Zero Net Energy Homes Part 5 – Passive Houses

The Smith House - A passive house in Urbana, IL
The Smith House - A passive house in Urbana, IL

What if you didn’t have to heat your house at all, no matter the climate? Or at least, never turn on the furnace? Well, that’s practically what life is like in one of the “passive houses” designed with the principles of the PassivHaus Institut in Darmstadt, Germany. Recently featured in an article in The New York Times, No Furnaces but Heat Aplenty in ‘Passive Houses’

… these houses are part of a revolution in building design: There are no drafts, no cold tile floors, no snuggling under blankets until the furnace kicks in. There is, in fact, no furnace.

The idea of keeping all the heat inside a house and all the cold outside has been around for decades, but it took a number of technological innovations to do so while preventing stagnant air and mold. Passive houses are characterized by extreme levels of insulation (R-40 or more) and extremely air-tight construction to prevent drafts and heat leakage, coupled with sophisticated mechanicals – called air-to-air heat exchangers or heat recovery ventilators (HRVs) – that constantly refresh the inside air with outside air, while making sure the heat stays in.

Because they use 80% less energy for heating and cooling, passive houses are going to be a critical part of the goal of zero net energy homes. The less energy that’s needed to operate the house – and heating and cooling typically is 40% or more of the energy use in a house – the less energy has to be generated with solar panels or a wind turbine, lowering the cost of energy generation and improving the payback period.

And the cost of building a passive house, at least in Germany, is typically only a few percent higher than building a regular house of the same size, and the energy payback and the savings versus installling a traditional central system – not to mention the improved indoor air quality – makes the payback quite fast.

Over 6,000 passive houses have been built in Germany, but their take off has been slower here in the States. There are about a dozen “official” passive houses – sanctioned by the Passive House Institute US, the U.S. arm of the PassivHaus Institut –  in the U.S., although there are a number of unofficial ones as well, including quite a few mentioned on their forums.

The take off in the US has been slower for a variety of reasons – the different climates across the country, the fact that the expertise is primarily in Germany, and that much of the mechanicals – like the HRVs – need to be imported from Germany.

I bet you’ll be seeing passive houses going up on your street any day now, as the concepts are propagated into practice. The PassivHaus Institut website even features a section on renovating existing houses to passive house standards.

5 thoughts on “Zero Net Energy Homes Part 5 – Passive Houses”

  1. We built a passive solar house in the early 1970’s and had to create the things we needed to succeed. We did have to use a small Swedish wood stove in the lower level of the house, and an electronic air filter with a Heat pump for getting the permits necessary. The design of the house has been copied many times around town, but not the energy efficiency systems.
    It was so fun to be way ahead of the curve, it was fun to create and develop so many innovative ideas to use, and it was not fun to be so ridiculed for our efforts and endeavors and have no support.
    Very nice post. Now I will read the other 4 in your series.

  2. Patricia – thank you for the comment and the compliment. It sounds like you were leading the pack back in the ’70s! Now we just have to get everyone to build houses like you did more than 30 years ago.

    Nils

  3. We just need to find clients who will use our services because we just keep getting better and better, but folks just “chicken” out…If the peak of creativity for men is age 65…then hold on to your hats, because some really good stuff is bursting out in this green crisis and energy crisis and I truly hope it has some place to go…

    I am going to post about Zero Net Houses 2/3/09 on biking architect and mention your site. FYI…

    I just love reading about all this stuff and now I need to just stop researching and get writing! Thank you

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