Revit MEP heating and cooling load

[Anonymous]

Hi all,

How can i use my own building model elements (walls, roofs...) in heating and cooling load calculation at schematic type section. Revit has already defined some. Will the override check box works?

Please kindly let me know.

[Anonymous]

I think Revit does not have this option .....

[hmunsell · Accepted solution]

what version of Revit are you using?

i'm not sure when this was introduced...

• open the Energy Settings
• pick the Other Options > Edit... button
• Under Material Thermal Properties, check the Detailed Elements option
  • this will use the thermal properties in the bounding elements IF they have thermal material property assigned.

https://help.autodesk.com/view/RVT/2021/ENU/?guid=GUID-3C378374-D360-4207-A558-3500922A452E

[Anonymous]

 ahmedshawki60PR7ME Thank you sir. 

[Anonymous]

hmunsell I'm using the 2020 version. The way you suggested has worked. Thank you sir

[hmunsell]

my pleasure.... glad i could assist. 

[iainsavage]

@hmunsell, I was of the same opinion as you but I've just tested this in a project and the Detailed Elements tick box has no effect on my results for Heating and Cooling loads analysis.

The only thing which has effect is either changing the conceptual masses or changing the schematic types and ticking the Override boxes.

This however is limited by the constructions in Revit (I know you can change these by editing an external file but its a PITA) and also means the values are applied globally across the whole project.

My project is part 19th century existing and part new build with very variable u-values (stone walls at u=1.4 W/m2k, new walls at 0.15 W/m2k) so the results are nonsense (and I've wasted half a day creating and applying the correct actual construction types).

I can only assume that the Detailed Elements tick box only works in the Energy Analysis tool or in Insight rather than in Heating & Cooling loads.

I would be better exporting the fabric element areas to an excel file and doing my own calculations or maybe I can do it with calculated parameters in Revit- the results would be far more accurate.

Just thought I should share this for anyone else who might be caught out by this.

[hmunsell]

Interesting, the way its supposed to work, at least in 2021, is:

When you use multiple methods to specify material thermal properties, they are applied in the following order:

1. Conceptual types are the default.
2. Schematic types, where enabled, override conceptual types.
3. Detailed elements, where enabled and where material thermal properties are specified for building elements, override both conceptual types and schematic types.

The Detail elements are supposed to override Conceptual and Schematic types IF the building elements have thermal properties assigned to there materials. if the building elements don't have thermal property's it would use the Conceptual and Schematic types instead. 

[iainsavage]

That’s what I thought too but I now think this is only for Energy Analysis and not for the Heating & Cooling loads tool - it is also interesting that when you access energy settings from within the heating & cooling loads tool the advanced options  including the Detailed Elements tick box don’t appear, they are only available if you go into the energy settings directly from the ribbon.

I’m now starting to agree with others like @HVAC-Novice that this aspect of Revit is simply not good enough and potentially dangerous if relied upon for design.

I’d be really happy to be proved wrong though since I’m trying to work wholly within Revit without relying on secondary software. 

[iainsavage]

Okay, so I've spent a while researching this further and found the Autodesk "help" topics to be rather unclear on the topic. They also seem to muddle up references to the Heating & Cooling Loads calculation tool...

... with the HVAC Systems Loads and Sizing calculation in the Systems Analysis tool..

which adds to the confusion.

After some trial and error though I conclude that the Detailed Elements check box has no effect on the results of the Heating & Cooling Loads tool BUT the actual construction elements are used in the calculation if the following options are used:-

1. do not check the overrides boxes in the schematic types dialogue
2. select "Use Conceptual Masses and Building Elements" option in the Energy Settings dialogue

With these settings IF actual construction elements with thermal properties are present then these will be used, if they are not then the conceptual masses will be used instead. Detailed Elements check box has no effect.

To prove this I created a test project with two spaces, identical except for the type of construction elements and applied some tests the results of which are below.

One thing to note is that the results from the Systems Analysis tool are significantly different from those obtained by the Heating & Cooling Loads tool but I haven't had time to explore this deviation.

I would now be relatively happy to use this Heating & Cooling Loads tool with some more confidence but bearing in mind that it does not, for inexplicable reasons, calculate heatloss through the floor.