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Anatomy of a first class energy upgrade

Paul Kando

If you have money stuck in some CD or investments that barely keep up with inflation, consider investing in upgrading the energy efficiency of your home for a far better return. A case in point is this 1965 vintage 2,119 sq. ft. cape in Northport. At the time of a fall 2011 energy audit the cedar shingled house was surrounded by bushes, planted by an earlier generation, virtually touching the building, and the family burned 1100 - 1200 gallons of oil annually for heating and hot water, maintaining an average indoor temperature of only 58-62°F. Calculated energy use was 6.56 kWh per Heating Degree Day, with a carbon footprint 16.7 tons of CO2, about 15.7 lbs per ft2 of heated floor space.

Upgraded House
photo credit: Paul Kando

The home's 2x4 framed, fiberglass insulated walls had a total thickness of 5.5" and a total R-value of 14, the 2x6 framed, 7.5" thick, asphalt shingled roof had an R-value of 21, and the 8" thick poured concrete basement floor and walls an R-value of 1.6. The blower door measured 5.05 air changes per hour at 50 Pascals pressure (ACH50), which corresponds to a complete natural air change every 2.5 hours. The combined area of all the air-leakage holes and gaps throughout the heated envelope came to 0.9 sq. ft. open to the elements 24/7. Heat losses totaled 35,008 kWh/yr, of which 36.9% were lost through the walls, 21.9% through the basement, 18.5% through windows & doors, 16.0% through air leakage, and 5.4% through the roof. The remaining losses were due to miscellaneous causes, such as uninsulated pipes in the basement.

The energy audit report listed a number of "low hanging fruit" recommendations with a calculated simple payback of $2,046 per year, a 73% reduction from the annual heating bill at the time. Another option - open to most homeowners - was to upgrade the house to Passivhaus standards for a 90% efficiency improvement. The family chose the latter.

Properly executed home improvements address the movement of heat air and moisture in a house. Failure to address all three can lead to problems. Insulating to retard heat loss does not air-tighten a house unless foam insulation is used. Old, air-leaky houses don't accumulate moisture because it escapes with the warm air that contains it, but in improperly tightened homes airborne moisture can get trapped inside structural elements (e.g walls), and causes mold, mildew and rot damage. The tighter a house the more pronounced the effects of weatherization mistakes, so it is important for home owners to understand the workings of a house. How else can they select knowledgeable contractors and see that improvements are executed correctly? In this period of transition from energy-wasting conventional building practices to greater energy-efficiency, even builders with decades of experience must climb a new learning curve.

The Northport cape couldn't be in better hands. Chris Corson, the homeowner, also owns and operates Ecocor Design/Build, based in Belfast, with several Passivhaus structures under their belt. Here are the steps Chris took to turn this half-century old house into a Passivhaus-level showcase of energy efficiency: He had a professional energy audit done, upgraded the insulation level of exterior walls, ceilings, and roof with densely packed cellulose, removed all the house- crowding vegetation, and stripped the house down to the exterior sheathing. He cut off the roof overhangs with a chain-saw, then seamlessly super-insulated the house from the outside, covering its walls and roof with a contiguous 5.5" thick layer of recycled polyisocyanurate foam board. Finally, to complete the super-insulation, Chris thermally isolated the basement from the heated envelope by sealing and insulating the basement ceiling. He also added a mud-room-inspired entryway and replaced all the original windows with Passivhaus-rated, triple-glazed, argon-filled windows with thermal bridge-free frames.

The result: a thermal-bridge-free, airtight, super-insulated building. To provide fresh air and remove excess moisture, heat recovery ventilation was installed. Outside the foam board "house-wrap", the whole building was covered with ice and water shield. Finally new siding of horizontal ship-lap boards was installed over 1x3" vertical nailing strips. Plans are to allow the exterior to weather and offset the natural-finished wood trim around the windows and doors.

Airtightness, tested with a blower door, improved from the original 5.05 to 0.65 ACH50, an 87% leakage reduction. Heating energy consumption was reduced by 90%, eliminating the need for any fossil fuel and reducing the household's carbon footprint from the original 15.7 lbs per ft2 of heated floor space per year to 3.7 lb/ft2/year, a 424% reduction. A pellet-fueled boiler takes care of the home's remaining space and water heating needs. It consumes less than a ton of wood pellets per year. In its original condition, this house would have burned about $4400 worth of oil this winter to heat water and keep the interior no warmer than 62°F. Instead, the fuel bill came to less than $240 for greater comfort at 68-70°F.

Cost to completion: $70,000. Projected savings in energy costs over the remaining mortgage period : $101,844. Return on investment 32%. An investment that keeps on giving. Beats a lot of others any day.