Advanced Construction Techniques for Energy Efficient Building - Buildaroo Expert Energy Show
Terry Nordby and Peter Waring demonstrate advanced construction techniques for energy efficient building. Included in the videos are: proper installation of advanced framing, air sealing, insulation, sheathing, windows and exterior rigid foam insulation, rain shield and siding.
In advanced framing, wood studs are placed 24 inches apart instead of the conventional 16 inches. As a result, 15-20% less wood is used in the framing and more space is left for the placement of insulation in the wall cavities. The higher insulation content leads to a more energy efficient home. In a 2400 square feet home, you would save as much as $1000 in lumber and 5% in labor costs, and the home would also be 8% more insulating relative to traditional framing. Ideally, 2 x 6 wood studs should be used to maximize the amount of insulation that can be installed. With advanced framing, you can achieve an R value of 20, as opposed to R 14 with traditional framing.
Air sealing is often overlooked in floors and attic, although air leaks significantly reduce a property's insulative value. Terry Nordby demonstrates proper sealing of air leaks, which can be accomplished with either spray foam or caulking. Places to be sealed include: around pipes protruding through the wooden frame, the ceiling plate, wall cavities, any plumbing holes leading to crawl space and between the sill plate and foundation.
It is important to note that if there is an air leakage between the sill plate and the foundation, any chemicals used to treat plants or shrubbery near the home's ground level may potentially be blown and spread around the house. If you notice carpet stains on the inside of walls, this means that the carpet has been acting as a filter for air entering the house.
Terry uses blown cellulose insulation, made of newspaper mixed with boron to make it fire retardant, and densely packed into 3.5 pounds per cubic foot in order to avoid settling of the insulation. Terry uses blown cellulose insulation because it effectively fills in all wall cavities and surrounds piping or wiring. With traditional fiberglass insulation batts, it is hard for installers to cut the batts to fit exact, and this could lead to air gaps and air leaks. Another reason Terry prefers blown cellulose is because it is has an R value of 3.2 per inch which is very high, and it blocks sound.
Terry installs OSB sheathing onto the demonstration wall. OSB (Oriented Strand Board) is composed of recycled pieces of wood scrap amalgamated to form a board. For the sake of air sealing, Terry takes a precautionary measure of spray foaming the surfaces of the wall studs, and then installing the sheathing over the foam. In this way, the foam acts as an adhesive, in addition to sealing any air gaps. If the plywood or OSB wall is applied over the foam while it is wet, all gaps and air spaces are filled right away.
Installation of Windows & Exterior Rigid Foam Insulation
In the area around where the window is going to be installed, Terry applies furring strips onto the sheathing to bring out the wall to a more protruded level (so it is level with the insulation installed next). Rigid foam made of polyisocyanurate (PIR) is then installed offering a continuous insulation around the wall with no thermal breaks. This rigid foam has an insulation of R 6 per inch, the highest R value per inch of any insulation. An alternative to this is Foamular which has an R value of 5 per inch. The rigid foams should be taped together when they meet side by side.
Sealant is next applied between the furring strips and rigid foam insulation. The window is then put on top of the furring strips, and air and water sealing is applied around the edges of the window.
Rain Shield & Siding
Terry next installs Tyvek, a rain shield, on the exterior. This is installed to protect the house from moisture. When water goes through a homes siding, it hits this rain barrier and runs down to the ground. Furring strips are then put over the Tyvek in order to create an air space between the rain barrier and the siding that is put on last. This allows air to circulate behind the siding to allow it to dry if it gets wet, thus reducing the risk of deterioration. (Note: This practice of putting on furring strips on top of the rain shield is different from traditional building where this step is skipped. Instead, the siding is put right on top of the rain shield.) Next, the window trim is installed on top of the furring strips.
After installation of the rain shield, furring strips and window, a bug screen is applied on the top and bottom of the furring strips and Tyvek. Then the siding - in this case fiber cement Hardie board - is finally put on.