What is a Zero Energy Home?

Recently Completed in November 2014 – Kelsey Brooks 1st Zero Net Energy Home. Designed and Built by Island Carpentry of Georgetown, ME this highly energy efficient home has an array of photovoltaic (PV) solar panels designed to generate enough electricity to offset the estimated annual use. The house has 4 bedrooms and 3 bathrooms…

Recently Completed in November 2014 – Kelsey Brooks 1st Zero Net Energy Home. Designed and Built by Island Carpentry of Georgetown, ME this highly energy efficient home has an array of photovoltaic (PV) solar panels designed to generate enough electricity to offset the estimated annual use. The house has 4 bedrooms and 3 bathrooms…

 

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

(left) This exterior wall reveals our unique framing system. (right) Outside view of second floor wall.

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

The start of 2 x 12 roof framing at the gable end.

The start of 2 x 12 roof framing at the gable end.

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.

3″ spray foam between roof rafters.

3″ spray foam between roof rafters.

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

9″ Cellulose secured by Insulweb.

9″ Cellulose secured by Insulweb.

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.

Interior framing of the kitchen.

Interior framing of the kitchen.

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.

 

Island Carpentry 
Zero Energy Homes 
Georgetown, Maine 
www.island-carpentry.com 
207-371-2030