The win­dow sticker that cuts your elec­tric­ity bill by 10%

Sunday Times (Sri Lanka) - - INTERNATIONAL - By Harry Pet­tit © Daily Mail, Lon­don

A heat-block­ing film that you can stick on your win­dows could re­place the hum­ble air con­di­tioner.

Sci­en­tists say the see through ma­te­rial keeps out 70 per cent of the sun's rays and au­to­mat­i­cally gets darker as tem­per­a­tures rise to re­ject more heat on hot­ter days.

The team claims that if every ex­te­rior- fac­ing win­dow on your house were cov­ered in this film, the build­ing's air con­di­tion­ing costs could drop by 10 per cent.

In the US, it's es­ti­mated that air con­di­tion­ers use around six per cent of all elec­tric­ity.

This costs $29 bil­lion (£22 bil­lion) an­nu­ally - an ex­pense that's ex­pected to grow as ther­mostats climb with global warm­ing.

Re­searchers at the Mas­sachusetts In­sti­tute of Tech­nol­ogy (MIT) de­vel­oped the heat-re­flect­ing film.

It shrinks and be­comes opaque when ex­posed to tem­per­a­tures of 32C (89F) or higher.

Be­low 32C the film is fully trans­par­ent and does not re­flect heat.

It is hoped that the ma­te­rial can be pro­duced for homes and busi­nesses to use on win­dows dur­ing sum­mer month heat­waves.

In a trial, engi­neers ap­plied a so­lu­tion of the heat-shield­ing sub­stance be­tween two sheets of 12-by-12-inch glass to cre­ate a film-coated win­dow.

They shone light onto the win­dow to mimic in­com­ing sun­light.

The film turned frosty in re­sponse to the heat, re­flect­ing 70 per cent of the heat pro­duced by the lamp.

The poly­mer ma­te­rial is ther­mochromic and will tem­po­rar­ily change phase or color in re­sponse to heat.

MIT Pro­fes­sor Ni­cholas Fang says the ma­te­rial pro­vides an af­ford­able and en­ergy-ef­fi­cient al­ter­na­tive to ex­ist­ing smart win­dow tech­nolo­gies.

Prof Fang said: 'We thought there might be room for new op­ti­cal ma­te­ri­als and coat­ings to pro­vide bet­ter smart win­dow op­tions.

'Smart win­dows on the mar­ket cur­rently are ei­ther not very ef­fi­cient in re­ject­ing heat from the sun, or they may need more power to drive them, so you would be pay­ing to ba­si­cally turn win­dows opaque.

'Meet­ing this chal­lenge is crit­i­cal for a met­ro­pol­i­tan ar­eas like Hong Kong, where they are un­der a strict dead­line for en­ergy sav­ings.'

The re­search was pub­lished in the jour­nal Joule.

Sci­en­tists say that the see through ma­te­rial keeps out 70 per­cent of the sun ray's and au­to­mat­i­cally gets darker as tem­per­a­tures rise to re­ject more heat on hot­ter days

A see-through film that you can stick on your win­dows blocks 70 per cent of the sun's heat

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