Creating green roofs in Revit

[rob.goetze]

I read the Green Roofs posting http://forums.augi.com/showthread.php?t=23176&highlight=green+roof with interest. However, it did not discuss how to create such roofs in Revit.

In our demos of Revit (I work for an Autodesk reseller), we often talk about how it can help with sustainable design, pointing out features like the sun studies, the material takeoffs to document percentage of recycled materials, etc. With some municipalities (including the city of Chicago) encouraging green roofs with incentives of various sorts, Revit should work effectively with green roofs.

I was working on one and found that the layer functions and priorities, while useful for regular roofs, are not very amenable to green roofs. I used a sample from greenroofs.net (see attached) as the basis for my trial roof.

There are several membrane-type layers which, according to Revit, cannot have thickness. However, it seems that the membrane layers on the green roof, such as the filter membrane, do indeed require thickness. There is a drainage layer, which I was not sure how to categorize (I would have used membrane, but had to end up using Thermal/Air). And there was a support panel -- seemingly similar to Substrate (2) -- but Revit didn't like that as the result was the layer function priorities being in the "wrong order". I used the Finish (4) and Finish (5) layers for the earth and the grass (so that it renders properly...) without Revit complaining.

I've attached an image which shows some of the errors which Revit gave me after I laid out the layers in a (semi-) reasonable way.

If anyone out there finds that Revit's current roof tool is adequately suited for designing green roofs, I'd like to hear more about how you would do it.

If, on the other hand, the roof tool is not suited for green roofs, I'd like to request that the factory improve this!


Rob Goetze
IMAGINiT Technologies

[Scott D Davis]

Just make the "membrane" layers of the roof that require thickness into a Finish(4) or Finish(5) type instead. This "layering" is really just for how Revit handles the cleanup of similar materials. I wouldn't be so literal in the interpretation of a "membrane" layer in this dialog box.

[ron.sanpedro]

Just make the "membrane" layers of the roof that require thickness into a Finish(4) or Finish(5) type instead. This "layering" is really just for how Revit handles the cleanup of similar materials. I wouldn't be so literal in the interpretation of a "membrane" layer in this dialog box.

My concern there is that in general Revit does use the same vocabulary as architects, and this is a great strength. Given that a Finish is, pretty much by definition, an exposed material, using Finish in this context is "exactly wrong" and thus something better off avoided, lest it lead to confusion down the road. Of course calling it a membrane is perhaps not right either, as well as just not possible given the zero thickness issue.
In this case I would use a Substrate located outside the Core for all the drainage layers and such. I do the same thing for the nail up drainage mat that you can put behind a wall finish for a poor man's rain screen wall. While this stuff is not truly a substrate, it is more like a substrate than a finish. It is also kind of a membrane, but it having thickness it can't go there. Substrate seems like the best answer.
That said, I may actually run into problems with that decision at some point, and have to change it to a finish, but I hope not!

Best,
Gordon

[cphubb]

Gorden,

The type of layer does not affect anything but the layering order and the ability to cleanup. If you are using material or keynote tags you may notice that membrane layers are not taggable. We have removed all of them and replaced them with substrate layers that have very small thickness numbers, trying to mimic the actual thickness of the material. They will then tag just fine and there appears to be no other ramifications to this method. The only real hard part about the roof above is ordering the layers properly and making the grass look like grass and not GWB or something.

[ron.sanpedro]

Gorden,

The type of layer does not affect anything but the layering order and the ability to cleanup. If you are using material or keynote tags you may notice that membrane layers are not taggable. We have removed all of them and replaced them with substrate layers that have very small thickness numbers, trying to mimic the actual thickness of the material. They will then tag just fine and there appears to be no other ramifications to this method. The only real hard part about the roof above is ordering the layers properly and making the grass look like grass and not GWB or something.

My worry from a training standpoint is, I don't want to have to explain to a very busy architect that Finish means "this" in the real world, and "that" in Revit, and Membrane means..., and Substrate means... I would rather see Revit use architectural language correctly and consistently (it is "purpose built" after all), and allow us to do such crazy zany things as tag a membrane material, or document a green roof, or whatever. ;)

As for the grass, I will be playing with this tonight actually, and I suspect I will include all the "constructed" stuff in the roof familiy, but leave the soil layer to be modeled using site tools. Phil Read's boulder example from AU makes me thing that I should be able to put a little site up there, and mound it up in the middle for drainage, or whatever. We shall see.

Best,
Gordon

[rob.goetze]

I agree, Gordon, that Revit should use architectural language correctly and consistently, and that even membrane layers should be taggable. In Revit Structure, the roof object has been modified by the addition of a "structural decking" layer which will allow the user to pick a profile. No reason why Revit roofs couldn't be modified overall, to accommodate green roofs -- I think this would enhance the product and its "showability" in a demo context.

