Spy-in-the-sky cameras are being used to identify householders who are wasting the most energy and to shame them into turning the central heating down.

Thermal images of homes have been taken by a light aircraft fitted with military spy technology to record the heat escaping from people’s houses.

Maps identifying individual homes have now been placed on the internet to encourage occupiers to reduce their wastage and carbon emissions by fitting insulation and turning the thermostat down.

Haringey Council, in London, has become the first authority in England to place house-by-house thermal maps on the web, after the example of Aberdeen in Scotland.

Making the information available to the public is intended to raise awareness of how much energy is being used needlessly, putting up bills and contributing to global warming.

It is hoped that homeowners with high wastage levels will be shamed into improving the property’s insulation.

Other authorities have shown interest in the spy technology, including Chester-le-Street District Council, which carried out a survey but has yet to put data on the web, and Norwich, which is considering the idea. It is seen as part of the armoury against global warming, which scientists are convinced is worsening because of man-made carbon emissions.

Haringey’s mapping took place on a winter’s night when households were likely to have the heating turned up high.

An aircraft, fitted with a military-style thermal imager, flew over the borough 17 times to take pictures of almost every house in the area.

Footage of heat loss was converted into stills, then laid over a map of the area, before each house was given colour-coded ratings.

Homes that were losing the most heat were represented as bright red on the map. The least wasteful households were shown in deep blue. Shades of paler blues and reds were used to show grades of heat loss.

Officials from the authority shrugged off suggestions of a Big Brother-style invasion of privacy by prying on people’s properties and then publishing the information.

They said that they hoped to use the maps to pinpoint the homes where grants should be offered and to identify empty properties that could be used to lessen the housing shortage.

Isidoros Diakides, a councillor, said: “This single study will play a key role in helping us address three of the biggest issues currently facing Haringey — climate change, fuel poverty and housing waiting lists.

Robert Wilkes, the owner of hotmapping.co.uk, which conducted the thermal surveys, said: “I think it is less intrusive than Google Earth quite honestly.

“It’s not a photograph; it’s merely a measure of heat loss. I think everybody should find it very useful – particularly businesses, schools and hospitals.”

Haringey’s thermal survey took place in 2000, but fresh spy camera flights took place in March. The heat maps will be updated when the new data have been processed.

Almost 60 per cent of a household’s heat is lost through uninsulated walls and lofts, according to the Energy Saving Trust (EST), costing the average home up to £380 each year.

Insulation is estimated to reduce each home’s carbon emissions by about two tonnes annually.

More than half of the UK’s carbon dioxide emissions come from the domestic sector, taking into account both homes and transport.

Philip Sellwood, chief executive of the EST, welcomed the initiative to reveal the location of wasteful properties.

He said: “By and large we think it’s a good thing, as long as they are following it up with information and advice.

“If they are just doing it to highlight a problem without offering a solution, that’s no good to anyone.”

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