Toni-
My Library finished a project to mitigate light and heat using window films and shades a few years ago. I can share a few thoughts about the process and materials.
We collected recommendations from a number of sources, but leaned heavily on a National Park Service Conservo-gram on the subject of UV-filtering films https://www.nps.gov/museum/publications/conserveogram/03-10.pdf. It probably needs to be updated.
After identifying some products we wanted to look at, we contacted 2 local providers and asked them to come view the space and bring samples. We used these to make final decisions.
We ended up installing 2 varieties of SunScape film https://madico.com/sunscape to block both visible light and UV. One of the films blocked more visible light than the other. We have been happy with the product and it has significantly reduced heat, UV and glare. In one room, in addition to the window film, we also installed shades that could block light completely when down. This was a Draper product. They also sell shades that only filter light, which might be more appropriate for your space.
A few things to bear in mind (and that I wish I knew beforehand):
1) The film manufacture's definition of UV may be different from the one we (ie conservators) use. Be sure to ask them about it.
2) As I understand, there is no film that will block all UV as well as a significant amount of visible light. If a film blocks all UV (or close), it doesn't block much visible light. The film we chose blocked a lot of UV, but not all, as well as some visible light.
3) These films don't last forever. I think after about 10 years, you need to start thinking about replacement.
Good luck on your project. I will be interested in hearing what you decide on.
Best,
Susie Cobbledick
Book Conservator
Missouri Botanical Garden Library