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Using 2 windows in each opening

breadysmith | Posted in Green Building Techniques on

I have a thought that I would like to get forum experts to chime in on. I’ve tried searching to find an answer and google is never kind to my efforts.

My thought is, is it possible to use two windows in each opening. The concept being that buying two less expensive…in my case I’d still go with fiberglass for expansion concerns. So two windows in the same opening. Ideally sliders in my case so the sashes line up well and there is no impact in the visibility through the window with sashes not lining up and getting in the way.

Also, if new construction you could easily run power to each window and I envision running motorized double cell honeycomb cellular shades with side seals and black out material.

So window one a traditional new construction window with the attachment flange. The second one a replacement window set about 2 inches or so in from the outside window. Allowing enough room to essentially sandwich the cellular shade between the window assembly.

I realize the wall would need to be at least a 2X6 or ideally a double stud wall, which would be doable.

I envision this with the two windows of a decent quality, coupled with the sealed airspace and the cellular shade providing a pretty effective r-value for a window opening.

The added benefit being sound reduction due to the airspace and even the possibility of laminated glass or varying the thicknesses of the glass units to assist with noise.

Then the benefit of having a VERY effective blackout solution with the cellular shades and the side seals…which would be essentially not visible being obscured by the side of the window sashes.

I hope all of this make sense. I am hoping the expertise of the forum will assist me in catching any potential issue or problems that could arise from this type of configuration.

Also, I would line the 2 inch gap between the two windows with something waterproof like a PVC in the event that condensation does occur between the windows.

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  1. GBA Editor
    Martin Holladay | | #1

    It might be easier if you just bought Pella windows. Pella offers triple-glazed windows with "between-the-glass" shades.

    Here are two links:

    Pella Between-the-Glass Blinds

    Windows: Between-the-Glass Options

  2. Yupster | | #2

    Cleaning the second window might be a problem. Also operability of the windows might be difficult. Seems like a lot of heat might get trapped in the space between the two windows, might be hard on the window seals. Never done it though. You are basically asking if you can attach a double glazed storm window. Maybe try googling that, you might get better results.

  3. this_page_left_blank | | #3

    You can also look at "Indow", which looks to be halfway between your double window idea and the Pella option. The risk/cost to potential reward ratio of your double window idea doesn't look that promising to me.

  4. MarkM3 | | #4

    Very creative idea - I've had the same thought. I'd bet you'd spend less with two fiberglass (or composite, like Andersen 100 series) windows versus the Pella. Heat build up might be my only concern. But I cannot emphasize enough how prototyping my hair-brained ideas has served me over the years... it is a risk to roll out this scheme across the entire house. What if you committed to walls of adequate thickness, and did the traditional window in the traditional location, and only did a double window as a test case in a single location - maybe on the south side of the house? You could stick a thermometer in between and monitor how it behaves - and if you delay sheetrock work, maybe get enough data to move forward with other windows? It would be a logistical challenge, holding off ordering and installing additional windows - you may or may not have a timeline that could support that. I guess the heat buildup concern would be less of an issue with operating windows versus picture windows... you could always leave the interior one open a bit if it did get inappropriately toasty in there. Just thinking out loud... Best of luck, Mark

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