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Ambient water heater premieres at Greenbuild

November 13, 2009 |  8:44 am

Grv_system_web_large About 90% of the hot water that pours from Californians' bathroom and kitchen taps is warmed with natural gas, but all those hot showers and hand washings come with a cost. Burning natural gas pumps out hundreds of thousands of tons of greenhouse gas emissions each year -- and that's in California alone.

Tankless and solar water heaters are good options for reducing hot water's carbon footprint. Now a different system is premiering at the Greenbuild sustainable design expo, ending today in Phoenix. It's an ambient system that uses the heat naturally trapped in a home's attic to heat the water in an existing water tank. It's called the Greenward Ridge Vent System, or GRVS.

Developed by a construction contractor who thought there had to be a way to harness attic heat, the GRVS works by taking the trapped heat in the uppermost part of a house and channeling it through the roof's ridge vent, which is plumbed with tubing filled with a glycol-and-water mixture. The hot air warms the liquid in the tubes. That liquid then flows to a 70-gallon storage tank that heats the water coming into the house from the water utility. The system then transfers the heated water from the storage tank to the existing water heater, where it's available for use. The glycol-water mixture then returns to the roof to reheat.

'It's not a solar collector. It's an ambient heat collector," said Kevin Scott, president of Energy Alternatives, the Connecticut firm that makes the system. "At night, after you've used all your water, bathed your kids, done your dishes, your attic is still very hot. It could be 110 or 120 degrees, so your water is being heated while you're sleeping, so when you wake up you'll have preheated water."

According to Scott, an average family of four uses between 70 and 90 gallons of hot water each day; 60% of a household's monthly energy usage is to heat water.

The system can be designed into new construction or installed into an existing home. A new roof or new water heater is not required. Installation could be done by different contractors, Scott said. The ridge vent is best installed by a roofer, and the storage tank is the domain of a plumber. An HVAC specialist, Scott said, could do both.

The suggested retail price for the system is $3,599. With installation, the total cost would be about $5,000, Scott said. Information: www.nuenergyalternatives.com or (888) 565-8418.

-- Susan Carpenter in Phoenix

Illustration credit: Energy Alternatives