Monday, April 7, 2008

What is an EarthCraft House?

As I wrote earlier, one part of our purchasing process was to hire a builder friend of ours to look over the house design and give us advice. This was useful not only in helping us make a few design modifications, but also to help us understand exactly what we were purchasing. Our friend wanted to know exactly what was meant by an EarthCraft home and specification, and how that matched up with building standards he was familiar with in Montgomery County, Md.

The first place to start is with Church Hill Homes "Green Building Fact Sheet". Although this does not tie directly into an EarthCraft checklist, this is great for seeing how Church Hill Homes is actually building the house. For instance, it talks about the "Zip System Wall and Roof Sheathing". You can see this on the photos as the green panels on the outside with black tape lines between. This for the most part eliminates or at least reduces the need for Tyvek house wrap. It looks like something that saves time when building the house and also can make for a more tight envelope. While the Earthcraft specification may not say this Zip System is needed, using it is one way to make sure the house will conform to EarthCraft standards.

So I advise potential buyers to look over the Green Building Fact Sheet as a way to see how Church Hill Homes will actually build the houses. It is where "the rubber meets the road" so to speak. It does not say much about the actual EarthCraft homes specification however; for that we must look elsewhere.

I see EarthCraft Virginia has recently put up a website: EarthCraft House Virginia. It is a little "green" yet (couldn't resist) but it has a resources page with very useful documents. The one our builder was most interested in (and the one I found fun, although potentially overwhelming to read) is the EarthCraft Virginia Technical Guidelines (1.5 MB). Here is everything you might want to know about the big and little things that set an EarthCraft home apart from normal houses. What I found most interesting is that EarthCraft encompasses the entire design and building process: there are sections on how to clear the land and develop the site all the way to very detailed descriptions and drawings of how to seal around vents and pipes coming into the house.

From what I understand, an EarthCraft specification is fairly flexible - there are specifications for all aspects of the building process, and points are awarded in each category (site plan, clearing, erosion control, insulation, sealing, HVAC systems, and so on) for meeting each specification. A builder has some flexibility in choosing between these guidelines in order to achieve an overall score that makes the finished product an EarthCraft house. I am looking forward to seeing the completed worksheet for our house.

The Virginia EarthCraft House site has other files available on their Resources page on sealing, indoor air quality, etc. There are also worksheets and checklists so you can see the way a builder can combine choices to achieve EarthCraft certification.

Other useful resources I have found are:
  • "Living in the Green", an article about renovation and new construction meeting EarthCraft specifications in Atlanta.
A huge difference between our home and traditional construction is the way the house envelope is treated. Traditional construction has the envelope extending from the first floor to the ceiling of the top floor. Indoor air needs to migrate to the attic, where a venting system removes heat and humidity from this air. In this design two things are critical: being able to insulate the house from the attic space while not unduly restricting the ability for air and especially humidity to pass through to the attic. Then the attic and roof absolutely has to be able to vent this air to the exterior, otherwise mold and mildew will accumulate in that space. There can also be mildew problems in the crawlspace if enough airflow is not built into the design, or even with it as moist outside air contacts the cool underside of the house, or cool air conditioning vents and condenses.

Our house will behave quite differently: the attic and crawl space are part of the house envelope and the heating and cooling is extended into those areas so they do not need exterior venting. They stay about the same temperature as the rest of the house so heat and humidity differentials are greatly reduced, in short, the house is more comfortable.

This building method was greeted with skepticism by builders unwilling to change what have been fairly static construction methods for a hundred years or more. Even now after years of successful houses built using this method I encountered worries ranging from interior air quality and humidity control to the roof shingles melting due to increased heat in the attic.

After all my research I still found myself with many questions, some of which were inspired by the criticisms I noted above about humidity and shingles. Josh Goldschmidt of Church Hill Homes has answered these questions to the best of his ability and I am satisfied that I will be living in a more comfortable as well as more efficient house. And to his credit, Josh was not afraid to say that he didn't know 100% why these things worked so well, but that he has simply experienced the result. Furthermore I have found him truly excited about the whole process; he freely admits he is looking forward to living in Belvedere because it will enable him to do his job better as he will have direct knowledge of what is like to build and live in his own EarthCraft house.

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