On May 4, 2007, an EF5 tornado plowed through Greensburg, Kansas, leaving 95% of the city in ruins and most of the town’s residents homeless. Despite the tragedy, Greensburg’s residents remained in the area and decided that the city would be rebuilt with sustainability as a priority.
Prior to the tornado, Greensburg had been a declining town; its employment opportunities and population were shrinking. Today, Greensburg has become the site of one of the largest sustainability efforts in the U.S., offering new hope for residents and raising the bar for builders nationwide.
Many organizations have had a hand in determining Greensburg’s new direction. FEMA and the USDA were the first responders to the disaster. A nonprofit called Greensburg GreenTown, directed by Daniel Wallach, rallied residents and pushed for Greensburg to be rebuilt as an ecotown. The nonprofit involved residents in planning for their new city. “Sustainability became the linchpin of a vigorous renewal of the community.” says John Holton, an architect and engineer from IBACOS who has been providing support to builders in Greensburg. “Green design, of which a large cornerstone is energy efficiency, is a key focus.”
To help achieve greater energy efficiency in Greensburg’s new homes, the Department of Energy (DOE) assembled a residential team to provide training and field support to builders, developers, and other groups involved in rebuilding Greensburg. The team, managed by the National Renewable Energy Laboratory (NREL), includes IBACOS and Building Science Corporation. Building Science Corporation has provided workshops to discuss construction details, and IBACOS has operated the Greensburg field office, providing consulting in energy-efficient design and conducting HERS ratings to predict home energy use.
Ren Anderson, contract manager at NREL, used the BEopt computer program and set targets for homes to be 30-40% more energy-efficient than building code. His recommendation exceeds Energy Star requirements, which mandate that homes should be 15% more energy efficient than code.
A variety of construction is underway in Greensburg, including single and multi-family homes, stick framed, structural insulated panels (SIPS), insulated concrete forms (ICF), modular, and pre-built homes. However, a majority of the new homes are one story with a full basement, and most include a tornado safe room. Of the houses built so far, approximately 1/3 are built to 30-40% efficiency. However, some residents who rushed to have homes built early are now asking for energy-efficient updates.
Here’s a snapshot of the energy-efficient and durable features of some of Greensburg’s most exemplary homes:
Advanced framing techniques are used, including 2 x 6 framing at 24” o.c., single plates, two-stud corners, no jack studs, no cripple studs, no headers in non-load bearing walls.
Ductwork is sealed tight with mastic and located within the thermal enclosure, not in exterior walls or in the vented attic.
1.5” insulating sheathing with taped joints is installed in place of OSB and housewrap.
Rigid insulation is installed to the full height of the basement walls, which keeps warm, moist air from condensing on the cold walls.
A wider wall cavity allows for thicker R-20 insulation, and ceiling insulation is increased to R-40 to R-50.
Rim joists are sealed with spray foam.
Low-E, double glazed windows are installed with U-values of approximately 0.30 and SHGC of .35-.40.
Controlled fresh air ventilation is provided by either a heat recovery ventilator (HRV) or a damper-controlled duct to the return air plenum.
Flashing is installed at the head and sill of windows, at the base of brick walls, and at roof-to-wall intersections to avoid water intrusion in the walls.
High efficiency furnaces with an AFUE of 90 or higher are installed, and air conditioners with a SEER of 14 or greater are installed.
Several homes use ground source heat pumps with wells drilled to 150'-250'.
Greensburg’s emphasis on sustainability, green building, and renewable energy generation has attracted the attention of the media, product manufacturers, businesses, and builders. The Carrier Corporation and the Dow Chemical Company, among others, have donated products to be installed in some of the new homes. NREL is helping to develop a market for biofuels, solar, wind, and geothermal energy—all positioning Greensburg as a self-sustaining city with a hopeful future. To read more about the rebuilding of Greensburg, check out the DOE’s Building America website dedicated to information about Greensburg.
