Low-e window film

Available from: specialist solar film companies Installation: by professionals

Low-e film (low-emissivity film) is a thin polyester film with a micro-thin, transparent metal coating. It is stuck directly to the inside of single-glazed windows to reflect radiant heat, either from outside or inside, reducing the amount of energy you need to heat or cool your home.

BRANZ research shows low-e window film can reduce heat loss through single glazing by up to 25%. In comparison, double glazing, secondary glazing and DIY window insulation kits can reduce heat loss through glazing by about 60%.

Low-e window film on single glazed windows works best in houses that rarely experience condensation on windows, according to the BRANZ research. Like condensation on a bathroom mirror, the condensation on the low-e film means the glass surface is no longer reflective and if condensation is present, the low-e surface provides very little benefit over normal glass. Once the condensation has dried up, the performance of low-e window film is restored.

Tackling damp at source and good ventilation and heating practices may help to reduce the amount of condensation that forms when low-e window film is fitted.