Several years ago, I wrote a post about the value of an Energy Audit.
The story behind that audit was one side. Improved Comfort. This time it is about the other side. Decreased Cost of Operation.
An home energy audit reviews the ability of your home to retain the heated air from your HVAC System in the winter and the cooled air in the summer. The best metaphor I’ve seen is to compare the Thermal Enclosure to a Bucket of Water. The picture above is a good example. The hose is like the HVAC System. It fills the house with hot air in the winter and cool air in the summer. The Bucket allows the conditioned to leave the home.
The result of the energy audit is to prioritize which holes to fix first, second and third. Some of this is about how big a thermal leak the hole is, and some of this is about cost.
Attics are less costly to insulate than walls. There is room for more insulation, it is not a lengthy process, and there is nothing like patching holes after you have insulated.
This home had the improvements made as recommended by the audit, in February 2012. The energy usage for 36 months prior to and now 36 months after the improvements is now available.
The 3 year average for annual energy use before the improvements is 34,972 KWH.
The 3 year average for annual energy use after the improvements is 18,940 KWH.
A decrease of 45% in energy used. The bills are paid in dollars, so why refer to an energy measure. Using energy measures means future increases in Utility Rates are not considered. Will those increases happen? Yes! Not counting on them is important. Did they happen during this 6 year period. Yes, several times. So the results are about actual savings.
Here is Brian, blowing insulation into the walls. The walls before the work started were uninsulated. If this home had been stucco or brick, this step would not have been cost effective. The material is cellulose, providing an R-13 in the wall. Cellulose is easy to install in this application. This crew had done this many times and the experience is worth a lot.
The image on the right is the attic. As you can see there is a little insulation in there before work started. That meant the crew could do the air sealing first. Fibrous insulation like the rock wool you see, or the cellulose that was added, does not stop air movement. Warm air from inside easily goes up into the attic and outside. Good crews air seal before they insulate. They are already up there. A caulking gun is not hard to carry along. See those wires, the electrician drilled a one inch hole to put the wire through. Lots of air leakage.
Here is a picture I took last winter. New snow the night before on the roof of this house. Note the hole near the edge of the roof in the snow cover. That hole in the snow is right over the outside wall and there is a light switch, or outlet on the wall below it.