A Passive House works

New and improved
Energy is a big topic these days. It is expensive and costs are only going to go up. Plus, the more energy you use the more greenhouse gases are emitted, which contributes to climate change. Wouldn’t it be great to live in a house that uses much less energy, and saves you money each month?

There’s a new kid on the block in energy efficient home design strategies. The passive house. You may be thinking, passive solar houses were something from the 70′s. Didn’t that idea disappear along with bell bottoms? Well, bell bottoms came back, and so did the term passive but with a new meaning. “Passive house” is the English form of the German word Passivhaus.

First a little history
In the 70’s and 80’s passive solar design was new and seemed a hopeful solution. Put in lots of south-facing glass and plenty of mass (think concrete or brick) to soak up the heat and radiate it back inside the home at night. Problems cropped up though. These homes were too hot on sunny days and still required back up heating for cold days.

Then in the great snowy northeast super-insulated houses, with thick walls and special windows, were developed. But they were expensive to build and didn’t catch on. They did, however, later provide inspiration for Dr. Wolfgang Feist, a German professor who took a more exacting approach and coined the term “Passivhaus”.

What’s passive about a passive house?
Ideally it needs no heating or cooling equipment at all. It just sits there, passive, like a thermos bottle, keeping the heat in (or out on a hot day). To achieve this Dr. Feist developed a set of standards for energy use for heating and cooling per square foot; total energy use for all purposes; and airtightness.

It’s not easy being a passive house. Very careful design and construction is needed to be certified by Passive House Institute US. And it’s especially difficult to renovate an existing house to meet the standard. The basic components needed are thick and highly-insulated walls and roofs, very efficient windows (in some climates triple-glazed), and an incredibly airtight wrap around the entire house.

Wrap it up
When I first heard about the airtight aspect I thought, who wants to be sealed in like that? I’m starting to come around though. A lot of heated air is lost through small leaks all over a house and they add up. To be really energy efficient a tight envelope is a must. Fresh air is provided in two ways in a passive house. If it’s nice out, open a window. If it’s cold or hot out a small ventilation system is used that runs most of the time, quietly, bringing in more fresh air than conventional houses do.

I like how well thought out the standard is, and how ambitious too. If it ends up being more than you can achieve in your house, new or retrofitted, it still stands as a shining target to aim for.

At first the passive house model sounded like overkill. But as time goes on, and energy costs go up, I suspect it will start to sound more and more like the answer to our dreams.

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