Energy Report, February 2010

We still aren't living in the house and we're still keeping it heated in the low 60's using solar heat plus the electric backup heater. By the end of the month we had insulation in place over the door and window headers, and we had sealed some (but not yet all) of the openings around the doors where we were getting a lot of infiltration. We still had a lot of activity as contractors went in and out so the doors were opened quite often, and that contributed to our heat loss.


Average daily heating degree-days: 37.6
Average daily heating electricity used:* 48.2 kW h = 164,555 BTU
Average daily other electricity used: 9 kW h = 9823 BTU
Average daily solar heat collected: 11.0 kW h = 37,384 BTU
Heating electricity per degree-day: 1.28 kW h = 4376 BTU
Total heat (electric+solar) used per degree-day**: 1.42 kW h = 4850 BTU

* This includes only the electricity consumed by the electric backup heater.
** This is a measure of how well the house is insulated and sealed, and how much passive solar gain it collects.


Compared to January, this month was on average 2 degrees warmer and we had 13% less solar gain per day. Taking these factors into account, our average total heat (electric plus solar) used per degree day dropped by 16%. This indicates a significant improvement in the thermal envelope, which we attribute to finishing the missing insulation over the window and door headers and, more importantly we think, much less infiltration due to sealing gaps around the doors and windows. The net gain from these improvements was most likely higher than 16% because we also had less passive solar gain, which we cannot measure directly.

Although this month was much better than last month in terms of heat loss and electricity usage, we still don't consider it very good. We still have significant infiltration under some of the doors because we don't yet have the final door thresholds in place. We weren't in any hurry to seal up the gaps though, because the heat recovery ventilator was not yet installed so the infiltration was necessary for fresh air supply.

In the graph below you can see that we had some impressive daily heat gains near the middle of the month, with a couple of very sunny days in a row. But alas this is Michigan and sunny weather is not the norm for February so we had used up that heat within a week.


This page was updated on Wednesday January 11, 2017