Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Your question is not clear enough. What is the paper about and what are you trying to describe about the climate? Are you trying to just compare the required heating and cooling potential? Then HDD and CDD are fairly decent and well accepted. You can find lots of data at http://www.degreedays.net/
If you want to succinctly discuss the effect on building design and overall energy including things like humidity, then I think talking about the ASHRAE climate zones is better (i.e. things like 2A, 4C, 7B, etc). These are more comprehensive, but coarse, distinctions. But, then you need to reference a paper that describes how these were determined rather than give an equation.
If you have a discussion of renewable energy in the paper, then neither describes the solar or wind potential at all and you would want another measure like average solar energy potential Wh/m^2/day.
| | 2 | No.2 Revision |
Your To answer your equation about the equation, your equation is correct except the standard definition uses the same number for the base and threshold i.e. you would do HDD12 or HDD20 not HDD20/12. You sum up the difference in temp between the base and the actual when the actual is above or below the base. You also need to use the average daily temp. Most calculators will actually do the sum on an hourly basis and then divide by 24 to get the daily numbers.
An important question is not clear enough. What is the paper about and to ask is what base do you want to use? Here in the US where we do it in Fahrenheight, typical numbers for building scientists are you trying to describe about the climate? Are you trying to just compare the required heating and cooling potential? Then HDD and CDD are fairly decent and well accepted. HDD50/CDD50 and HDD65/CDD65. There is a great online calculator at You can find lots of data at http://www.degreedays.net/
Your question about metric is not clear enough. What is the paper about and what are you trying to describe about the climate? Are you trying to just compare the required heating and cooling potential? Then HDD and CDD are fairly decent and well accepted.
If you want to succinctly discuss the effect on building design and overall energy including things like humidity, then I think talking about the ASHRAE climate zones is better (i.e. things like 2A, 4C, 7B, etc). These are more comprehensive, but coarse, distinctions. But, then you need to reference a paper that describes how these were determined rather than give an equation.
If you have a discussion of renewable energy in the paper, then neither describes the solar or wind potential at all and you would want another measure like average solar energy potential Wh/m^2/day.
| | 3 | No.3 Revision |
To answer your equation about the equation, your equation is correct except the standard definition uses the same number for the base and threshold i.e. you would do HDD12 or HDD20 not HDD20/12. You sum up the difference in temp temperature between the base and the actual when the actual is above or below the base. You also need to use the average daily temp. temperature. Most calculators will actually do the sum on an hourly basis and then divide by 24 to get the daily numbers.
An important question to ask is what base do you want to use? Here in the US where we do it in Fahrenheight, typical numbers for building scientists are HDD50/CDD50 and HDD65/CDD65. There is a great online calculator at You can find lots of data at http://www.degreedays.net/
Your question about metric is not clear enough. What is the paper about and what are you trying to describe about the climate? Are you trying to just compare the required heating and cooling potential? Then HDD and CDD are fairly decent and well accepted.
If you want to succinctly discuss the effect on building design and overall energy including things like humidity, then I think talking about the ASHRAE climate zones is better (i.e. things like 2A, 4C, 7B, etc). These are more comprehensive, but coarse, distinctions. But, then you need to reference a paper that describes how these were determined rather than give an equation.
If you have a discussion of renewable energy in the paper, then neither describes the solar or wind potential at all and you would want another measure like average solar energy potential Wh/m^2/day.
