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 Safely blacking out double-paned windows?

Niku Radan's profile image
Niku Radan posted 07-28-2026 10:09 AM

Hi everybody,

I work for a museum-adjacent nonprofit and am trying to sort out an operations issue. We're planning to host an exhibit which will need to take place in near-complete darkness but the space we've designated for it has approx 15 ft tall double paned windows lining the walls. 

We planned to use blackout tint to block the light but blackout tint is apparently extremely unsafe with double paned windows, as it absorbs UV rays and can break the double pane seal/ heat up the glass to the point of cracking. Our next most apparent option is blinds, which may also be tedious only because of the size of the windows. I'm writing this here because I feel other professionals may have dealt with similar issues-- is there any other way we can block light without damaging or heating up the glass?

Bruce MacLeish's profile image
Bruce MacLeish posted 07-28-2026 05:02 PM
Hello Niku,
During several decades working in museums, I used various methods for reducing natural light coming through windows, but only occasionally had to find methods for eliminating natural light entirely.  There are many considerations involved in using any sort of adhesive tinted film -- if that is what you are thinking of -- and I have seen vendors' lists of ten to fifteen conditions that would void a window film installation. The heating component of natural light, not ultraviolet, could create high temperatures in the window glass itself -- possible enough to cause the window glass to crack or shatter. A very dark tint is much more apt to create problems than a lighter one.
When blackout conditions were required, opaque shades worked well. If absolute darkness was required, light baffles along the edges of the shade might be needed, which can make installation a bit complex. Rigid panels can be used, employing plywood or other materials, and potentially requiring baffles as well, allowing heat to escape, rather than build up next to the window glass. Depending upon where your museum is located, heat buildup in such situations can be considerable, and areas of intense summer heat are becoming more widespread, of course. 
I would suggest working with a vendor with experience working with museums, if possible. Insist on a warranty for materials and installation in any case.
Best,
Bruce
A. B. MacLeish
Curator Emeritus
Newport Restoration Foundation
85 Lake Street
Cooperstown, NY 13326
abmacleish@verizon.net
(C) 401-265-8607
Melissa Tyrone's profile image
Melissa Tyrone posted 07-29-2026 09:20 AM

Hi Niku, 

We confronted this issue with windows in our exhibit hall. Our solution was to build boxes to cover the windows and integrate them into the exhibit. From the outside, the windows are simply dark--but we did not add anything extra film or covering to them. From the inside, they look like exhibit panels. They were not expensive to fabricate and install. 

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Matthew Isble's profile image
Matthew Isble I'm Connected posted 07-29-2026 03:12 PM

We have cracked windows, so you're right to think about this ahead of time. We used Melissa's (below) technique of creating boxes to instead into the windows. the windows faced the west and it gets hot her win Sacramento. Two of the 10 windows cracked, luckily they weren't the curved panes.

On the east side we created a false wall for the floor to ceiling windows, but this time we left a 1" gap at the top (with a light baffle) to let out some of the trapped heat. It may be working because it's the east side and gets far fewer light hours than our west facing windows, or maybe the 1" gap is the secret sauce. I can't say for sure. But you do want to think about direction and light hours.

What HAS worked on every window is SolveX window film. It's perforated at 70/30. It's made a big difference. They aren't blacked out, but there is 70% less light. I hope that helps?

Good Luck,

Matt

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