Overconstrains in a Parametric Window

I'm experiencing some difficulties trying to create a simple window with two sliding panels. I need to create one parameter to set the window height from the reference level (2,1m), and another for contro11ing the window's sill (with a range between 0,9m to 1,1m). Very simple, but in Revit it brings some further complication.

The standard Height parameter only moves the upper reference plane, leaving a 0,80m sill. An aligned dimension linking the upper plane to the reference level with a custom parameter (Janela_Altura = 2,1m) doesn't work as Revit pop-ups a message: Labeling this dimension would overconstrain the sketch. I don't understand why such a simple model can't have this labelled dimension! http://www.revitforum.org/images/smi...m/banghead.gif


Any advice will be very useful.
Thanks in advance

Hi, Bruno. Welcome to posting on the forum.

The Revit template for a window has two built-in parameters that affect the height: Height (type parameter) and Default Sill Height (instance parameter). Height + Default Sill Height = Head Height. If you try to create a parameter for the Head Height, from the Ref. Level to the top, it will over constrain the family because of the equation I wrote. You can't tell Revit to change the Head Height and not change the Height or Default Sill Height, so there is a conflict. Revit won't know which one to change.

From Revit's window template, you cannot delete the Height or Default Sill Height parameters. But when you buy a window, you usually want to know how big it is. Then when you install it, you want to know how high off the ground (the sill) you want to put it. Doing the math (or looking in the Revit properties window) to figure out the head height is pretty easy.

That said, if you really want to control Sill Height and Head Height and the height of the window is secondary, you could create a Generic Wall-Hosted family and make it a window. Then you have complete control over all parameters. hope that all helps!