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Our BatchGeo world MAP shows the locations of green building and renewable energy projects featured on Solaripedia.

Project

Enertia House (North Carolina, USA)

Credits: ©2009 Scott Nicholson/Watauga Democrat

Johnny Cooke of Sustainable Green Builders of the Blue Ridge is letting nature takes its course in providing energy for his new home. A builder in the area beginning in 1973, Cooke moved away to work in the Christmas tree industry before returning in 1997 to develop more properties. He began researching sustainable-building techniques and discovered Enertia, deciding to use the system for his own home. The Enertia design capitalizes on ambient heat and natural air circulation to spread heated air throughout a home or structure. The system also uses passive solar energy to help reduce energy costs. An air space of about 10 inches is left between the exterior walls and the interior walls.

 

Enertia House Builder

North Carolina developer Johnny Cooke built a new home using sustainable techniques that circulate sun-heated air to reduce energy costs. ©2009 Scott Nicholson/Watauga Democrat

“Anybody can buy the kit,” Cooke said. “You can custom design it yourself or have Enertia’s architects design it for you.”

The materials in the home in the Forest Glen subdivision near Howard’s Creek Road are inherently low-embodied energy, he said. “For instance, the exterior walls, the inner north wall and the inner south wall are all Southern yellow pine, which are farmed here in North Carolina and throughout the Southeast,” he said.

The resin in Southern yellow pine has a resin quality that holds heat or coolness for eight to 12 hours. “That is called ‘thermal lag,’” Cook said, to describe the way heat released over time.

Even in his unfinished house, Cooke has recorded temperature differences of 40 degrees between inside and outside temperatures. As the house has neared completion, the indoor temperature, with no additional heating sources, is averaging around 50 degrees. “We think it will go to somewhere between 65 and 75 (degrees) just with the Enertia,” Cooke said.

There are five 4’ x 9’ solar water panels which heat domestic hot water and water for radiant space heat that circulates through the concrete slab and the first floor. The solar hot water can be used to boost the house temperature if needed, and if there are several overcast days in succession, a wood stove will provide back-up heating.

The interior walls are Southern white pine made from trees that were cleared for the building site. More than 20,000 board feet of white pine was milled into tongue-in-groove planks by Eddie Moretz Lumber in Stony Fork. Locust and cherry on the property was used for decking, cabinets and vanities. There will be 3,400 square feet of heated, finished space in the house.

High Country Energy Solutions designed the house’s solar panels and photovoltaic systems, with 1.3 kilowatt-hours of expandable energy. Cooke said the system can be expanded to 2.6 kilowatt-hours, which would result in a net-zero energy use. Extra power will be sold to Blue Ridge Electric Membership Cooperative, Cooke said.

The roof has a special sheeting that insulates but also reduces heat in summer, with a larger air space in the attic. The same circulation system that heats the house in winter can be used to cool the house in summer, simply by opening two windows in the attic. Additionally, the sun is more directly overhead, minimizing sunlight in the house. The casement windows can be angled open to adjust the amount of cooling air circulation.

“It’s imperative that you are facing south or south-southeast to get maximum use of the Enertia technology, the photovoltaics and the solar water panels,” he said.

The basement, which also has South-facing windows, has an additional poured concrete wall to store heat.

The temperature throughout the house should be consistent in all areas due to the air circulation through natural convection, which can be augmented with fans.

“I am the distributor for this area and surrounding counties,” Cooke said, believing his home to be the first in the High Country using the Enertia design. He plans to build more of the homes for interested homeowners. For every tree cut for the Enertia system, four more are planted, leading to a reduction in carbon footprint in addition to energy savings.

Cooke said the timing is good for renewable energy and sustainable design. “We’re seeing an energy crisis not just in the United States but in the world, and I think that for any of us that choose to be more independent, it’s readily available, we just have to go get it,” he said.

Average cost of an Enertia home is between $140 and $160 per square foot. “A good rule of thumb with the Enertia homes is three to four times the package cost will be the cost of your home,” Cooke said. “There is a 35 percent federal tax credit and 30 percent state tax credit for installing photovoltaic and solar water. I will be getting a check from Blue Ridge Electric and North Carolina Green of maybe $30 per month, so there will be an immediate return on it. It should pay for itself in three-to-five years. We won’t be using electricity during the day, so we sell it during the day and buy it back from the grid at night.” Cooke said he’s had helpful alliances with Appalachian State University and Blue Ridge Electric, and he’s also exploring a “green certification” from the High Country Homebuilders Association. “In this economy, people are still going to have money to build homes, and I hope that even if they don’t build an Enertia home, they will use photovoltaic and green building if their property allows them to do so,” Cooke said.

To see additional examples of Enertia designs, visit:
Enertia Website
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