Windows are usually the weakest point in a home's thermal envelope. Solar control film reduces the amount of heat entering through the glass, which eases the load on air conditioning during the hottest part of the year and helps keep temperatures steadier from room to room. It also filters UV and cuts glare, so the comfort gain is not only about temperature. For homeowners weighing up options, film is applied to existing glazing and is worth comparing against full window replacement before committing to either. Which film suits your home depends on the glazing you already have, so identify that first — a dealer can advise on what is appropriate for single, double or already-coated units.