Holliston LEED House

This is the story of a family who built the first LEED "green" house in Holliston, Massachusetts. We were trying to spend no more than it would take to build an ordinary house,and maybe even succeeded. The dust is still settling.

Thursday, April 16, 2009

Water to heat

This is our new Envision, a geothermal water source heat pump by Water Furnace. Our dual capacity unit is DV064A111INTL. This is an air ducted system which will deliver both heat in the winter and cool air in the summer. This furnace, rated 26.1 EER and 4.7 COP at our level, is so far above any energy and LEED requirements that they'll probably raise the levels. In essence, at an entering water temperature from the ground of 50° (ours should run closer to 55°), the Envision extracts the heat from the water and returns it to the ground. The air, then heated at 50, is boosted by heat coils within the furnace to your desired temperature. The beauty of our open loop system is that it takes water out of the ground, changes it 10 degrees, and returns it to the ground exactly the same as it came in. The water touches nothing that can pollute it.

During the heating cycle, the system uses the loop to extract heat from the well water. As the system pulls heat from the loop it distributes it through a conventional duct system as warm air. In the cooling mode, the system air conditions your home by reversing the heating process. Instead of extracting heat from the ground, it is extracted from your home and either moved back into the earth loop, or used to preheat the water in your hot water tank. And once the heat is removed from the air, it is distributed through the duct system in your home.

The physics are fairly tricky, but the fact of the matter is that it is similar to an air-source heat pump only (especially in the Northeast) hugely more efficient using 50-55 degrees as a starting point rather than the much colder air.

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At April 16, 2009 at 5:47 PM , Blogger Wolfen said...

And it is so stylish!


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