Orchard Knoll recognizes that one of the most important aspects of building an energy-efficient home is the control of air movement across and through the sheathing system. Uncontrolled air changes through the wall assembly will reduce the effectiveness of exterior wall insulation, increase heating and air conditioning costs, decrease homeowner comfort, and lead to condensation in the wall cavities, attributing to conditions that cause mold and mildew. To minimize air leaks through exterior walls, Orchard Knoll had been using loose-laid house wrap with taped seams over oriented strand board (OSB) sheathing, then covered that system with an R5 rigid exterior insulation board. This combination system was effective in meeting their energy-efficiency goals and qualifying for builder rebates through a local energy provider, but was expensive, labor-intensive and redundant. They were looking for a solution that would provide equal or better air control, at lower overall construction costs.
In 2012, Orchard Knoll elected to replace the house wrap and exterior insulation board system with the Enviro-Dri® Weather-Resistant Barrier System, from Tremco Barrier Solutions, on a test home. The fluid-applied Enviro-Dri System is code-approved as both a moisture- and an air-barrier. One of the key benefits of Enviro-Dri that intrigued Orchard Knoll was that the system effectively and permanently sealed the home envelope from the outside, reducing air movement and rendering the two-step and expensive house wrap and exterior insulation process unnecessary.
On similar homes, the Enviro-Dri WRB significantly contributed a 50% reduction in air changes per hour (ACH) as compared to the control home, which used the standard house wrap and exterior insulation system. By reducing the ACH from 3.64 to 1.8, Orchard Knoll was able to generate a HERS® index of less than 60, which is at least 40% more energy-efficient than the reference home. Additionally, the lower HERS index qualified Orchard Knoll for higher energy rebates from the local utility company.
Today, every home built by Orchard Knoll is designed, marketed and sold with the Enviro-Dri Weather-Resistant Barrier System as the standard for air and moisture control…providing their buyers with the great home they want, at an extremely high value for the dollar.