Is there a proper name for combo unit of 2 windows side-by-side?

la_koalaOctober 10, 2010

Hi, my apologies if this is a stupid question. While I am a home owner with pretty good math skills, I don't know if I'm thinking about this in the appropriate way.

I'd like to use the right terminology for this (makes my Google searches more accurate and I can talk to contractors and make sense. :-)

Is there a proper term to use when talking about having two double-hung windows side-by-side in a single rough opening?

The basic situation is I have an existing double-hung window (daylight opening 29 1/2" wide) and am planning on remodeling that wall and I want to put in two double-hungs side-by-side.

How is the rough opening calculated in that "combo" scenario?

I mean, I can look up the manufacturer's tables for what the rough opening width is for one double-hung with a given daylight opening width. For example, the Marvin Clad Ultimate Double-Hung conversion table says to add 7 7/16" width to the daylight opening width.

But for a side-by-side combo of two, do the manufacturers have tables for these, or is there some standard for the width of the middle section between the two windows? Or are two windows side-by-side really two frames together, and the frame width of the "combo" equals 2 times the frame of one window?

Feel free to tell me if my questions don't make sense. I'm here to learn.


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Mulled is the term I am familiar with.

    Bookmark   October 10, 2010 at 7:20PM
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Hi dallasauburn, thanks so much! When I use "mulled window" in Google, I actually get hits to pages that talk about this, and it sounds just like what I want to do.


    Bookmark   October 10, 2010 at 9:59PM
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Twin Double hung would the proper descriptor for what you are describing.

When you put two windows together (i.e. mull two units) it is done with a mullion strip or clip that attaches into the exterior accessory groove of the outside and inside.

If you are creating the rough opening, you can just give whatever manufacturer you are ordering from that measurement and they will create the twin unit that will fit that opening.

It will be factory mulled which is preferable most times anyway.

    Bookmark   October 10, 2010 at 11:16PM
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Hi windowsonwashington,

Thank you so much for that clarification about the "factory mulled" windows. And for the "twin double hung" phrase!

That's very helpful to know that the manufacturer will create the twin unit to fit the opening measurement. Another one of those facts I didn't know that I didn't know. :-)

    Bookmark   October 11, 2010 at 11:38AM
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