This may not seem like the most interesting topic in the world, but it is one of the more economically accessible energy saving options for a new home builder. The Ellis Residence utilizes a hybrid insulation system. The wall and roof cavities are first filled with three inches of closed-cell spray foam insulation and then finished off with your standard batt insulation. This system allows the house to utilize the greater insulation and air sealing properties of the spray-foam in conjunction with the ease of installation and cost effectiveness of batt insulation. Often insulation is only looked at for its thermal properties (r-value), however, its ability to seal around outlets and joints in the exterior sheathing from the outside air temperatures is just as important. As the spray-foam expands it does just that. Spray-foam in the roof cavity also allows us to have an unvented roof assembly which if properly detailed and executed will reduce the possibility of condensation and consequent mold growth in the roof cavity.
On average the roofs in the Ellis Residence are insulated to an r-value of 60. In the state of Washington the building code calls for an r-value of 38.
