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

Severe error caused by Controller Mechanical Ventilation (OpenStudio 1.5.0)

asked 2014-11-25 15:31:47 -0500

updated 2017-05-17 12:27:23 -0500

Dear All,

I have a problem when simulating a very simple building using Sketchup Make and OpenStudio 1.5.0.

I created two OS spaces in Skethup and didn't use "Set Attributes for Selected Spaces" (I plan to complete this part in OS). Then I launged OS, created two thermal zones and assigned the two spaces to thermal zones seperately. After adding thermostat, space type (I used '189.1-2009-Office-Whole Building -Md Office' in library which includes people, load, outdoor air ...), I added the 'Packaged Rooftop VAV with Reheat' system to the model and didn't change any default numbers. Finally, the two thermal zones were connected to the demand side of the air loop.

However, when I clicked the simulation bottom, two errors stopped the simulation:


I exported idf file and used E+ to check it, and it seems in the component 'Controller:MechanicalVentilation', the "Zone 1 Name""Design Specification Outdoor Air Object Name 1""Design Specification Zone Air Distribution Object Name" are missing. No one "DesignSpecification:ZoneAirDistribution" item is created.

Actually I didn't have this problem using previous OS and Sketchup version. Is there anything I miss when creating the model? Anyone has the same problem before? Thanks.

Best wishes,


edit retag flag offensive close merge delete


I met the same problem,but I can't make sure if I was missing design day,can you tell me how to check?

Done's avatar Done  ( 2017-02-28 01:43:22 -0500 )edit

@Done, in the "site" tab, if you could see a few design days uploaded (showing design day name, day of month etc.), that means the file includes design day (OS 1.13)

Yan's avatar Yan  ( 2017-02-28 13:06:31 -0500 )edit

3 Answers

Sort by ยป oldest newest most voted

answered 2014-11-26 09:12:01 -0500

updated 2014-11-26 09:12:33 -0500

5 possible causes of Controller:MechanicalVentilation errors that I've run across:

  1. The model is missing design days. You can check the text "Number of Design Days:" field on the Weather File & Design Days tab. The design days get imported into the .osm when you browse for and select a file, so don't worry if the file path is empty after you reopen the file as long as the "Number of Design Days:" is more than 0.
  2. The model has an Airloop with no OA intake system, but one or more of the zones connected to this Airloop has a DesignSpecificationOutdoorAir object.
  3. The model has an Airloop with an OA intake system, but none of the zones connected to the Airloop have a DesignSpecificationOutdoorAir object.
  4. The Airloop is connected to a zone that contains no spaces, and therefore has no DesignSpecificationOutdoorAir object.
  5. The model has an Airloop with no zones attached.
edit flag offensive delete link more



Thanks! Actually I found it does results from Missing Design Days! It's interesting that the error didn't mention missing design day but just lost controller Mechanical Ventilation!

Yan's avatar Yan  ( 2014-11-26 09:19:16 -0500 )edit

It appears when switching any equipment after running a model the equipment no longer being specified is being retained in the idf file and expects to be connected. Ideal Air loads is telling me I need to specify node connections and controls. This does not make sense to me. Matt

MattStewart's avatar MattStewart  ( 2014-12-30 11:55:10 -0500 )edit

Some DDY files downloaded from the EERE website (aka "") do not actually contain any design day information (e.g., Boulder/Broomfield, CO TMY3). If this is the case, the path will be empty and "Number of Design Days" will still be zero after browsing to the DDY file. If this is the case, select a different DDY file from a nearby location.

Neal Kruis's avatar Neal Kruis  ( 2015-06-02 15:46:46 -0500 )edit

I know this is an old post but I am having the same problem and it seems like it's what @MattStewart mentions in his comment. I define a new HVAC system, connect zones and the model runs. Then I switch a VFD fan to a constant flow fan and the simulation crashes. Then switch back to original VFD and simulation crashes again which means that the problem lies on removing defined components in the .idf file. Is there a way around it? I will try to manually remove the previous definition from the .idf file and see what happens.

dsfakianakis's avatar dsfakianakis  ( 2015-11-04 10:29:26 -0500 )edit

Quick update: Apparently if I remove the VFD and then add another fan the simulation crashes. But if I add another fan and then remove the existing VFD the simulation executes perfectly. I guess openstudio does not like it if I leave the system with no fan even for a second.

dsfakianakis's avatar dsfakianakis  ( 2015-11-04 10:40:03 -0500 )edit

answered 2016-12-06 11:22:38 -0500

Also, in my case I found out if you forgot to assign a space type for the zone,the same error would appear as well.

edit flag offensive delete link more

answered 2014-11-25 16:28:42 -0500

Not sure if this is the issue, but if you have an air loop with an outdoor air object on it, make sure that at least one of the zones on that air loop has an design specification outdoor air object, even if it is set to 0. That used to create the error you are seeing, but there could also be other causes.

edit flag offensive delete link more


Thanks for your reply. I checked every zone, each of them has Design Specification Outdoor Air object. I defined the Design Specification Outdoor Air in Space Type and assign space type to each zone. I think maybe there is other causes.

Yan's avatar Yan  ( 2014-11-26 08:10:02 -0500 )edit

I have the same errors re-occurring. I felt that I could run the model with Ideal Air but V1.5 wants me to assign a zone to equipment. So I thought I might need to delete the equipment and this is not allowed. The error encountered when attempting to delete PTAC and Heatpump not being used is ["Unhandled Exception"] Access violation - no RTTI data!

MattStewart's avatar MattStewart  ( 2014-12-30 10:27:36 -0500 )edit

Your Answer

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

Add Answer

Training Workshops


Question Tools



Asked: 2014-11-25 15:31:47 -0500

Seen: 3,936 times

Last updated: Dec 06 '16