Sustainable Roofing Options
While some roofs are literally green, others use new technologies to collect and save energy in other ways.
In addition to offering the benefits of a traditional ridge vent, the Greenward system from Energy Alternatives harvests escaping hot attic air and uses it to preheat the incoming water of a hot-water tank. “This is not a solar system, although a majority of the heat comes from the sun,” explains Kevin B. Scott, president of Energy Alternatives. “It’s an ambient heat collector.”
Based on what you have seen and read about this project, how would you grade it? Use the stars below to indicate your assessment, five stars being the highest rating.
Introduced at last year’s GreenBuild show in Phoenix, the Greenward system utilizes flexible PEX tubing that contains a water/corn-based glycol solution that picks up the heat from escaping attic air. A differential temperature-control sensor, located by the ridge vent, is triggered when the temperature of the water in the storage tank is 20 degrees cooler than the temperature of the ridge vent. A circulator pump is then activated and pushes the hot solution down in a closed loop around the tank, where it heats up the incoming city or well water, before going back up to the roof area. “It’s a very low-tech solution for a high-tech problem,” says Scott. “A perfect example of utilizing existing energy that is normally wasted.” The system contributes to the Optimized Energy Performance credit in programs such as LEED for Homes and LEED for New Construction.
According to the manufacturer, the Greenward Ridge Vent can reduce energy consumption by just over 12 million BTUs a year and reduce CO2 emissions by just over 1,400 pounds annually. Scott says that many variables, including climate, shingle color, and attic size, affect how the system performs. The company is still collecting data from test homes in Tucson, the Carolinas, and Atlanta. One test, held in New York State on a day with temperatures of 85 degrees Fahrenheit, showed the ridge vent temperature at 120 degrees and the solution at 100 degrees, which helped the system raise 80 gallons of water from 65 to 90 degrees.
The system was recently installed in a LEED-certified home built by Habitat for Humanity Saint Louis, Missouri’s largest green builder. “The product installed like any other ridge vent,” says Kyle Hunsberger, director of construction for the chapter. ”After that, the rough-in is just a matter of connecting the PEX lines to the location of where your storage tank will be.” He cites an easy install, discreet profile, and the elimination of unsightly solar panels as the main benefits of the system. Hunsberger is monitoring the utility bills for the home and hopes to use the system on future projects.
Scott claims a main advantage of the system is the price point — the complete system comes in under $6000, fully installed. While he sees interest nationwide, “the hotter the attic, the more hot water we will generate.” For those in colder climates, the solution in the tubing is formulated in order to prevent freezing. The system works with both traditional on-demand water heaters as well as tankless hot-water heaters, adds Scott, and will help prolong the life of the heater.
In February, Greenward won a Green Dot Award, which rewards excellence in environmental responsibility. This year, the system will be on display at the Western States Roofing Expo in Las Vegas in June and the GreenBuild show in Chicago in November. Scott says that this is just the beginning of his company’s role in the green marketplace.
“This is our flagship product, and we have more products in the pipeline.” Energy Alternatives, Thiells, N.Y. www.nuenergyalternatives.com
[Reader Service: May 2010 #200]
share: more »
Get Architectural Record digital with free bonus content not found in the magazine!
Order back issuesócomplete your library!