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Old 11-30-10, 03:04 AM   #48
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This weekend I finally downloaded heating degree day data for my area. I then took my gas usage, calculated (from the summer) how much we need per day for hot water & cooking, subtracted that from the winter per day gas usage, divided by HDD and got a more or less stable ratio - between 0.5 and 0.9 m3/hdd, mostly between 0.6 and 0.7. I guess it depends on many things: what temperature I kept the house at, outdoor wind, how much cooking or electrical load we had (that adds heat to the house), etc., but a season average can be somehow made out. I guess this is what I'll be comparing, winter to winter, to see if renovations had any impact. This is also how we could compare the houses in the ER energy tracker: (winter kWh - summer kWh)/hdd. Maybe that could also be a function of the house's area?

That number would be like a car's fuel economy - it would should how much energy is needed for certain tasks, but it would be possible to aim for reducing it, either through ecorenovations, or more efficient use (lowering the temperature, for example). I also calculated my sister-in-law's m3/hdd ratio and it was 20-30% more than our's. Their house is not only larger, but they also don't play with the temperature settings as aggressively as I do - their furnace is on more often then our's, even though they are hardly ever at home.
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