Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

12-month load calculation in EnergyPlus

asked 2016-04-01 19:45:39 -0600

updated 2016-08-24 11:15:59 -0600

From a recent conversation on load sizing here:

"1. Trace700 usually will run all 12 cooling design months and so it may happen that a zone does not peak in same month as the summer design OADB and this may be due to a higher solar component in the off month. So I always recommend, whether running Trace or E+, to run all 12 months for cooling design."

This seems to be a common reason for differences in cooling design sizing between Trace and OpenStudio/EnergyPlus.

The solution is to add in 'SummerDesignDay' 'SizingPeriod:DesignDay' objects for each month. From what I can tell, most .ddy files packaged with the TMY3 datasets include 'SizingPeriod:DesignDay' objects for only 1 month for heating and 1 month for cooling.

12 month design day data are available

So it's possible to do a 12-month cooling design load calc by taking the 12-month data, finding the appropriate 'SizingPeriod:DesignDay' objects for the site, copying them over to the .ddy file, and then reimporting that into OpenStudio.

It's a bit tedious.

Does anyone know if there is a .ddy dataset available online that includes 12-month 'SizingPeriod:DesignDay' objects for TMY3 locations?

EDIT: is a website that shows a map of ASHRAE design day data. No .ddy capability, but still very useful.

edit retag flag offensive close merge delete


I downloaded the 12 month design day from the link but it has the same days information than the .ddy file.

obuchely gravatar imageobuchely ( 2016-09-12 15:04:12 -0600 )edit

2 Answers

Sort by ยป oldest newest most voted

answered 2016-04-03 06:04:10 -0600

I don't know of a .ddy dataset and I haven't looked for it (I'm assuming you've searched online prior to posting).

But it'll be very easy to create... The link you gave has .imf file. It's basically a collection of the SizingPeriod:DesignDay objects encompassed in if statements.

##ifdef KEY
SizingPeriod:DesignDay (1st for the location)
SizingPeriod:DesignDay (12th for the location)
SizingPeriod:DesignDay (1st for the location)
SizingPeriod:DesignDay (12th for the location)

The key can be found in the csv file.

So if you need a couple locations, do it manually.

Otherwise, you can write something that'll parse it out and save as individual files in 10 or less lines of code.

edit flag offensive delete link more



Thanks. I guess I'll settle for manually now. If someone does parse it out, perhaps they can host it on @Mostapha Roudsari's epwmap page.

mdahlhausen gravatar imagemdahlhausen ( 2016-04-04 11:32:51 -0600 )edit

answered 2016-04-02 09:56:39 -0600

Not to my knowledge of ddy file includes 12 months design conditions. But monthly design conditions are available in ASHRAE handbook and can be added manually into the OS.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools



Asked: 2016-04-01 19:45:39 -0600

Seen: 327 times

Last updated: Aug 24 '16