They browsed the plans available on Coleman’s website, and while they found inspiration in several designs, none were quite right. “We thought we would adapt one of the existing plans to meet our needs, but our list of modifications ran quite long, so it made more sense to start from scratch,” Hennessy says.
Maximizing Passive Design With the exception of a loft, the 2,148-square-foot design remains true to Hennessy and Palmer’s original vision for a one-story house. In viewing plans online, the couple loved the second-floor towers and atriums featured in several of Coleman’s larger home designs, but the complexity of the roof and window schemes came with high construction costs that would have exceeded their $350,000 construction budget. Coleman came up with an affordable compromise—a 287-square-foot loft featuring a row of south-facing clerestory windows for daylighting and fresh air, and for providing summer passive cooling. “Even though the air-conditioning needed in this well-insulated home would probably cost less than $100 per year, Rita and Sean wanted the clerestory to keep the house cool without electricity,” Coleman says.
Dozens of emails over the course of one year gave way to the “RISE” design (a combination of the first two letters of the homeowners’ names), and the home’s ability to take advantage of rising air for passive cooling. A key feature is a series of seven operable clerestory windows at the peak of the south roof—which are opened and closed by remote control. At night, when outside temperatures drop below indoor temperatures, both the clerestory windows in the loft and the awning windows that sit low on the first-floor wall are opened to naturally cool the home. As the warm air in the home rises and is drawn through the clerestory windows, cooler air enters the lower windows, creating a thermosyphon of air movement. To capture the “coolth,” the windows are closed as early in the morning as possible, typically by 7 a.m. However, Hennessy says that “once the nighttime temps climb above 75°F, the passive cooling is no longer effective.”
Instead of a true south orientation, Coleman recommended that the house be oriented 10° east of south. In their West Virginia climate, having the façade favor a more easterly direction can help minimize afternoon heat gain during the summer and maximize early morning heat gain in the winter. Overhangs also help minimize heat gain in the summer, keeping the sun from shining directly into the windows throughout the afternoon. Oriented with its long dimension to capture the winter sun for free heating, the home features a 4-inch-thick concrete slab-on-grade floor, which is insulated with 3 inches of rigid-foam insulation (R-15). The thick concrete floors provide thermal mass to absorb solar gain in the winter and also help moderate temperatures during the summer. The foundation stem walls are also insulated with 3 inches of rigid foam.
The home uses doubled, 2-by-4 stick-frame walls on 16-inch centers with a 1/2-inch space between to form an 8-inch-thick wall. The air space between the stud walls creates a thermal break between the interior and exterior. With fiberglass batts between the studs to total R-30, and 1 inch of closed-cell spray foam to the exterior, the walls total about R-36, almost triple the code minimum (R-13 in their county) for wall insulation. “While spray foam isn’t all that green—it is petrochemical-based and has a high embodied energy—the amount we used is far less compared to the amount of foam used in structural insulated panels, which we had considered as a wall option,” Palmer says.
The roof is framed with manufactured wood trusses, which allow lots of insulation in the flat ceilings. In the bedroom wing, for example, 15 inches of blown-in fiberglass insulation were applied over 1-inch closed-cell spray foam (for R-60). A combination of fiberglass batts and spray foam were used for the vaulted, sloped ceilings throughout the rest of the house, for about R-66 total.