Hadn't thought of modelling the earth/grass using the site tools. That's an interesting idea, though I can see that there are times one might want the general site and topography turned off while still seeing a green roof...


Rob

[ron.sanpedro]

I agree, Gordon, that Revit should use architectural language correctly and consistently, and that even membrane layers should be taggable. In Revit Structure, the roof object has been modified by the addition of a "structural decking" layer which will allow the user to pick a profile. No reason why Revit roofs couldn't be modified overall, to accommodate green roofs -- I think this would enhance the product and its "showability" in a demo context.

Hadn't thought of modelling the earth/grass using the site tools. That's an interesting idea, though I can see that there are times one might want the general site and topography turned off while still seeing a green roof...


Rob

I really wish the approach Autodesk was taking was that everything is shared Graphically, and individual products where more about the Analytical aspects. As an Architect, I NEED to show structural decking, and duct work, and beams that miter, etc. I don't need to do structural analysis on things, or air flow calcs, or the like. But I very much need the graphic. The fact that the Structural tool has things that an Architect needs but the Building tool doesn't have seems odd, especially given that all the Revit based products are essentially the same thing under the hood. Would it really be that hard to give us ALL the modeling tools in ALL the packages, and admit that the differentiation is appropriate elsewhere? I suspect that

As for the second point, you could quickly add a Name or Comment to the topo surfaces on the roof and filter by that. I had hoped to be able to use a different material (anyone have a Sedum hatch ;)) and filter by that, but no such luck. I hope someday Filters will work with intrinsic aspects of an object as well as the text fields.

Best,
Gordon

[cphubb]

Gordon, Rob,
Realize that there is no "Architectural" language that is universal or even nation or state wide. Revit is using terms that comply to the standards being set by the BIM industry and generally are matched by the other BIM software manufactures. We have also gotten some blow back on this particularly on Curtain Walls that are storefront or some other panelized system. What would you call them? As to the membrane layers vs finish try the other alternative. Layer 1 ??? Layer 2??? Layer 3?? How about A-Wall-Patt?

People will need to learn something new and if they cannot they will not succeed in this brave new world. The terminology works very well for people learning the software and process, they understand what a membrane layer is they only need to know it cannot have thickness. A little knowledge goes a long way.

[rob.goetze]

Realize that there is no "Architectural" language that is universal or even nation or state wide. Revit is using terms that comply to the standards being set by the BIM industry and generally are matched by the other BIM software manufactures. [snip]

People will need to learn something new and if they cannot they will not succeed in this brave new world. The terminology works very well for people learning the software and process, they understand what a membrane layer is they only need to know it cannot have thickness. A little knowledge goes a long way.

Chris:

So if I understand you correctly, as there is no agreed upon architectural language, an architect should adjust his/her work to comply with the standards being set by the BIM industry? I'm curious to know whether these are worldwide BIM industry standards, or perhaps based on BIM software manufacturers in the U.S.?

You also say people need to learn something new.... It seems to me that in North America, we're learning about something new called green roofs -- not new historically or at a global level, but newer in terms of us applying them to commercial buildings and the like.
It doesn't take much bravery to learn about them... though it would be nice if leading edge software such as Autodesk Revit would "learn something new" too, rather than obliging me to fit green roofs into limited ideas as to how roofs are structured. You do call them roofs where you're from, don't you? Or do you have a different word for such things? :-)

And why shouldn't membrane layers have thickness? I realize that often membranes have a negligible thickness, but they must have some thickness -- and in some cases (like green roofs) membranes have a lot of thickness. If Revit is going to be true to its claim to BIM -- then I should be able to Model membranes which have thickness.

I vote for for adding green roof-related layer choices to the Roof tool to accommodate the drainage layer, filter membrane, etc. I'm not content to work around this by calling everything a substrate or a finish.

[Kevin Janik]

Chris:

So if I understand you correctly, as there is no agreed upon architectural language, an architect should adjust his/her work to comply with the standards being set by the BIM industry? I'm curious to know whether these are worldwide BIM industry standards, or perhaps based on BIM software manufacturers in the U.S.?

You also say people need to learn something new.... It seems to me that in North America, we're learning about something new called green roofs -- not new historically or at a global level, but newer in terms of us applying them to commercial buildings and the like.
It doesn't take much bravery to learn about them... though it would be nice if leading edge software such as Autodesk Revit would "learn something new" too, rather than obliging me to fit green roofs into limited ideas as to how roofs are structured. You do call them roofs where you're from, don't you? Or do you have a different word for such things? :-)

And why shouldn't membrane layers have thickness? I realize that often membranes have a negligible thickness, but they must have some thickness -- and in some cases (like green roofs) membranes have a lot of thickness. If Revit is going to be true to its claim to BIM -- then I should be able to Model membranes which have thickness.

