Footloose and Carbon Free: The Passive House Standard

This article by Clarke Snell was originally published in the New Life Journal.

Okay, by now everyone has gotten the “human induced global climate change” memo, right? If not, here’s the executive summary: We burn a lot of fuel for heating, cooling, manufacturing, generating electricity, and driving stuff around. That burning releases carbon dioxide (CO2). As CO2 levels increase, the atmosphere basically traps more solar heat, causing temperatures to rise. The dynamics of all this are pretty complicated and the details are debated, but there is a frighteningly solid majority of climate scientists who agree that we need to drastically reduce emissions of CO2 (and other “greenhouse gases”) if we are to avoid catastrophic climate change.

In the US, our buildings are responsible for about 50% of our carbon footprint. Therefore, if we take this somber warning seriously, we need to do a major overhaul of how we build…and fast. Luckily, since carbon emissions come from energy use, the solution is simply to use less energy, something that saves money, reduces pollution, and makes us more self-reliant. That’s right, it’s patriotic, baby!

The concept is really pretty simple. First, we greatly improve the efficiency of the building itself. We do that by reducing heating and cooling demand by increasing insulation levels and carefully sealing up air leaks. We then install a nifty device called an energy recovery ventilator which allows us to bring in fresh air with only minimum energy loss. Next, we focus on the sun, letting it in the winter for heat and blocking it in the summer for cooling. We also add  interior thermal mass to help store this energy. Finally we choose the most efficient systems, including mechanicals, appliances, lights, and anything else that uses energy.

If we do all of this right, we can reduce heating and cooling loads by 90% over the norm and cut electrical consumption by at least 70%. At this point, we’ve significantly reduced the carbon emissions associated with our building. However, to reach carbon reduction benchmarks based on climate science predictions (translation: to save the world as we know it, yeah!!) we need to go even further. We have to make all of the energy our building needs without releasing carbon, which basically means without burning fossil fuels (coal and petroleum). No big deal. Solar, wind, and hydro electric power are all available options. What’s more, our energy demand is so low now, these systems can be much smaller and therefore more affordable.

To go all the way, we need to make enough surplus renewable, non-carbon emitting energy to offset the carbon emissions produced to build the building, even to make the solar panels and other renewable systems we have installed. If we do all of this, we have reached carbon neutrality. In other words, our building is not involved in carbon emissions and is therefore doing its part to avert “human induced climate change” (see memo…you did get the memo didn’t you?) What’s more, the building will cost almost nothing to run and will have wonderful indoor air quality.

What’s the catch? Well, though the concept is simple, the application isn’t. First of all, when we get to this level of energy efficiency, some of our typical building components are woefully inadequate. For example, conventional windows and doors are just sieves for heat and air loss. Though high performance fenestration is available, it’s very expensive. In addition, the tiny air leakage allowable to make this work is simply outside the experience of US builders. Very careful attention to a variety of construction details is required, often using tapes and gaskets that are hard to find for sale in this country. There are other difficulties, all of which have to do with money. Though these buildings cost considerably less in a lifecycle analysis, the fact is that it simply costs more money upfront to save money, energy, and carbon emissions in the long wrong.

Luckily, if we want to move in the direction of carbon neutral construction, and I feel we have to, there are sensible, proven methodologies already in existence. The one I like the best is a certification program called Passive House. There are many thousands of buildings that have been built to this standard and performance monitored throughout Europe, mostly in Germany, though almost none to date in the US. The Passive House standard is laughably simple to grasp. You are allowed a given amount of heating and cooling energy per square foot of building as well as a defined rate of allowable air leakage. You then have to design a building envelope (basically insulation and air leakage strategy) and mechanical system that will perform at that level regardless of the climate in which you live. In other words, you can’t take a common “out” popular in the US green building movement: build a low efficiency building then attach a huge, expensive solar electric system that provides 25% of a large household energy demand and call it efficient.

The Passive House standard is administered in the US by the Passive House Institute US. These wonderful folks are hard at work training consultants, certifying buildings, helping to import or develop requisite materials, and educating the public. For more information, visit their web site at  www.passivehouse.us . If you want to see the process up close, we are hoping to build a Passive House certified building in West Asheville starting later this spring. To find out more, go to our project website at www.thenauhaus.com.