Originally posted by gmcd
Window films should be applied to the exterior glass surface of double pane windows. By putting them on the inside surface you can overheat your glass as the tint absorbs solar load and heats the inner pane of glass and the airspace. It's OK to put the peel'n'stick tint films on the inside surface of single pane glass because you don't have the air space to deal with. Yes, they need to be washed carefully when the tint film is on the exterior, no different than when the film is on the interior pane anyway.
Solar control starts when the architect puts pencil to paper- exterior shades, glass selections, etc. Dollars spent on better glass and solar control= smaller HVAC system and lower on-going energy costs.