Heat/cold degree days and Chill hours: Difference between revisions

Heat/cold degree days and Chill hours (view source)

Revision as of 20:29, 30 May 2013

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 ==Heat Degree Days==
 You may have a thermostat that makes your heating come on when the temperature falls below a threshold.
-Cumulus calculates an integration of the number of degrees below a threshold you select over the time that the temperature is below that threshold.
+Cumulus calculates an integration of the number of degrees below a threshold you select with the time that the temperature is below that threshold.
 Cumulus reports this by month as part of the National Oceanic and Atmospheric Administration (NOAA) style report, in the annual NOAA report, in dayfile.txt, and via heating degree days web tag. (NOAA is an Operating Unit of the U.S. Department of Commerce).
-If the threshold you select in Cumulus matches your thermostat, the reported value gives you a measure for how hard your heating system has worked; otherwise it is a statistic that gives you a feel for how cold it has been.
-So if for the whole of November, there was just one hour at one degree below the threshold, two hours at five degrees below, and three hours at seven degrees below; the total for the month would be (1*1)+(2*5) +(3*7) hours reported as 32 degree days.
+So if for the whole of November, there was four hours at one degree below the threshold, two hours at five degrees below, and three hours at seven degrees below; the total for the month would be (4*1)+(2*5) +(3*7) hours reported as 35 degree days.
+== Use of Heat Degree Days ==
+If you compare the heat degree days figure for two periods, then one would expect to have a higher heating bill in proportion to the increase in heat degree days.  Additionally, introducing energy efficent measures can only be evaluated if one makes allowance for the heat degree days before and after the new measures.
+Selecting the right threshold can be crucial, it might be as used by a thermostat to switch on the heating, or the planned comfort temperature. If the threshold you select in Cumulus matches your thermostat, the reported value gives you a measure for how hard your heating system has worked; otherwise it is a statistic that gives you a feel for how cold it has been.
 ==Chill Hours and/or Air Frost==