A: That will depend on whether you have plexiglas “domed” skylights, or “flat” glass skylights. Plexiglas has plasticizers in it that can attack the film adhesive; discoloring the adhesive and requiring removal. Since the removal process itself would ruin the plexiglas, it is a classic “Catch 22″ situation. More importantly, the film won’t conform to a “domed” shape without severe wrinkling, or installation in multiple pieces – neither of which is pleasant to look through. Many people opt to have a piece of glass installed under the skylight itself, and then install film on the glass.
Glass skylights are flat and therefore the film can be installed directly to them. A word of caution, however. Most glass skylights are insulated “double-pane” glass; many with a “low-e” coating, and as such, there are films that you definitely do not want to install on them without risking glass breakage or seal failure. You should also know that no window film manufacturer (to our knowledge) will warranty a skylight installation, due to the fact that they face directly into the sun. That having been said, we install film on skylights fairly often, and it lasts for a substantial period of time.
If you must access the skylights from the outside, make sure you insist on the use of “outside weatherable” films – films that are specifically manufacturered and warrantied for exterior application – otherwise, the film will not last long at all. Our SolarGard® “Sentinel™” series films are backed by a two-year warranty on non-vertical glass, and are safe to install on any glass skylight window unit.