On energy analysis and BIM

While at the Building Science program at USC, an exciting thing that I discovered (apart from Revit itself!) was the integration of energy analysis functions within Revit in early 2007. IES, a well known building performance analysis tool, had incorporated some analysis functions within Revit MEP. The analysis itself was pretty basic - heating and cooling loads; but just its very inclusion meant that Revit was more than just a modeling/database tool. In fact, it was moving in the direction that Revit, as a Building Information Model, was supposed to….performing its role as a truly informative tool. Thanks to this feature(albeit a basic one), architects could take design decisions pertaining to energy efficiency earlier in the design, as opposed to relegating the task to MEP engineers after the design was done..(which simply doesn’t make sense!...what’s the point of analyzing a building for efficiency after the design has been frozen???)

In addition, IES also came out with a toolkit…essentially, you could export your Revit model into the toolkit and it was roll out some calculations for you…thermal loads as well as lighting loads. It also came with a neat little feature that estimated whether your building would qualify for LEED v2.2 Cr8: Daylight and Views.

Pretty exciting developments...except for some gaps. For example, Revit MEP comes with a drop down menu containing a list of walls, windows, roofs and floors that you could use for your analysis model.Revit takes values for the parameters associated with these components from their counterparts in IES, called the Apache Construction database. Unfortunately, what that means is that your analytical model, (apart from the actual geometry of the building) has very little to do with the building model itself...in other words, if you modeled a 6" timber frame wall, but selected, lets say, an 8" heavy weight concrete block, from the list, the program took the concrete block.

During a small experiment at SC, I discovered a slight discrepancy in the analysis results while testing a BIM model.I modeled a building, changed the thickness of the building fabric, kept the internal spatial volume the same and found that changing the thickness resulted in a different thermal load . This was pretty amazing, since this seemed to indicate that the wall thickness, at the very least, was being carried over for analysis!....till Mr Harriman at IES pointed out that the discrepancy was happening due to the increased external surface area(and therefore increased heat transfer etc)

For all the obvious gaps, I still think that have analysis embedded in your BIM model is a pretty neat idea and the industry certainly seems to be going in that direction....

Trick Tools

One of my favorite tools in Revit is the "Edit Cut Profile"...its a neat little "trick" tool that you'll appreciate all the more when deadlines are looming and tempers are frayed!

"Cut Profile" is a view specific editing tool, thats designed to make your life easier when you dont want to model the nuts and bolts...Case in point: the concrete foundation slab below is chamfered at the corners.Want to model it accurately?Think on the lines of in-place slab families,solid sweeps/extrusions....


But here's the thing...this profile is visible in ONLY one section view and a detaied callout.A quick and effective way to handle this situation(apart from modelling it,of course) is to use "Cut profile" on the foundation slab...here's how it works....

Use the Cut Profile "Face" option to select the slab face; and after Revit goes into the sketch mode(orange lines!) draft out your profile and finish the sketch. Make sure that your arrow points towards the part of the slab that should remain.
























Remember that this is view specific editing and will not show up in the model except inthe current view!

Modeling a Helix in Revit

It all starts with a helix…. I find that helixes are the most beautiful of all geometries, and it’s amazing how nature throws them at us time and time again; in the form of our DNA structure, the shape of a galaxy or even in the tendrils of a creeper plant. I absolutely love the unexpected ways one might come across helixes in architecture, from the ramp of the FLW’s Guggenheim, to the threads of a screw! Back in 2003-04, I used the helix in a column for a small residential building: I was fresh out of school, idealistic, and willing to push boundaries; the client was generous and open to exploration; it was a good combination. The resultant was a beautiful, rustic, helical brick column that became the defining point of the building. (as shown in the pic above and below)

Lately, I explored whether Revit could model helixes effectively, and the answer is, it can…but in pieces. What is surprising is that it’s much easier to model a helix in CAD, they even have a command for it! (and they say, BIM is supposed to make our life easier!)
For creating the helix shown, I created a “swept blend” solid in a generic model based family file. I sketched a semicircle as its path, and circles of the same radius as its profiles; the trick is to offset the second profile a certain distance from the path;the distance would depend upon how high/deep you would like to your helix strand to go.(This step is easy when you know how,and annoying and frustrating when you don’t)

Create one helix half at a time, and when both are done, simply copy paste in elevation view.
Voila!You have the helix…enjoy!