1:5:10:365 EcoTip Blog

December 9, 2008

:344 Calculating Daily HDD

Take the 1:5:10:365 challenge: Do one thing – for 5 to 10 minutes – 365 days a year to make our home and planet environment better.

1:5:10:344 EcoTip: Heating degree days are a calculated number that is used to help quantify those periods of time where the outside temperature is cold enough for heating to be necessary for the building to be comfortable. The bigger the number – the more energy that will need to be consumed to warm the building.

The calculation can be complicated since temperatures can vary quite dramatically throughout a day. A simplified way to estimate Heating Degree Days is to determine the average temperature for the day (add the high and low temperature together then divide that number by two). If the average for the day is 65 degrees F – or higher your home won’t require heating and there are no heating degree days that day. If the number is less than 65 degrees F, then subtract it from 65. The answer will give you an approximation of that day’s heating degree day number. 


 Additional Information:

Suggested Review: :343

As an example, if the high temperature for the day is 55 and the low temperature is 35, then the average temperature is 45. Subtracting 45 from 65 would result in 20 HDD for that day. Adding the HDD for each day in the month would give you the HDD for that month.

As I said before – this is oversimplified. Tomorrow’s tip will be a web-site that can be used to calculate this for you much more accurately.

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