I vote for for adding green roof-related layer choices to the Roof tool to accommodate the drainage layer, filter membrane, etc. I'm not content to work around this by calling everything a substrate or a finish.

If the terminology was appropriate in BIM to describe architectural elements, then perhaps the learning of BIM for interns would be a learning of correct terminology for architecture and all this variation from one area of the country to another would be reduced.

Just an idea.

Kevin

[Scott D Davis]

In some other architectural programs, you use "slabs" to draw everything from roofs to walls to actual slab on grades. Sometimes you must learn what layers, display reps, xrefs, paperspace, modelspace, multi-view blocks, PC3 files, property set definitions, aecobjectexplode, navigator, sheet set manager, PGP files, aecscheduledatabase, tables, lisp routines, CTBa, STBs, mass elements, trimming by fence, dimstyles, palettes, refedit, attedit, cmddia, filedia, body modifiers, osnaps, and many, many more are.

In this case, its just a mtter of knowing that in a Revit Wall, the membrane layer wil always have 0 thickness, and will clean up with other membrane layers. Its a way of describing those items in a wall aseembly which really do not contribute to the size of the assembly. Anything else must be categorized by Finish 1, finish 2, Substrate, structure, or theraml/air.

In other words, the "language" of Revit is much closer to the language of architecture than some of the alternatives.

[ron.sanpedro]

In other words, the "language" of Revit is much closer to the language of architecture than some of the alternatives.

Scott,
I agree, and there lies the rub. When your goal is to do the architecture, and learning the tool is just a side task, then having the "language" in the software parallel the language in the real world is a HUGE aid in learning. As long as you don't have too many deviations. This is one of the areas where Revit beats ADT by a light year. And because it is so good at working and speaking like we do, it is that much more of a stubbed toe kind of pain when it doesn't. With ADT and AutoCAD we just got used to it, but I would rather not see Revit start down that road. I don't want to "get used to" things that Revit doesn't do right yet. I want it to get better and do more things right. More than once I have had people who thought they understood Revit language because it was word for word Architectural language, and then made mistakes because in this case Revit was actually speaking something else entirely, but using the exact same words. And there is NOTHING to let the user know that they didn't understand, other than the fact that something that should have worked didn't.
Personally I think the fact that you can't tag a membrane layer is a much bigger problem. If I put it in the model, I am going to have to tell the contractor to put it in the building, so I need to tag it. But that said, in the real world a membrane CAN have thickness, and telling someone to ID a membrane (which is called a membrane in the specs, and which performs like a membrane as defined by the dictionary, and which is referred to as a membrane by every person involved with the construction process) as a substrate because Revit doesn't actually understand a membrane with thickness, is a real problem. Revit NEEDS to be right. Yes, I can come up with a workaround, yes I can train everyone, yes I can use a dumb tag, but why do I HAVE to. Would it not be easier for the Factory to just change the Membrane to act like every other component of a wall, where it has thickness (allow a 0 thickness, by all means) and can be tagged and just works? I think adding a Drainage layer would be useful too, not just in Green Roofs, but in Rain Screen walls, and perhaps in Slab on Grade floors. Hey, a wall style for Foundations with a 2" Drainage layer that adjusts independently, so you can stop it below grade. Cool! ;)

My $0.02 anyway.

Best,
Gordon

[Steve_Stafford]

I find some of this discussion amusing. No offense intended but I find it interesting that we are arguing the merits of including a thickness for the membrane layer in a Revit wall/roof.

Just a short while ago you could start a serious argument in a firm by suggesting that your dwg linework should represent the actual thickness of a wall system instead of the nominal thickness, or vice versa.

As my friend Cyril Verley says, "It's all good!". That we are having this discussion is good. That it is related to the software we design with is good!

Still can't help but wonder if we were using AutoCAD, would we be having this conversation?

Just me sticking my nose in where t'weren't asked...

Oh, for green roofs I'd be inclined to have two roof objects, one or structure and one for "finish" (turf). This would give me additional control over the extent of the grass apart from the structure and the roof edges involved. I'd do this for spanish tile roofs as well or cold roof systems.

Remember, the way Revit works now is all based on assumptions and decisions made by the designers/engineers in the past. Decisions that made sense then sometimes don't seem as sound much later. Just as the design process in architecture tends to force us to revisit some of our assumptions and decisions, so too must the Revit product team. So prioritization and action become the difficult tasks.

[ron.sanpedro]

Still can't help but wonder if we were using AutoCAD, would we be having this conversation?



