Air Infiltration Advice
Air infiltration is the leading cause of energy loss in homes, according to the U.S. Department of Energy, accounting for between 25% and 40% of lost energy.
Consequently, carefully detailing the building envelope is of utmost importance. In fact, building science experts who understand the amazingly complex nature of vapor pressure, moisture diffusion and the like, recommend what they call a “belt and suspenders” approach, which means two lines of defense against air leakage.
For example, Amaris Custom Homes makes a point of taping the seams on the exterior wall’s structural insulated sheathing, and gluing all the wood-to-wood connections. Then for the second layer of protection, interior cavities are sprayed with closed-cell foam.
“We also use closed-cell insulation in the attic ceiling to a depth of around 2”, and then use fiberglass from there,” says Pruban. “We make sure the foam wraps from the ceiling deck, up to the wind washing and up to the roof air shoots to seal any side air leakage. We then extend the SIS up to the roof air shoots on the exterior for our wind washing. Once sprayed from the attic, there is one continuous closed-cell foam barrier from ceiling deck to roof air shoots.”
MECHANICAL VENTILATION UPDATE
As exhaust air enters the insulated energy recovery ventilation unit, a heat-exchanging mechanism extracts the waste heat in the winter, or the cooling energy in the summer, and transfers it to the incoming air.
With conventional heating and cooling systems accounting for close to half of an average home’s energy use, according to the U.S. Energy Information Administration, obviously, the biggest impact on the bottom line can be made through efficient HVAC equipment.
Consequently, energy recovery systems, also known as heat recovery ventilation (HRV) systems, are becoming increasingly popular.
In fact, Tom Reid, owner, Green Home Construction, Hood River, Ore., considers HRVs to be indispensible. “Because we build tight, we need to ventilate right, so HRVs are installed on every house we build.”
“These systems are continuously bringing the fresh air in from a place with good air quality and at the same time, exhausting the stale air from the house,” explains Miloš Jovanović, co-founder Root Design Build, Portland, Ore. “The heat exchanger preheats the cold incoming air with very little energy and provides ultimately healthy air at low cost.”
The real magic lies within the system’s ability to capture about 70% of the heat latent in the stale, outgoing air and then transfer it to the fresh, incoming air stream.
Although the process itself is highly efficient, older systems formerly required a lot of juice to operate. Fortunately, technological advancements have taken down these units from 100 watts to just 30 watts.
“The controls have also improved considerable over the years, giving homeowners more control over their indoor environment,” relates Mark Wahl, co-owner, Cobblestone Homes, Saginaw, Mich. “They can now more closely control their indoor relative humidity along with the temperature.”
10.2011
33
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68