy bill is actually as low as $40 to as high as $62 to $65 so far. Our annual energy usage is so much lower than a standard home’s”  

That’s Jason Specht whose Bedford County Virginia home looks like any other--it is Craftsman style and about 1800 square feet-- but is so airtight they rarely need to use heating or cooling.

 “Every seam in the entire house before they wrapped it in styrofoam was taped up. They did what is called blower door testing to test the tightness of the house. If it didn’t fall within the standards of Passivhaus they would go back with a sniffer and smoke and pressurize the house and then they would pump smoke out and they could actually see where those holes were. They’d go back in and they would tape them over again. That’s providing that tightness.”

Jason mentioned meeting Passivhaus standards. That is a style of construction used in parts of Europe and in America, designers and builders like Adam Cohen in Roanoke are embracing it:

“Passivhaus is a German term. It’s a building that needs very little energy. It uses 90% less heating and cooling energy and 70% less overall energy. It’s basically a methodology using building physics and calculations to optimize a structure for low energy.”

Cohen says Passivhaus should not be confused with the solar fad of the 1970s also using the term passive. In this Passivhaus there three main tasks that go into creating an energy  efficient home with air tightness being number one:

“We make it airtight, just for reference, we lose 30-50% of our heating and cooling energy through infiltration and exfiltration; meaning through cracks and holes. So we make it airtight. We super insulate it and  we eliminate what’s called thermal bridges.”

Windows can similarly be thermal bridges where frames wrap unbroken from the outside in. Because of that, Cohen says the majority of windows made in the United States fall far short in energy efficiency:

“We in America look at the entire window so we can put in a very robust piece of glass and have a really poor frame so it will still be considered a high performance window. The Europeans break that apart and you have to have the high performance parts to make a high performance window.”

The windows used in this passivhaus are triple glazed tilt and turn with insulated frames:

“You have your tilt option…..which tilts in. And then you have your swing in options which allows for great cleaning of your windows, and it swings in just like a door would.”

Did you hear that sound? That’s the window closing and demonstrates the airtight seal they make. And that is key to passivhaus energy efficiency. Jason says the windows were the main contributor to increasing the home’s construction costs by about 5-percent. An amount he says will be returned in very low electric bills.

For more information, visit the Structures website.