MEP_Level of Detail_Workflow

[brane1012]

Hi All,

I am wondering what are your experiences with Level Of Detail in MEP installations. For example, BIM Forum LOD Specification states following:

2.4 Example – Light Fixture:
• 100 cost/sf attached to floor slabs
• 200 light fixture, generic/approximate size/shape/location
• 300 Design specified 2x4 troffer, specific size/shape/location
• 350 Actual model, Lightolier DPA2G12LS232, specific size/shape/location
• 400 As 350, plus special mounting details, as in a decorative soffit

How do you deal with that in real world modelling?

1. Do you have one lighting fixture family for LOD 200 (same family for all lamps because is approximate size)?
2. Do you have multiple lighting fixture families for LOD 300 (multiple because specific size)?
3. Do you have multiple manufacturer lighting fixture families for LOD 350?

Do you have separate families based on LOD and change them all between LOD phases, or how do you deal with that?

Best regards, Branimir

[txelwood]

You would not have different families for different LODs.

Usually for lighting, you would have a family for 2x2s,2x4s,1x4s, etc. You would then have instances or "fixture types" for each different light within those lights. So maybe you have (3) types of 2x4s as in type GL1, GL2, GL3, etc.. Each light type gets tagged and is associated with a fixture schedule that has the rest of the light fixture details.

[josephpeel]

100-200 You could probably just include a parameter in the space/room that says what kind of lighting will be used in the room (LOI rather than LOD..)
300 Generic, non manufacturer specific 'Light Fixture' family. Use types for different standard sizes and symbols rather than loads of separate families (Set this with Type parameters). Specify power, output etc in parameters.
350+ An actual manufacturer model for 3D, or a generic fixture with the same size and the product specified in parameters. Actual performance specification in parameters.

In general keep your families super simple, unless you actually need to make rendered visualisations. Add detail by adding information instead.

[brane1012]

100-200 You could probably just include a parameter in the space/room that says what kind of lighting will be used in the room (LOI rather than LOD..)
300 Generic, non manufacturer specific 'Light Fixture' family. Use types for different standard sizes and symbols rather than loads of separate families (Set this with Type parameters). Specify power, output etc in parameters.
350+ An actual manufacturer model for 3D, or a generic fixture with the same size and the product specified in parameters. Actual performance specification in parameters.

In general keep your families super simple, unless you actually need to make rendered visualisations. Add detail by adding information instead.

Does that mean that I need to change all families between LOD 300 and LOD 350? Isn't that time consuming?

[snowyweston]

My advice?

Disregard "350" completely.

"350" is an imaginary (LOD) state imagined up by people who know they can't ask for 400 but want more than 300 but won't pay for the difference.

[Twiceroadsfool]

My advice? Ignore LOD completely. Have a productive conversation with the owner/client about what needs to be in the model when its delivered, and when they need it in the model.

The entire concept of "LOD stages" is (just my humble opinion) complete horseshit.

[Alex Page]

I always think of LOD dates as when you can rely on the information as stated in the LOD .
So we dont swap out families for LOD purposes, we just ensure that the information within the family is correct at the dates as explained in the BIM execution plans so others can rely on our information.
We swap out families just for our internal processes (i.e. when correct lighting family has been specified)

[jamiew]

I agree with Alex Page. LOD = percentage of family parameters filled in. Switching out a family late in design, especially one from a manufacturer, is going to create problems. There's a good chance it is not hosted/positioned the same way, and will have different parameters than the families already scheduled.

[wildirish317]

Speaking from a mechanical contractor's pov, the design model should either have a generic representation, or the basis of design family. We typically are under contract to coordinate "in 3d" with other trades, and this coordination is more for the pipes, duct, and conduit that connect the families than the families themselves; although this changes when we enter mechanical and electrical equipment rooms.

My general rule of thumb is "keep things as simple as you can while still providing the desired result".

When we get into spooling pipe assemblies, we then move into LOD=400, as we are fabricating pieces in the shop to be assembled on-site.