If you follow our blog, you know that we talk quite a bit about building science. In fact, we wrote a primer on how builders can use building science to produce more durable, comfortable, and energy-efficient homes. We also share information on effective air sealing and blower door testing -- a pain point for some builders having to meet new testing requirements of the 2012 and 2015 Residential IECC.
As any building scientist worth their salt will tell you, air tight homes start with great framing. Michael Schettine of AccuFrame Energy Seal isn’t a building scientist, but he has more than 45 years’ experience in home building, carpentry, and architectural reconstruction. His background has led him to believe that there’s a better way to reach air tightness targets, and it begins with a positive change in the way homes are framed.
Frame It Better
One recent estimate pegs the failure rate of blower door tests at 40 to 50 percent. Because buildings must be largely completed before initial tests, builders get one shot at achieving air tightness targets like 3 ACH50 in climate zones 5 and 6. If the building doesn’t pass, it can be costly and time-consuming to rework, reschedule and retest.
“I’m hearing that builders are using cases and cases of caulk for air sealing and trades still have to come back because they’re not passing the blower door test. That’s a problem,” says Schettine. He revealed that builders can spend as much as $300 per home for standard caulking products and still may have additional costs because of a failed blower door test. He argues the best way to a pain-proof system is to air seal during framing.
“Builders don’t know they’re often about $200 away from solving this problem of multiple testing, reworking, and rescheduling compliance audits,” he said. By incorporating a framing gasket into the exterior wall during framing, builders can drastically reduce air infiltration and build a better-sealed home. The home will pass a blower door test the first time and be durable enough for the homeowner to realize lower energy cost while increasing comfort.
“Sealing needs to be done during framing for the best performance,” he said. “Sealing gaskets in between the framing will not only result in a tighter, more durable home but will also avoid the number one problem you see with caulking and framing–shrinkage once it dries.”
How It Works
With the framing lumber ready, the gasket product (preprinted with framing stud locations marked on a liner) is applied to the top and bottom plates (see video). Then the wall section studs are installed and aligned according to the framing guide printed on the product. The liner is then peeled off, and the edges of the gasket are adhered to the edges of the plates. The double top plate is then nailed to the component, and the exterior sheathing is nailed to the assembly, completing the wall installation.
According to New York State Energy Research and Development Authority – which partnered on a project with Schettine, the framing gasket helps improve energy performance. By creating a four-way seal between the horizontal plates, face of the frame, and back side of the sheathing, the framing gasket reduces air flow through the assembly. When subjected to ASTM E283 testing, the product proved to reduce air intrusion through the assembly by more than 81 percent.
“With traditional framing and pressurization of the building due to heat/cooling cycles, air penetrates through any gap and connection point that’s not sealed,” he said. “Air sealing has to be continuous or else it’s ineffective. If you don’t have that continuous seal, air is pushed inward at the bottom-oriented strand board (OSB) and face-frame allowing air intrusion into the insulation cavity. During a wind event, this will cause energy loss and problems like ice damming where the loss occurs at the top plates and underside roof deck.”
Schettine provided test results from two identical houses in New York State as a comparison. One was built with AccuFrame Energy Seal. The other house was built using a comprehensive interior caulking method that resulted in a blower door of 3.81 ACH50. Both houses used fiberglass insulation and the OSB was taped. A weather resistant barrier was sealed on to the outside shell as well. The gasket-framed house, with no further interior air sealing or caulking, on the other hand, resulted in a 2.63 ACH 50 blower door test reading. Schettine’s final result was a more durable solution with a 30 percent reduction of air intrusion over caulking.
Changing Practices Through Training
Schettine believes framing gaskets are appealing to builders because the superior air sealing capability allows them to use cost-effective fiberglass insulation paired with the product to achieve a superior result. “Air sealing is the most critical component of the insulation job and is the key to an air tight home. Building Science Corporation conducted a study that shows all insulation performers equally well when properly air sealed. With this product, we’re stopping air from entering the OSB backside and the frame when other products are attempting to seal from the inside only. You have to stop air from entering the cavity and insulation to make a more air-tight assembly.”
But what would it take for this new approach to reach critical mass?
“All it takes to scale this approach is workforce knowledge and development. You must train framers in the new approach, but they’re willing to learn, and I’m starting to see traction from training schools. They’re teaching framers how to eliminate errors, increase productivity, and drive energy performance, and that’s where it all starts,” Schettine said.
The best part? It’s not cost prohibitive, according to Schettine and once the frame is complete, so is your air sealing detail.
“Building to the passive house standard beginning at $225 per square foot range is cost-prohibitive for most buyers, Schettine noted. “However, the gasket sealing approach allows mass builders of affordable homes to reduce cost and scheduling. The largest beneficiaries of switching to the gasket approach are the builders already using spraying foam, which is especially appealing to production builders dealing with tight budgets. And it delivers a return on investment for both builders and buyers by providing a more durable, long-lasting energy-efficient home.”