Room Area and Curtain Walls

Let’s take a look at a little known fact about computed room area when curtain walls are used. Below is a rectangular room with 4 basic walls. The Interior Fill subcategory under the Rooms category was checked to make the room area visible in a light cyan tint. In this case the area is calculated at the wall finish.

However Curtain Walls don’t have a “finish”; they just have a location line. So when using curtain walls that go all the way to the floor, area is computed up to the location line.

What does this mean? If you’re not aware of this fact, there’s a good chance your room area is overestimated. Personally I think putting the location line at the exterior (you have to specify mullion and panel offsets to move the location line to the desired location) makes a lot of sense from a modeling standpoint as you usually know the exterior line of your building. However that is the worst thing you can do for room area calculations, especially with thick curtain walls. So your options are:

1. Make the curtain wall Non-Room Bounding and draw in room separation lines where you need them (in the above example you would sketch them on the inside face). Now you can place your location line wherever you want.
2. Set your location line to the interior face of the curtain wall and leave it as Room Bounding.

My personal preference is #2 because most users forget and won’t bother sketching in room separation lines. Do I like how this particular aspect of curtain walls works? Nope, but I’ll deal with it!

Room Area and Curtain Walls