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?

Five Minutes of Phasing

Here's another short video in the "Five Minutes of" theme. This time I decided to delve into the basics of phasing. Due in part to the recurring assumption that I see where people feel it is necessary to add a "demo" phase. I wrote about this in the past. It's a natural assumption but not necessary for Revit's process and features to work. You can watch it at OpEd Videos or You Tube...or here.

Demo Is Not a Phase

At least in Revit's "world".

This is a common point of confusion when people start using Revit phasing tools, real versus virtual, Revit's "reality" versus real "reality".

Demo is not a phase in "Revit land". It's a phase in "People land" because people do demolition things before some other construction things. Revit however considers demolition to occur during the new work. You have an existing building and then do new work...demolition is no different from erecting a new wall to Revit. The phasing tool is focused on showing things graphically not how we "people" think of managing our construction tasks. I can do demolition in one room while someone is painting a wall in another.

[Edited 8/16/2011] After a couple of emails I decided to alter this post a bit. To restate my initial premise:

Revit does not require a separate phase for demolition in order for the phase filters and graphic overrides to work.

It is possible to add a demolition phase and keep things in order. It can be confusing though to be sure the elements are modeled in the correct views, using the correct phase and phase filter settings. The more complex the requirements are for showing the contrasting phases of work are the more peculiar things can get.

Future Phases

Revit has four states relative to phases, New, Existing, Temporary and Demolished. There is no future state. What can you do if you want to indicate where the future phase work will be located?

Overlay views on sheets!

It is a simple matter to create a view whose phase is assigned to the Future phase and tell Revit through Phase Filters that you don’t want to see Existing, Temporary or Demolished elements. The building you draw in this future phase will look new. If you don’t want it to you can use visibility graphics overrides to make it look different or even much simpler.

As long as the scale of the views you need to overlay on the sheet are the same you’ll find that Revit will snap them into alignment. Here is a simplistic representation of all the phases on a sheet in two views overlaid.


This example is one that has a different overrides applied.


This is the Future phased view setup to put on a sheet.


If you look closely I've used the Linework tool to make a small wall that will be demolished between the New and Future work look like it is to be demolished.

Give er a try?

Phased by Your Exports?

When you export your project to dwg files do they lack the reference to the phases of your project? The default dwg/dgn export files do not include the information that Revit needs to specify the layers according to phase. It just so happens that there is a Autodesk Knowledge Base article that explains how to resolve this. If you want to search yourself, try the words "phase export" to get a link to the article. Too tired to click the link? Here's the text from the site:

Issue

You want to know how Demo, Existing, New, and Temporary layers are included when a file is exported to DWG and DGN.

Solution

The default export files, Layers-dgn-AIA.txt and exportLayers-dwg-AIA.txt, do not include appendices for -DEMO, -EXIST, -NEWW, or -TEMP layers for demolished, existing, new, and temporary objects in the model.

These definitions can be added to the templates by adding the following lines to the exportlayers-dwg-AIA.txt file (located in the Data directory):

Demolished -DEMO -DEMO
Existing -EXST -EXST
New -NEWW -NEWW
Temporary -TEMP -TEMP

The following lines can be added to the exportlayers-dgn-AIA.txt file (also located in the Data directory):

Demolished 50 1 50 1 -DEMO -DEMO
Existing 51 1 51 1 -EXIST -EXIST
New 54 1 54 1 -NEWW -NEWW
Temporary 58 1 58 1 -TEMP -TEMP

You can download [Link: RF111d01.txt] exportlayers-dwg-AIA.txt and/or [Link: RF111d02.txt] exportlayers-dgn-AIA.txt and copy them to your [Revit_install_directory]/Data directory.

Sorry you'll have to visit the site to get the files. The date published for this article says 20060405 but I know that I read it earlier than that this year, perhaps it's been modified? I seem to recall it being a couple years old.