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Heat loss through basement wall / semi exposed basement

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Message 1 of 3
HVAC-Novice
1818 Views, 2 Replies

Heat loss through basement wall / semi exposed basement

I have a building with basement where grade line is about half height. So my heat loss consists of 2 parts:

- through wall to outside air via the upper haf of the wall

- through he wall and ground (and through slab)

 

when I model that in Revit and accurately tell that grade level is grade level (in project settings/energy settings), Revit only seems to show the floor as ground-bounding. the only way around seesm to be to have 2 spaces in the same room. For example with 10' wall and grade line at 5', space 1 would be 5'high, and space 2 would be 5'high.

 

Now I realize the load calculation in Revit seems to be more a guestimator. I export via gbXML to TraneTrace. When I create just one space, Trace recognizes that exactly the way I see it in Revit (all walls to outdoor air, only slab to ground). So far so bad.

But when I use my split-space method, Trace basically sees that as 2 rooms: room 1 only exposed half height to outseide, room too only exposed to ground half height and the slab. I called up Trane support if there is a way to unite the 2 rooms, but there isn't. The support staff knew about the problem and indicated someone (likely at Revit end) is working on a workaround.

 

The dimensions of the rooms seem to have been correct, the insulation values most definitely not. I just modeled a few adjacent spaces and it seems in Trace it looks like

 

Does  anyone have an idea on if I can create a space in revit that accurately gives me the exposed and non-exposed basement wall portion without having to create 2 spaces? I hope 2013 version will correct this...

 

My next problem I just realized while trying this out: when I have multiple rooms with adjacent spaces, it seems when exporting to gbXML every wall is treated like an adjacent space and shows up in Trace as such. In addition windows and doors don't seem to be exported to Trace. Am I doing something wrong?

 

I started this project out wanting to do the load calculation in Revit, and then in Trace to compare. At a minimum I wanted to get the room/window dimensions transferred. But it seems the load calcualtion and gbXML export doesn't work at all (at least not when you want correct data)

Revit version: R2024.2
2 REPLIES 2
Message 2 of 3
Chris.Aquino
in reply to: HVAC-Novice

The Heating and Cooling Loads tool uses the Ground Plane setting in Project Information > Energy Settings to specify the level that serves as the ground level reference for the building. Surfaces below this level are considered underground. So in this case you will need to create two spaces, one below the grade, and one at/above grade.

We understand that this may not be the preferred workflow, but the permanent fix for this issue would require that the code for Revit be modified. Because this issue has just been logged, there is no specific timeline for when any fix may be released. If an update is released, I would review the accompanying documentation to see if this fix is included.

If you would like this functionality to change, this link is setup for you to submit feature requests, or feedback, directly to our Development group.

I encourage you to use the feedback link as our Development group is always interested and would like to hear your feedback directly, since you are better suited to state the business case for a feature request.



Chris Aquino
Adoption Marketing Manager | BIM Collaborate Pro
@Aquinotecture

Message 3 of 3
fredULB
in reply to: Chris.Aquino

Hello,

 

any news about this problem?

 

It is still impossible to have the heat loss through the floor with REVIT 2015.

 

Best regards

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