Revit cryptic knowledge – what is the “R” field at the end of the “in-canvas tooltip”?

You all know very well “in-canvas tooltips”, although you may not be aware of this official name, which I found in Revit online help. In-canvas tooltips are yellowish tags, which are displayed next to the cursor when it detects (and highlights) an object in the Drawing/Modeling Area. They provide very useful information about the detected object – its Category, Family and Type.

In canvas tooltip

When you work work with Worksets and use Options two more fields appear at the beginning of the tooltip information – Option Set:Option and Workset – as on the above image. But sometimes there is one more mysterious component at the very end of this information chain – after the Type name. It is R followed by an integer number, like on the image below (R1 in this case).

In canvas tooltip with R

Ever wondered what the hell it is? Me to… After having searched the web in vain, I gave up and wrote an e-mail to my contact, who works somewhere deep in Autodesk. He must have pretty high security clearence, because after having contacted someone even deeper (he had no idea himself) he sent me an answer …

The R+integer is thermal resistance of a building element, a piece of data, which comes from Thermal Resistance type property under Analytical Properties of a Revit family (system or component). Analytical Properties can be enabled for component families (like Windows), when their Analytical Construction is set to something else than <none>, but for some system families (like Roofs), it looks like they are hard coded. What is even more interesting is that the number after R is always rounded up or down to an integer.

At first I was quite happy having solved this mystery, but then I realized that the values of thermal resistance of are usually rather small numbers, often less than 1 and in Autodesk Analytical Properties are quoted with a precision of four decimal digits. So I asked my contact some further questions:

  • Why was this particular coefficient given the privilege to be included in the in-canvas tooltip tag in Revit? This tag provides information about the name and place of the object in Revit organizational structure (Option:Workset:Category:Family:Type) rather than lists its physical properties. And, by the way, for windows the U-value is a more often used coefficient …
  • Why is the R value so ridiculously rounded up? This very fact makes it completely useless. Thermal resistance in Analytical Constructions is given with the precision of four decimal places and most types of glazing have the value less than 0.5 resulting in the same value of 0 in the tag for all of them …
  • Wouldn’t it be better just to remove it rather than make people scratch their heads over something what is useless even for those privileged few who know what it is?

I am looking forward to some answers from deep inside Autodesk.

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