The Solar Harvest home in Boulder was a highlight of the 2005 Tour of Solar Homes last October.

Credit: Ecofutures Building, Inc.

General Housing Category
Boulder, Colorado

Ecofutures Building, Inc. in Boulder built the city's first net-zero energy home in December 2005. This home is called Solar Harvest and produces as much energy as it consumes over the course of a year, all of it from solar energy. It has no backup heating source from fossil fuels and no air conditioning.

	Renewable Energy Features
	Project Team

The Solar Harvest home is Energy Star® rated and scores 97.7 on a home energy rating (HERS) scale of 100. The HERS rater, Paul Kriescher of Lightly Treading, Inc. in Denver, said this home scored the highest HERS rating of all of the 30,000 homes tested in Colorado. Ecofutures offers public tours and publishes online details about the home. http://www.ecofuturesbuilding.com/taxonomy_menu/1/13/21

Solar Harvest is no rough cottage. There are five bedrooms and two guest suites. Altogether, there is 4,585 square feet (sf) of conditioned living space. And there is a 400 sf unfinished garage and a 600 sf unfinished carport.

The Solar Harvest home uses a sunspace next to the south wall to collect solar energy for heating in the winter. Fan-drive ducts carry the warm air to the rest of the house.

Credit: Ecofutures Building, Inc.

Renewable Energy Features

The Solar Harvest home contains the following renewable energy features:

• Solar photovoltaic (PV) system rated at 6.8 kilowatts (kW).
  The PV array is mounted in two arrays on separate portions of the roof. Both arrays are flush mounted on the roof (see photo); one lies at 20 degrees tilt and the other at 40 degrees. The system is larger than the needs of the house, and so it is a net producer of electricity. The local utility, Xcel Energy, purchases the excess generation through a net metering arrangement.
• Passive solar design.
  The Solar Harvest home has 275 sf of south-facing glass that heats a sunroom. Fans and ducts carry warm air to interior spaces.
• Solar thermal heating.
  The home has twelve evacuated tube hot water collectors mounted on the roof that heat a hot tub, domestic hot water, and living spaces. The collectors are connected to a 6,000 gallon cistern located in the basement, which provides thermal ballast for the home. The hot tub is kept at 103 degrees Fahrenheit. A pump circulates hot water through pipes mounted in the floors for radiant heating in the winter.
• Natural cooling.
  The home has an operable skylight located in a high bay that allows hot air to escape in the summertime. Warm, exhaust air also leaves the house through attic vents. Finally, a whole-house fan pulls 1600 cubic feet per minute of exhaust air out of the during the summer nights, which pulls in cool, fresh air in from outside.
• Geothermal pre-heating and pre-cooling.
  Outside air is brought into the house through an energy recovery ventilator that exchanges energy with the exhaust air. The fresh air intake passes through 140 feet of 6-inch plastic (PVC) pipe buried eight feet deep and surrounding the house. The system, called the Ultimate RecoupAreator is built by Stirling Technologies in Athens, Ohio. It provides fresh air directly to bedrooms and to the exhaust fans in the kitchen and bathrooms.

CRES 2006 Vice President Doug Seiter awards a member of the project team the 2006 Colorado Renewable Energy in Buildings Award.

Project Team

The following organizations share the 2006 Colorado Renewable Energy in Buildings Award in the general housing category:

• Ecofutures Building, Inc., in Boulder; general contractor
• Eric Doub and Catherine Childs in Boulder; designers and owners
• Pete Chandler, Living Space in Boulder; healthy home consulting
• John Arndt, Gebau Engineering in Boulder; engineer
• Ken May, Industrial Solar Technology in Golden; engineer
• Peter D'Antonio, PCD Engineering Services, Inc. in Longmont, engineer
• Michael Haughey, Silvertip Integrated Engineering Consultants in Westminster; engineer
• Gary Rossen, Western Soils, Inc., in Lyons; engineer.