June 2005
The NextGen H2 house utilizes solar energy in several ways, including a photovoltaic system, a solar hot water and space heating combo system, properly sized overhangs, and orientation specific glazing.
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The project known as NextGen recently received an award in the affordable housing category from the Colorado West chapter of the American Institute of Architects, demonstrating that cost-effective housing can also be environmentally friendly.
The NextGen project is designed to reduce energy use and increase cost efficiency in new houses. NextGen partners include the Building America Program, the Massachusetts-based Building Science Corporation, Community Office for Resource Efficiency, Fenton Construction, Green Line Architects (formerly Novy Architects), and many other specialists and advocates of sustainable construction. NREL performed a field evaluation of this project in December 2004.
NextGen has developed two different models of three-bedroom, two-bath houses. The homes are affordable, durable, and replicable.
The first model home (H1) is about 19% more efficient than the Building America Benchmark based on whole-house energy use. It incorporates extra insulation and passive solar heating.
The other sample home, known as the high performance home or H2, produces up to 75% of its hot water using a solar heating system and produces 50% of its own electricity from photovoltaic panels, which collect solar energy and turn it into electricity. The house uses about 52% less energy than the Building America Benchmark, exceeding the design goal of 45% by a substantial amount.
Both homes are constructed using 25% to 35% less materials than other houses. Studs are a regular two feet apart throughout the homes, and the exterior walls are sheathed in foam-instead of plywood-meaning less wood is needed. Measurements are based on these two-foot increments, so boards can be ordered to length and there is less waste. The windows are high efficiency units, reducing heat loss while still allowing solar heat gain in the winter. Overhangs shade the south-facing windows from the summer sun.
Instead of the typical fiberglass batt insulation, spray cellulose insulation is used, reducing the number of voids in the insulation created by wiring and piping obstructions and non-standard wall cavity shapes and configurations. Attention to air sealing details helped to get the infiltration of the homes well below normal levels. These and other envelope improvements led to a 25% reduction in heating energy consumption.
In Colorado's Garfield County, NextGen homes were sold for $215,000 to $225,000 to families who qualified for affordable housing.
The homes will be monitored by the Building Science Corporation and the National Renewable Energy Laboratory.
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