We’re finally done! The home looks great, and is already performing better than expected. We are anxiously awaiting the Home Energy Rating Score (HERS) and other stats, which we will share as soon as they available. Some preliminary data is showing a HERS below 50, with total annual operating costs under $900. This is more than 50% more efficient than the 2006 energy code. There is no cross-reference yet from the HERS to the newest (2015) energy code, but the home is at least 10-15% more energy efficient than that code, which went into effect only a few weeks ago. The image below shows the HERS scale.
Other preliminary data that we have so far is showing that heating will represent less than 25% of the home’s energy usage, and water heating only about 15%. The largest energy usage of the home is the lights and appliances. We installed all LED lights and Energy Star appliances, so there isn’t much more we can do to reduce that number. It just shows how little energy the home itself costs to run by being built with energy conservation in mind.
Another benefit of the tight, well insulated home is comfort. I was in the home doing a final inspection of the work and filling out paperwork last week for about an hour. In that time the furnace never came on, and it was 25 degrees outside. The thermostat read 64 degrees, but I was comfortable in short sleeves because there was absolutely no draft. Since air movement in a home can lead to a significant difference in how a temperature feels to us, that 64 degrees felt just fine.
As part of our final testing of the home by our third-party energy rater, a blower door test was performed to test the air-tightness of the home. A fan and frame are placed in an entry door and the fan is turned on to blow outwards, which simulates a 20 mph wind on all sides of the home. Anywhere air can leak into the home is tested with a smoke stick, and in this home we almost couldn’t find any visible leakage whatsoever. The cubic feet per minute (cfm) of air moving through the fan to maintain a certain vacuum pressure in the home gives you the leakage of the home. For those of you interested in numbers, the home tested at just over 200 cfm at a negative pressure of 50 Pascals. This was our best test on any home to date by far. The image below shows a standard blower door (not from our home).
For those of you who are more visual, a standard existing home has an air leakage that represents a small window being left open year-round, and a newer home something the size of a doggy-door, or maybe a mail slot. Our home’s air leakage could be represented by a 1-1/4″ diameter hole. Since air leakage accounts for about 40% of a home’s energy loss, all of this results in very low energy bills and operating costs for our homeowners, now and even more in the future as energy prices inevitably rise.
We’ll be holding a dedication ceremony this coming Sunday for the family, volunteers, and community, and the family should be moving in sometime toward the end of the month.
Stay tuned for more information as the final results come in from our rater!