Our office building is placed in Copenhagen, Denmark. Our question is which climate zone to use? Is it zone 5, zone 6 or can we use either one of those? - We are using a simulation Tool (IES-VE) which automatically suggests zone 6 as soon as Copenhagen is picked as location. - However, according to the ASHRAE Standard 90.1-2007 table B-4 for international climate zone definitions we land in zone 5 with a HDD65F of 6288 hours.
No you don't get to pick one. If you are using the 90.1 baseline then you need to use the climate zone assignment from 90.1. It sounds like IES-VE is in error assuming your 6288 is correct. You might want to ask them why it is showing up in their software as a zone 6. Perhaps they have different HDD65F data?