Insulating the Roof and Installing Mold-Resistant Drywall

Project: Building an Addition for an Elderly Parent, Episode 5, Part 2

The addition is nearly complete and it is time for the mechanicals, porch, flooring, and fireplaces. Homeowner Howard Brickman is putting a large farmer’s porch along the entire width of the home. He uses western red cedar for the decking and trim because of its natural tone, strength, and rot and insect resistance. A green building material, western red cedar boards are a dream to work with because they can be applied as decking or ceiling, vertical or horizontal siding, and with the rough or smooth side facing out.


Inside, Bob checks out the hydro-air boiler that runs the heat, hot water, radiant floor heat, and the indirect hot-water tank with a dual-coil feed to make use of the 30 solar heat collectors on the roof. Bob checks out the radiant-floor heating tubes, copper supply and return pipes, and the solderless sealed joints. The roof is insulated with dense-pack blown-in cellulose that is borate-treated for fire retardancy, mold and insect-resistance. Fiberglass-faced sheetrock completes the installation for mold-free walls. A new wood-burning fireplace is installed and faced with a lightweight thin-stone veneer. Prefinished red oak flooring is installed, the walls are professionally painted, and birch-veneer four-panel doors are hung.

Part 1: Constructing the Porch and Reviewing the Mechanical Systems
Part 2: Insulating the Roof and Installing Mold-Resistant Drywall
The roof of the new addition is being insulated to retain all the heat generated from the radiant heating system. Paul Johnson of Alpine Insulators reviews the installation process. Fire-retardant netting is stapled in place to hold dense-packed cellulose in place. Cellulose is a great thermal insulator and sound attenuator. In the interior partition wall where the bathroom will be located, cellulose will be installed directly against the drywall.

Bill Hulstrunk of National Fiber discusses cellulose insulation, which has been around since about 1920 and used extensively since 1970 in both new and existing construction. Borates are added to make the cellulose fire retardant, and mold and insect resistant. Because of the added borates, a propane torch can be put to the cellulose without igniting it. These borates are naturally occurring and the cellulose is made of 83 percent recycled content, making this type of insulation an environmentally conscious, green choice. The cellulose in this house is being used in an unvented application. Because the material is packed very tightly, it reduces the chance that warm, moist air will penetrate the cavity and create mold growth.

Georgia Pacific DensArmor drywall is being used throughout the addition. The face of this drywall is made of fiberglass so there is no danger of hosting any sort of mold growth. Attaching the drywall to a foam-and-concrete structure posed a bit of a challenge. To address this, steel J-beads were installed horizontally as nailers for the drywall screws.
Part 3: Putting in a New Fireplace, Painting the Interior, and Installing Doors and Floors
More and more homeowners are converting their houses into multi-generational homes for themselves, their children, and their aging parents. In Norwell, MA, Bob Vila meets a couple making room for a mother-in-law.