How Do You Protect Museum Collections and Historic Interiors From Sunlight?

Window film can help protect museum collections and historic interiors by blocking ultraviolet light and reducing visible light and solar heat, and a clear or light film can do it without changing how the building looks. Blocking ultraviolet alone cannot prevent fading, because visible light also fades many sensitive colors. That is why conservators usually ask for a film that blocks ultraviolet and also reduces some visible light, and why film works alongside blinds, shades and careful placement of objects, not instead of them.

Key points

• The Canadian Conservation Institute notes that for light-sensitive colors, ultraviolet usually causes less than half of the fading and often only a tenth. The rest comes from visible light.
• Conservation guidance sets limits for both. The National Park Service standard is ultraviolet below 50 microwatts per lumen. The traditional visible light rules the Canadian Conservation Institute describes are about 50 lux for textiles, works on paper and photographs and 150 lux for oil paintings and furniture.
• Solar Gard rates its architectural films at more than 99 percent ultraviolet blocked, measured from 300 to 380 nanometers. Conservators count ultraviolet up to 400 nanometers, so a meter reading on a sample is worth having.
• On 1/4 inch clear glass, Solar Gard rates fade reduction at 37 percent for clear Sterling 70 and 88 percent for dark Panorama Slate 10. All three films in our comparison block more than 99 percent of ultraviolet; the difference comes from visible light.
• For museums and historic buildings, the film we typically see approved lets through about 70 percent of visible light, because most of these clients do not want the building’s appearance to change.
• Our projects include clear UV film on 331 panels at Fabyan Villa Museum, Sterling 70 in the main exhibit at the National Indo-American Museum and Slate 10 on 72 skylight panels at Richard Gray Gallery.

Does UV window film stop fading?

No. It slows one cause of fading. The Canadian Conservation Institute separates the damage: ultraviolet mainly yellows, chalks and weakens materials, while visible light mainly fades colors. For light-sensitive colors, it says ultraviolet usually contributes less than half of the fading and often only a tenth. Its conclusion is that the only way to reduce fading is to reduce light exposure.

Sunlight through a window also heats what it lands on. The Institute notes that direct sunlight can warm surfaces 40 degrees Celsius above the room, which speeds up the chemical decay of many materials. Window film helps with all three parts of sunlight, ultraviolet, visible light and heat, but by different amounts depending on the film.

What do conservators usually ask for?

Targets for both ultraviolet and visible light, set by how sensitive the objects are. The figures most often cited come from two sources:

• Ultraviolet: the National Park Service standard is below 50 microwatts per lumen, and preferably lower. The Canadian Conservation Institute gives a traditional limit of 75 microwatts per lumen.
• Visible light: the traditional rules the Canadian Conservation Institute describes are about 50 lux for textiles, works on paper and photographs, 150 lux for oil and acrylic paintings and furniture, and 300 lux for stone and metal.
• Total exposure: damage depends on light level multiplied by time, so conservators also think about how many hours a year an object is lit.

A window film alone will not bring a sunny gallery to 50 lux. What it can do is take ultraviolet off the table at the glass, cut down the daylight and heat coming in, and leave the remaining control to shades, blinds, display cases and where objects are placed. In our experience, the conservator sets the targets and the film is chosen to help meet them.

What does “blocks more than 99 percent of UV” mean?

It means more than 99 percent of ultraviolet in the range the film industry measures. Solar Gard’s data sheets rate ultraviolet blocked from 300 to 380 nanometers. The Canadian Conservation Institute notes that convention places the boundary between ultraviolet and visible light at 400 nanometers, and that the window industry often rates glazing to 380.

The National Park Service makes the same point for museums in its guidance on choosing UV-filtering window films: most solar films filter only to about 380 nanometers, and performance can vary from batch to batch, so it recommends testing a sample with a meter before installation. For a museum or a room holding sensitive objects, ask for a sample on the actual glass and let the conservator take a reading.

Clear film or darker film?

It depends on how much visible light the space can give up. All three Solar Gard films below block more than 99 percent of ultraviolet. What separates them is how much visible light they pass, and Solar Gard’s fade reduction rating follows the visible light:

Solar Gard ratings on 1/4 inch single clear glass. Fade reduction is calculated against the same glass without film.

