How much more does it cost to build to the Gold standard of the NAHBGreen rating system than to Silver or Bronze certification? What specs would have to be upgraded to escalate a home’s rating?
Sure, you could calculate all of that on paper, but builder Roy Domangue of Wooden Creations, in Gonzales, La., northwest of New Orleans, wanted to find out in the real world of a jobsite—and help educate consumers, other builders, appraisers, lenders, and regulatory agencies about green building at the same time.
His project, Going Up, Going Green, encompasses a trio of new, 1,912-square-foot homes that are essentially identical except for variations in green building practices and products to achieve different levels of certification under the NAHB Green Building Standard rating system. The homes also meet the current IRC energy-efficiency requirements, comply with high-wind and flood-plain codes, and (except for the Bronze-level house) qualify under the federal Energy Star and Builder’s Challenge programs.
Initially, Domangue volunteered the rural parcels to build homes that would demonstrate pier-and-beam and raised-floor foundations—a common practice in flood-plain areas and now required by FEMA after hurricanes Katrina and Rita, but strangely missing from the 2009 International Residential Code (IRC). “We’re hoping to amend the IRC about proper pier and raised-floor construction,” says the builder, who is partnering with APA-The Engineered Wood Association and others to lobby for that amendment.
That was the “Going Up” part. The “Going Green” part was added soon after when Domangue agreed to chair the formation of a green building council for the local HBA. “I thought, let’s use the same three houses to show builders and others how to achieve green building standards,” he says.
That includes the cost to build and upgrade to higher ratings. “That’s what builders all want to know,” says Domangue, who kept diligent track of the materials and labor that went into each home. He found that upgrading to the Silver level (from Bronze) incurred a $5,455 premium (after a $2,000 state rebate), and that going to Gold cost another $11,035 above that, after applying $4,700 in state and federal incentives. “Cost efficiency and maintaining a price point are the biggest challenges to building green.”
The additional costs came from across a spectrum of upgrades. The air-conditioning systems, for instance, were scaled from a 14.5-SEER unit for the Bronze- and Silver-level homes to a geothermal, water-cooled heat pump for the Gold-level home that achieves a seasonal energy-efficiency ratio well over 20.
Domangue also improved the thermal shell. The Bronze baseline features 2x4 stud walls at 16 inches on-center with R-30 batt insulation, OSB sheathing, and housewrap, while the Silver version upgrades to a spray-applied, R-15 rockwool insulation, with foam panels over the OSB to create a thermal bridge. The Gold-level house is advanced-framed with 2x6 walls at 24 inches on-center and R-24 blown-in-blanket insulation. Windows went from a baseline U-factor of .35 to .29 to .24.
The builder will leave several sections of each home unfinished to expose green-building practices and products as teaching tools for a year’s worth of professional classes and open-house tours. “I took on the learning curve, and now I can help others learn about these techniques,” he says.
Even with a career-long commitment to energy efficiency and a pro-bono green home he built with Louisiana State University in 2000, Domangue gained a greater appreciation for sustainable building on this project. “Energy efficiency has driven my business for 28 years but I earned a doctorate on this one,” he says. “It created a whole new mindset,” that he hopes others will follow.
Learn more about markets featured in this article: New Orleans, LA.