On the coast of South Carolina sits a beautiful little community of amazingly high performance homes. Called Bryant Park Cottages, it includes twelve homes varying in size from 700 to 1700 square feet, and living in small houses with small building envelopes is one of the best ways to save energy. Since the seventies, homes have become more efficient because of things like attention to air sealing, more and better insulation, and higher efficiency heating and cooling systems. Yet, the increased efficiency hasn't led to conservation because the efficiency dividend was spent on increasing size. We've dropped the kilowatt-hours per square foot and jacked up the square footage, resulting in no savings.
The reduced size is only one of the many features that makes these homes green, however. Each house is also insulated with spray foam insulation, and has minuscule infiltration. Because the building envelope is at the roofline rather than the flat ceiling, all of the ductwork for each house is inside the envelope, resulting in zero duct leakage to the outside. To balance pressures inside the house when bedroom doors get closed, the HVAC contractor installed jumper ducts. These ducts connect a bedroom with a hall, for example, so that when the air conditioner comes on while the bedroom door is closed, the excess air has an escape route to another part of the house instead of building up and increasing the likelihood of infiltration.
The homes also have mechanical ventilation, a requirement for homes as tight as these. They have front-loading washing machines that use half the water of a conventional washer and also wring the clothes out more so the dryer doesn't have to run as long. These appliances save energy and water. And speakiing of water, the homes have dual flush toilets and water saving fixtures as well. One of the homes also has a solar water heater.These homes are among the greenest in the Southeast and have been certified in the ENERGY STAR and EarthCraft House programs. The Home Energy Rating System Indices on these houses were in the 60s, meaning that they're more than 30% more efficient than similar houses built just to meet the energy code. They're not Zero Energy Homes, but they're still darn good!
The Bryant Park Cottages website has more information about the project.