What is a Zero Energy Home?
This is an Energy Independent Cape currently under construction at the Kelsey Brook subdivision in Freeport, ME. It will be a zero energy home entirely producing its own electricity via solar panels on the roof. The house is totally framed and enclosed. Stay tuned as we progress..
Our Unique Wall Framing System
We designed the framing system you can see revealed in this first floor bedroom wall. Our goal is to maximize the R-factor, a measure of a building’s resistance to heat loss. The higher the R-factor,the more efficient the home will be to heat and cool. With this in mind, we frame walls with 2 x 8 studs, as opposed to traditional 2 x 6 construction. Next, we sheath the exterior with 2″ foam board attached to plywood. Finally, we apply 2″ x 3″ horizontal strapping to the inside of this wall. When the wall cavity is filled with dense packed cellulose insulation, our walls achieve an R-factor of 45, Compare this with the R-22 of traditional 2 x 6 frame with fiberglass insulation. At this stage of construction, this new home is well on its way to becoming energy independent.
Super Insulated Roof Framing System
Once the second floor deck is built, and the walls are framed we are ready to start framing the roof. We use 2 x 12 rafters which, along with 2 x 3 strapping on the slopes, provide the depth needed to insulate the exposed roof ceiling to R-58. The strapping acts as a thermal break. It prevents the framing timbers from being in contact with outside cold and inside warmth.
The R-58 in the sloped ceiling is achieved by using 3″ of spray foam along with 10″ of densely packed cellulose. Spray foam has the highest insulating value of any insulation. It is also the most expensive, yet is necessary achieve near R-60.
After 3″ of foam is sprayed between the rafters, 9″ of cellulose is blown into these cavities. The cellulose is held in place by Insulweb, a permeable fabric that allows moisture from condensation off the roof frame to dry toward the inside of the house. It is vital to the health of the house that this condensation be provided with a way to dry out.
Behind The Walls
The framed interior is the skeleton of the house. Studs outline rooms ready for the vital elements that, though hidden, will integrate to make this a comfortable home. At this stage of construction, the electrician and plumber work side by side. Wires thread through walls to outlets. Water lines position for sinks, toilets and showers. At the same time, a sprinkler system is installed, as required by Freeport building code.
The Heat Recovery Ventilation System (HRV), essential to a super-insulated air sealed house, now appears. Ducts remove stale air from the kitchen and bathroom areas, and provide fresh air to the bedrooms and common areas. The HRV is a critical element in building this zero energy home, providing a safe, healthy living environment.
Zero Energy Homes