In the middle of a small parking lot on the MIT campus stands a partially built, 800 square-foot house sitting on cinder blocks. It’s no ordinary house though. A group of about 40 volunteer students from MIT and other local schools are building it so that all of its energy needs are satisfied only by the sun.

The team by Kurt Keville, a researcher in MIT’s Institute for Soldier Nanotechnologies and Corey Fucetola, an MIT electrical engineering graduate student, with help from Tom Pittsley, a contractor specializing in “green” buildings—will compete with 19 other university teams from around in the world in the Solar Decathlon in October in Washington DC. The competition is sponsored mainly by the US Department of Energy.

The MIT house must be able to cope with Massachusetts’s climate and operate like any ordinary house; it must, for instance, generate enough electricity to heat water and power household appliances including a TV, refrigerator, washer, and dryer. The team will be judged in 10 contests (hence, the name ‘decathlon’), such as whether their house can supply 15 gallons of hot water in 10 minutes or less, whether the house can maintain a steady and comfortable temperature, and how much extra electricity it’s able to generate, based on how many miles the team can drive an electric car using that excess juice.

The students began designing the house in early 2006 and construction started last month. They have until late September to finish the house. They will then transport it in two or three pieces on trucks to the National Mall in Washington DC where they will have a mere eight days to put the pieces back together before the judges and the public arrive. (The team looked into transporting it by train—more environmentally friendly than trucks—but were told that the vibration from the train would be detrimental to the house.)

The team relies on sponsors to provide building materials for free or at low cost and to fund their way to Washington. Keville estimates that the retail value of the construction materials they’re using is about $350,000, but he and his team are building it for about $250,000.

I took a tour of the work-in-progress on Friday and got a rundown of some of the energy-saving technologies they’re using. The house will have plenty of windows and skylights and rooftop solar panels generating 9 kilowatts of electricity, but the house will collect and store the sun’s energy in other ways.

*Insulated walls*

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All walls and the ceiling will be made of two pieces of plywood with six inches of styrofoam sandwiched in between (photo above). Keville says these walls have about twice the insulating value as the walls in a typical (old) Massachusetts house.

*Radiant flooring*

Baseboard heating isn’t terribly efficient because heat emanating from the corners of the room doesn’t always get to where it needs to go (the center of the room) before escaping outside. So to better distribute heat throughout the house, the floor of the MIT house will give off heat. The floor will have a thin sheet of aluminum with small grooves in it (photo below).

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In the grooves will be metal tubes with hot water circulating through them. The MIT will put a bamboo sheet on top of this layer.

*Heat-generating wall*

A good portion of the south-facing living room wall (see photo below) will be made of 80 water-filled, translucent “bricks.”

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These blocks are designed to absorb, store and release the sun’s heat into the house.

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The outer layer of the block (right-hand side in the photo above) is filled with a porous gel that allows light in, but doesn’t let heat escape to the outside. As light streams in, the water inside the blocks heats up. At night, the water cools, releasing the heat into the house. The house’s many windows can be opened to let excess heat out.

*Sun-absorbing water pipes*

Some of the house’s water will be heated directly by the sun. Part of the external, south-facing wall will be covered with metal pipes (photo below shows only a mini, demonstration version) that will absorb the sun’s rays and use them to heat up the water flowing through them. Keville says that the house will still have an electric water heater, but these pipes should reduce the usage of that heater.

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