Making It Right is a wonderful idea for rebuilding New Orleans Lower 9th Ward. The Pink Project's concept of building 150 eco friendly homes is a brilliant way to combine reconstruction with education about the planet's ecological and climate balance. The web site illustrates many specifics of the New Orleans design and appliance decisions. The designers made some very good choices for homes that have to be both affordable and sustainable. For today's market they are doing exactly the right thing.
On the other hand if money were no object my guidelines wouldn't change but my product and design choices would. My design principles include low energy use, low water use, low waste, local materials, and an effort to respect the site. The recent Solar Decathlon on the national mall featured dozens of entries that were all highly efficient and innovative. They proved that creating an energy efficient home is technically very realistic. I'm going to talk about five things I would do to make my building lovably sustainable.
I would design from the top down. The roof is out of sight to people inside, but it is capable of generating more than enough electricity and hot water to power the house and heating systems. Smart roof design would also add daylighting and ventilation to encourage summer cooling. My preferred shape is about a 3 in 12 pitch roof with a clerestory at the ridge. The illustration on the left shows a classic passive solar roof layout with clerestory. My design would cover the south facing roof with a combination of photovoltaics, active solar water heating, and a few small skylights. Today's PV systems can reliably produce one peak kilowatt for each 100 square feet of panel. On even a modest sized house designed like the illlustration there would be room for at least 600 square feet of well-positioned panels resulting in peak power generation of 6 kilowatts, more than enough for residential use.
It's very important to solar perfomance to design an overhang above the clerestory that lets in winter sunlight deep into the building but blocks the sun in the summer. These pictures show the Zion Visitor Center
Seasons dictate the building envelope. Hawaii, Florida, and Louisiana all have great solar resources and residential needs for hot water and electricity. However, they don't have much call for massive wall insulation and triple windows to keep our blizzards and Arctic winds. The roof design would work anywhere in the world, but the insulation beneath it and the walls that hold it up have to be matched to the climate. In my part of northern California, I would use at least R-40 in the roof and R-19 in the walls. In Minnesota I would bump those up at least 50%.
In addition to the insulation levels that define how stingy your building is about giving up heat, the building envelope can have varying degrees of thermal mass. That's a term that refers to materials that work like batteries for heat (or cold). Typical materials would be slab floors or concrete walls that are directly exposed to sunlight in the winter. They absorb heat while the sun is shining on them and give heat back during the night and evening. They are extremely useful for moderating temperature swings. People have been using thermal mass and passive solar energy intiuitively for thousands of years in places ranging from the Anasazi cliff dwellings to traditional adobe construction in the American southwest.
The key difference between early architecture and today's designs is that we have figured out that insulation should be added outside the masonry rather than inside. Many of today's rigid foams are sustainably produced and serve as excellent thermal components of our building envelope. My "spare no expense" house is going to have reinforced concrete faced with stone and thick concrete block/stucco in areas where I want a more traditional plaster appearance. These thick walls will be covered with 4 inches of polyisocyanurate foam which will be covered with stucco. The overall wall assemly will be between ten and 12 inches thick, earthquake and fire resistant, and immensely quiet and stable in temperature. Almost all the materials can be locally produced. If I was building in a more tropical area, I would opt for walls with less insulation, limited thermal mass, and much more ventialation designed into the building.
The floor closes the shell Once we have something to stand on we will have completed, in reverse, the construction process for a house. I like a softer floor than I can get with a slab and I like running plumbing, electrical, HVAC, etc. in the ample crawl space under the ground floor. I'm going with an R-19 insulated floor assembly built with Trus-joists and plywood or OSB. All of these materials make use of smaller and waste lumber that is more typical of our third and fourth generation forests. If you want a VOC or formaldehyde free house you could look for alternative plywoods that feature less outgassing.
Graphic of wood as a green resource from The Athena Institute
Windows and doors open the shell to the world. I'm a traditionalist with windows. I like standard casements, double hung windows, awning windows, and operable skylights. I am fond of the look and feel of wood windows and would probably go with whichever of Pella, Anderson, Marvin, etc. I could find most readily in my area. I have made my own windows before and it's way too much work.
So, to recap, the first five things I would design into my sustainable dream house if money were no object.
1. A great roof design with extensive photovoltaic system
2. Thermal mass of aesthetic delight throughout the building
3. High levels of insulation at roof, walls, and floor.
4. Raised wood floor with easy access for upgrading building utility systems.
5. Great operable windows, doors, and skylights.
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