Why analysis period doesn't affect the HVAC sizing values?

Hi Chris,

I deleted my previous post and I would like to ask only about the design day for the HVAC sizing. In the example file, the simulation run for January and I have noticed that the HVAC sizing values are still the same if the analysis is run for the entire year, the extreme cold week, or the extreme hot week. Shouldn’t the analysis period/ design day affect the HVAC sizing values?


@MohammedAlshayeb ,

The sizing calculation that E+ runs is completely separate from the annual simulation. In fact, the sizing calculation does not even use the .epw file and only uses the information in the .ddy file (I’d recommend opening this file in a text editor to see the data that is being used). So changing the analysis period won’t have any effect on the results of the sizing run.

The original methods for sizing HVAC systems with design days comes from ASHRAE Fundamentals and this is the method that most mechanical engineers use (whether it’s through EnergyPlus, Trane Trace, or even just hand/excel calculations). This section of the EnergyPlus Engineering reference will give you more information about the methods being used:


1 Like

Thank you @chris for the clarification. It is clear now !