clima HDD calculation

For Bologna, I do not think our results match the climate.onebuilding results.

HDD for 10°C baseline with our tool = 730 HDD for 10°C baseline Onebuilding = 673

Sep 07 '21 06:09 FedericoTartarini

@FedericoTartarini Hi Federico, to verify that Bologna's HDD calculations were accurate. I went to Climate.OneBuilding. Org, downloaded the Bologna EPW and opened the CBE Clima tool and uploaded this EPW file and I calculated the total HDD results. Then, on this CBE Clima tool, I selected the Bologna EPW file and again calculated the results for the total HDD. I compared these two results and found them both to be the same. I would like to check with you if this has been solved, thanks!

Apr 10 '23 10:04 Ericlee0128

I apologize for not making this 100% clear, but unfortunately, this is not the issue I was mentioning.

The issue is that if you open the .zip climateorg file you downloaded with from here, inside there is a file with ends with stat (ITA_ER_Bologna-Marconi.AP.161400_TMYx.stat).

Open this file with either NotePad or Excel you will find a table in it showing the heating degree day.

This is the value that does not match the results of the Clima tool. Please let me know if this is clear now.

Apr 11 '23 03:04 FedericoTartarini

I apologize for not making this 100% clear, but unfortunately, this is not the issue I was mentioning. The issue is that if you open the .zip climateorg file you downloaded with from here, inside there is a file with ends with stat (ITA_ER_Bologna-Marconi.AP.161400_TMYx.stat). Open this file with either NotePad or Excel you will find a table in it showing the heating degree day. This is the value that does not match the results of the Clima tool. Please let me know if this is clear now.

Hi Federico, thanks for the explanation, I misunderstood it a bit before. I would like to double check, I noticed that the STAT file has two HDDs "Monthly Standard Heating/Cooling Degree Days/Hours" and "Monthly Weather File Heating/Cooling Degree Days/Hours", which one should I use. Thanks!

Apr 11 '23 05:04 Ericlee0128

Very good point. Thank you for noticing this. I do not know what is the difference between the two. It would be amazing if you could look into it and let me know if you find the reason they provide to sets of values.

Apr 11 '23 06:04 FedericoTartarini

I believe there are two HDD value sets based on the following which is stipulated in the stat file. The "Monthly Standard Heating/Cooling Degree Days/Hours" values are being calculated off the 2021 ASHRAE design conditions.

Where as the "Monthly Weather File Heating/Cooling Degree Days/Hours" HDD values are solely calculated off the weather data source.

Apr 12 '23 20:04 danielh7-cs9

Great, so I then believe we should compare our results with the Monthly Weather File Heating since we only have access to this dataset.

Apr 13 '23 02:04 FedericoTartarini

Hey @FedericoTartarini, Eric and I have been wrapping our heads around quite a bit, but so far are unable to identify where the calculation error may be with the clima code:

I've researched but I am unable to ascertain the formula climate.onebuilding is using to calculate the HDD and CDD values.

Apr 18 '23 00:04 danielh7-cs9

Thank you for looking into this. @giobetti shall we contact Dru and ask him if he knows how these values are calculated in the OneBuilding files?

Apr 18 '23 00:04 FedericoTartarini

Thank you for looking into this. @giobetti shall we contact Dru and ask him if he knows how these values are calculated in the OneBuilding files?

Hi Federico, just checking if you've received any response here?

May 02 '23 10:05 danielh7-cs9

No unfortunately.

May 03 '23 02:05 FedericoTartarini