Phasing and Replacement Windows

Over the years people have often complained about trying to document replacing existing windows with modern windows but maintaining the existing opening. This means swapping windows with families that are the exact same size. This is related to the wall that Revit creates to infill a wall that has a demolished window. You may have encountered this warning message?

That message appeared when I attempted to place new windows in the New Construction phase after demolishing the existing windows first. I was careful to set up views assigned to different phases and phase filters so there wouldn't be any display conflicts.

I got interested in this issue again recently because of a thread at the Autodesk User Forums for Revit Architecture. A fellow member was sharing how much trouble Revit has been giving them trying to do this kind of work. After some back and forth I narrowed it down to one window family and another member realized that family uses a void to cut the hosting wall in the family itself versus the usual opening.

This led me to write some hypotheses for testing purposes. I wrote:

Hypothesis A: Within phasing we can replace Existing Window A with New replacement Window B using the exact same sizes (same size opening dimensions) IF they both use an OPENING in the family to cut the host.

Hypothesis B: Within phasing we can replace Existing Window A with New replacement Window B using the exact same sizes (same size opening dimensions) IF they both use a VOID in the family to cut the host.

If either of the above are false then...

Hypothesis C: Within phasing we CANNOT replace Existing Window A with New replacement Window B using the exact same sizes (same size opening dimensions) IF one uses an OPENING and the other uses a VOID, in the family, to cut the host.

I did some testing using the latest release of Revit, 2024.1 and I determined the following:

Hypothesis A is TRUE

Hypothesis B is FALSE

Hypothesis C is neither

I find that I can replace a Void based window with an Opening based window but not the reverse. Also any alterations to the hosting wall in the project; such as length adjustment, or top/bottom offsets, attach/detach will place the void type window at risk of being deleted. Weirder still is that it might not delete all of them, one or more.

It seems that the short answer is: eliminate window families that use a void to cut the hosting wall IF you intend to place identical sized windows in phased projects; to demonstrate existing window replacement without altering the existing openings. Windows created this way will not work for this task. A logical next hypothesis is to anticipate similar behavior in door families.

I speculate that this warning happens because an opening cuts fully through the host while a void (or combination of voids) might cut more and/or less of the host as it travels through it. I suspect that the infill wall can't abide the shape a void might create and that in turn means a void won't be viable as a window to alter the location of the infill wall. I think it's similar to curtain walls only supporting non-rectilinear panels with the system panel families.

I'd love to hear that the developers will test this against their own experience and expectations. I know that a lot of people rely on voids to shape the opening in a host wall to match a variety of actual construction techniques for openings. To eliminate voids in families as an option for this kind of project (replacement windows (and doors?)) is not ideal. They'd probably have to revisit the entire logic of infill elements where demolished hosted elements occur. Perhaps leave it up to us to fill in holes?

Wall Openings and Room Area

Fwiw, I wrote these related posts: this one in 2005 and this one in 2006. This is ONE Too, it's about creating openings when we use Copy/Monitor (it's still not a good idea unfortunately).

A recent thread at RFO started off by asking which method is best to create openings in walls. There are a few options: Family (like a door, window or generic model opening family), Wall Opening, Wall > Edit Profile, Automatically Embed feature of Curtain Walls or even an in-place wall with a void.

Like anything understanding their differences is important. For example if I need a round hole in a wall I could use a jigsaw, sawzall, Xacto knife, sledgehammer, hole saw, drill bit etc (or dynamite). Depending on the size of the hole I need any of those could provide a hole with varying degrees of accuracy, success and effort.

Revit's Wall Openings, apart from being a bit weird to use, affect room bounding differently than other techniques that cut a wall. In the attached image:

• Left side of Image: a Wall Opening doesn't respect (alters/affects) the bounding nature of the dividing wall and using Edit Profile affects room bounding of the wall too
• Center of Image: a opening family does respect the wall's room bounding
• Right side of Image: A wall opening allows area to extend "into" a host wall where a curtain wall needs to go while a curtain wall (top wall) that uses Automatically Embed (bottom wall) instead does not
• Added image (right image) shows same conditions but with using Edit Profile on the wall in the left side of the image

Here's what the model looks like in 3D, the view range cut plane for the plan view above is the typical 4'-0" (1200mm ish). If the wall opening comes into contact with the Computation Height of the host level it "affects" the room bounding. Added a wall opening (like a window) to the middle building.

By the way for trivia fans, Jeff Hanson (Autodesk SME, User Experience) wrote: "... the wall opening tool was created specifically for creating a wall opening in a wall that is curved in plan. There is no way to edit the profile of a wall curved in plan..."

Added this image in response to a comment from Rob (1/3/2017). I used Edit Profile and Wall Opening to create the openings and then placed Room Separators to decide which room should get the area between them.

Floor Perimeter

When you examine the properties of a floor you'll find Perimeter. Somebody decided perimeter shouldn't be available to tags so we can't tag a floor but we can see it in schedule (no, can't tag it in 2014 either).

If you alter a floor sketch to define an opening for something like for a stair or a mechanical chase, it alters the perimeter calculation. If you use either a Shaft Opening or Opening by Face it doesn't alter the perimeter value. Floor A is untouched, B is altered within the sketch and C has two openings one of each type. You'll see in the schedule that perimeter is not altered except where the floor sketch is changed to create the opening.

The moral of the story? If you'd like to be able to use the floor slab perimeter value then don't edit the floor sketch to create openings.

Party Wall Doors

You know the doors that are in hotels that pass between rooms. They make it easy to rent two rooms side by side, one for kids, one for the parents...or co-workers traveling to a meeting etc. I got a question via email asking how to approach this. The issue expressed was that Revit won't let you put two doors on top of each other. They want to list two doors in the schedule (one for each side) so the more or less obvious solution of showing both panels and swings in one family didn't cut it.

One solution is to edit the door family and eliminate the Opening element and replace it with a void instead. This allows you to adjust the depth of the void so it only cuts one half of the shared wall. Place two doors and align them...voila, done. If you make this an instance parameter driven option your regular single flush door type could pull double duty, cutting all the way through a wall or only half way.

Another approach could be a single family that uses two nested (and Shared) families. The door could be assigned to the Generic Model category so the assembly doesn't schedule in a door schedule, the nested shared doors (assigned to the door category) do instead. Alternatively the category could be assigned to doors too but you'd either have to filter out the assembly or the individual doors because you'd have an "extra" door.

Whatever solution we use we do have to consider how "we" schedule doors and how the product is dealt with by a manufacturer. Since the frame has to built to accomodate two panels it might actually be better or correct to create a single door family that just happens to have two panels. Everything is a bit trickier the deeper you look at the question, at least when you aren't just concerned with what a door looks like in a plan view drawing.

Dept. of Subtle - Opening Transparent in Elevation or 3D

Quick one tonight. The opening element in window families is designed to offer either transparent or opaque behavior when seen in elevation/section views. Normally we like to "see" through glass in 3D views so we can see inside the building. In elevation/section views however seeing the "innards" of the building might be really confusing to the reader. This subtle setting determines how the opening should behave in either condition.

If you want to see through your openings in elevation, check the option for Elevation. It's usually not checked which is why you can't see through them. If you'd rather obscure them in a 3D view to then remove the check for 3D.

In the past we couldn't have more than one Opening element in a single family so we often removed them and used a void instead. I find in 2011 and 2012 that Revit doesn't mind multiple openings in the family. You can't however have a void and an Opening in the same family, one or the other. To be more accurate you CAN create a void but you'll get this message if you try to CUT the host with the void.