If we where doing this in AutoCAD we wouldn't be talking about green roofs because we would be wasting so much time DRAFTING that we wouldn't have any budget left to do sustainable design! ;) And I am only partially joking.
But I do think it is worth remembering that we gripe about relatively small things for the simple fact that Revit gets all the big things RIGHT! The major stuff left to improve on is stuff that in AutoCAD was simply trivial, or so far from even remotely possible that we just gave up hoping. In all ways Revit has raised the bar.
And as you say, the way Revit works now is based on assumptions, like membranes never have thickness. Well, we have established that in the real world membranes (materials with desirable qualities if selective permeability) can and do have thickness. So hopefully a later version of Revit will address that and we can move on to complaining about Revit not making modular sheet layout ala NCS as easy as we might like. ;) Or not being able to override or append text in a dimension as I want (yes, I NEED \X in Revit!)

Best,
Gordon

[brakware]

Something that I have noticed in a lot of discussions, even besides this one, is that people will look for the explicit answer. The power of Revit, to me, is the ability to find the custom answer. My first project on Revit has involved me having to make a great deal of custom family elements for a specialized type of architecture (animal holding buildings for zoos). In that I saw the power of the custom family and custom tagging.

It would be nice if Revit had every possible architectural element embedded into it so that we could just pick from a list of infinite possibilities, but it cannot. Instead of the roof elements and layers being called out from the onset, I think that a better approach for the Revit design team would be to make the roof structure a list of layers (layer 1, layer 2, etc.) that have a variable thickness, always. Each layer should be taggable, regardless of thickness, and the layers can be labelled whatever you want. For a green roof, make a layer that is X inches thick, label it a "membrane," choose a fill pattern, tag it in the detail, and list it in the schedule.

If the user were calling out what it was rather than Revit calling out what it was, then we could keep our office standards. It could still have some basic structure names embedded (label according to a list: substrate, structure, membrane, etc.), but also it should allow custom layer names (drainage membrane, fill, etc.) to be added to that list.

There is my $0.02... I would rather see an increase in customizability than some minor adjustments to the un-editable lists that Revit keeps.

[amara]

I think one way to expand the graphic representation of membrane and other layers which usually are not represented in drawings, such as for example plaster layers, is to be able to add them in the structure of the wall or slab, but to get them to display only in fine detail drawing. A check box could be added where each layer can have the option to show or not show at certain detail levels, or at scales coarser than ...
I think the most important part of this is that this way all such components can be included in material takeoff schedules. Currently the area of such items as paint or plaster need to be manually calculated from other items.

Charles

[ron.sanpedro]

I think one way to expand the graphic representation of membrane and other layers which usually are not represented in drawings, such as for example plaster layers, is to be able to add them in the structure of the wall or slab, but to get them to display only in fine detail drawing. A check box could be added where each layer can have the option to show or not show at certain detail levels, or at scales coarser than ...
I think the most important part of this is that this way all such components can be included in material takeoff schedules. Currently the area of such items as paint or plaster need to be manually calculated from other items.

Charles

This would also address being able to do a Framing Plan where finishes are not even shown. I also like to idea of materials having the same Detail Level toggle on hatches. I want my gyp to show up in Medium detail, but I certainly don't want the hatch there in a 1/8" view. But in a 1/2" detail I would like to see the material. Even better would be multiple hatches per material. Paint P1 could be an RGB solid in Fine Detail, but a diagonal hatch in Medium Detail. P2 is a different RGB solid in Fine, and a diagonal cross hatch in Medium. Now I can do an interior elevation at Fine Detail for presentations and the same interior elevation at Medium Detail for CDs. Woo hoo!

Best,
Gordon

[Phil Read]

Hi Rob -

I think you'd be better off trying to make the roof in two passes. This type of roof will not necessarily cover the entire "roof" area. If there are areas of the roof which are not vegetated (likely) then you'll need two Roof Types anyway. But "vertical" divisions (where you have sketches adjacent to each other) between roof types can be tricky.

I'd suggest different types based on a "horizontal" approach. So one roof for the structural resolution (from the structural support layer to the waterproof layer) which would be fairly ubiquitous. Then another type based on the vegetated areas (drainage to vegetation).

You should be able to "Join Geometry" and the line between the two types in Section will go away.

One advantage to this approach is that you can change the structural thickness in one pass (rather than have to go to multiple types). Another advantage is that if the vegetated areas need to be modified, you won't need to modify two sketches - since the division between roofs is horizontal.

All the best -

Phil

[ejburrell67787]

Just saw this thread and thought I'd add my 2p. When I last modeled a green roof in Revit (v6 / 6.1 I think) I did it as two roofs - a structural roof with a green roof build-up on top (as Phil Read suggests). I placed what in reality are membranes on a substrate layer so that they could be where I wanted them and have some thickness. While I was stuck showing them as 5mm thick it did mean when I did details there was actually space to indicate the membranes! (Think traditional draughting dashed lines...) I added the sedum layer in the details by using a repeat detail (brought in from a manufacturer's autocad detail from memory).

Think I might have posted the image before but here it is again anyway!