For museums and historic buildings, the film we typically see approved is one that lets through about 70 percent of visible light: it blocks ultraviolet, takes some of the light and heat off the room and keeps the windows looking much as they did. The National Park Service cautions that metallic or very dark films are not suitable for historic buildings. A dark film like Slate 10 makes sense where the light itself is the problem and appearance matters less, such as a gallery skylight.

Can film go on historic glass without changing how the building looks?

Yes, with a clear film, installed on the room side of the existing glass. At the Fabyan Villa Museum in Geneva, a house remodeled by Frank Lloyd Wright in 1907, we installed clear Solar Gard UV film on 331 window panels across nine rooms, each small pane cut and fitted individually. The windows look as they did from inside and out. See the Fabyan Villa case study.

Historic glass needs the same check as any glass, and sometimes more. Solar Gard’s film to glass guide lists which films are approved on which glass, and its glass breakage and seal coverage is not available on damaged, chipped, cracked or scratched glass or in buildings with a history of glass breakage. We look at historic glass closely before recommending a film. We explain the film to glass check in Will Window Film Crack Your Glass?

Film can generally be removed and replaced without replacing the historic glass, provided the glass is in suitable condition and the right removal method is used for it. We explain the process in How Do You Replace Old or Failing Window Film?

What about galleries, skylights and display areas?

Overhead glass lets in the most light, and it is where a darker film often earns its place. At Richard Gray Gallery in Chicago in 2021, we installed Panorama Slate 10 on 72 skylight panels. Skylights need their own check: Solar Gard’s glass breakage and seal coverage does not extend to interior film on skylight glass, so the film and the side it goes on are settled before the order.

Display areas near windows can be handled with a clear film instead. At the Chicago Bears’ Halas Hall in Lake Forest, we installed Panorama Hilite 70 on the glass near the trophy cases and memorabilia displays in 2017. At the National Indo-American Museum in Lombard in 2021, we installed Sterling 70 on 11 panels in the main exhibit. See the Halas Hall case study.

How long does UV window film last?

In our experience, most interior films last around 20 years, depending on the product and conditions. The National Park Service’s guidance, written in 2004, gives UV-filtering films an effective life of 8 to 15 years. For a collection, the safer approach is not to rely on age alone: have the ultraviolet at the window checked with a meter from time to time, and replace the film when the readings or its condition call for it.

Which museums, libraries and historic buildings have we worked in?

UV protection is built into virtually all the architectural window films we install. Many of these projects therefore provided UV reduction alongside their primary purpose, whether privacy, solar control or decoration.

Museums, galleries and collections

• Fabyan Villa Museum, Geneva: clear Solar Gard UV film on 331 panels across nine rooms, 2024.
• Chicago History Museum: UV-blocking window film for comfort and protection, 2021.
• National Indo-American Museum, Lombard: Sterling 70 in the main exhibit, 2021.
• Richard Gray Gallery, Chicago: Panorama Slate 10 on skylight panels, 2021.
• Chicago Bears, Halas Hall, Lake Forest: Panorama Hilite 70 near the trophy cases and memorabilia displays, 2017.

Libraries

• Itasca Community Library: exterior Sentinel Plus DX 15 in youth services and offices, 2026.
• White Oak Library District: Slate 20 in a study room, 2026.
• Lisle Library District: Sterling 70 on 16 panels, 2025.
• Barrington Area Library: window film on doors and sidelites in 2025, and decorative film in 2022.
• Holy Angels Catholic School: Truvue 5 in the library, 2025.
• College of DuPage: frosted film in in the library, 2023.
• Crystal Lake Public Library: decorative film, 2021.
• McHenry County College: film in the library office, 2021.
• Ella Johnson Memorial Library, Hampshire: Sterling 60 on corner windows and Slate 20 on entry transoms, 2020.
• Thomas Ford Memorial Library, Western Springs: decorative gradient and frosted film on 24 panels, 2019.

Historic theaters

• Lyric Opera of Chicago: film on the entrance doors in 2024 and at the stage entrance in 2026.
• The Chicago Theatre: replacement film, 2024.

Not all of these were about protecting collections. Libraries and theaters often want comfort, glare control or privacy as much as protection, and the film is chosen for the job each space has to do.

What is the next step?

Start with the conservator or collections manager, if you have one, and the targets they work to. Then have the glass looked at in place: we identify the glass, check the film against the manufacturer’s guidance and put samples on your windows so you can see the change before deciding, and a meter reading can be taken on the sample. We do not subcontract installation; our own crews do the work. See our solar control window film service and the performance terms guide, or request a free assessment.