Accuracy of Shadow Studies

[lhanyok]

We have a project where we're required to provide a shadow study to the state to prove that the building's shadows won't hit a certain point. I know how to use the shadow and sun studies in Revit, but the project manager is concerned about the accuracy, especially since its dealing with the government. Can anyone vouch for the accuracy?

[sbrown]

If you pick the correct location and orientation for your project they are very accurate. do a quick test with a box and your sun charts but they are very accurate.

[truevis]

Attached are a photo and montage with Revit shadows. Compare the shadows -- especially the tall lamp post. I knew when & where I took the original picture so set Revit as close as I could.

You could do your own comparison of real life and Revit shadows. Remember to set True North.

[trombe]

Hello lhanyok.

I had the same question in the last couple of years since the tools became available in Revit.
In NZ we are always having to do sunlight analysis it seems, as part of what is known locally as resource consent applications, and for which breaches of sunlight access planes / recession planes are the most common and normal thing during planning.

It is not my neck on the line, in your country, however, I would like to endorse the images of the author below.
My own test was the following:
I accessed 2 x A1 landscape format sheets each for half of the solar year from a friendly planner at the local building consent authority (was then known as territorial authority and also as the local city council).

These 2 sheets comprehensively detailed the time, altitudes and azimuths for the whole year down to the minute almost. They were prepared on contract by a commercial structural / civil engineer and look as for all the normal presentations of the type.

I had already done loads of prep work on the resource consent application and was looking to confirm how accurate Revit really is in these matters, for similar reasons to your own.
I did not want to be faced with lawyers, Engineers, Architects or anyone else who had specialist knowledge, and find that my conclusions were not correct because the base material was in fact wrong.

I painstakingly plotted the data from the sheets of the sun charts onto my Revit outputs and was very happy and delighted to see that the results matched as precisely as I could tell with each other - eg shadows overlaid matched precisely for a range of times of the day and of the year with what Revit predicted.

So from my own perspective, I have absolute confidence that anything I produce in Revit can withstand any scrutiny from any specialist or a lawyer so long as, you have set things up correctly.

I am quite wary of some of these things because the implications of what can happen to me if I get it wrong are scary and we have still got 1 year to 18 months before design licensing becomes mandatory in NZ and you go on a public register into the bargain.

I really think the best test is to match hard data (as above) against Revit prediction and once you have seen the results, you will move forward with confidence.

good luck
trombe












We have a project where we're required to provide a shadow study to the state to prove that the building's shadows won't hit a certain point. I know how to use the shadow and sun studies in Revit, but the project manager is concerned about the accuracy, especially since its dealing with the government. Can anyone vouch for the accuracy?