A hot air balloon carrying a council planning officer with a heat camera has ascended over Gloucester.
Meyrick Brentnall is using the torch-like device to check how well the city's buildings are insulated.
The airborne exercise marks the launch this week of the council's climate change strategy.
Its aims include improving the energy performance of new buildings, promoting greater use of public transport and expanding recycling services.
Mr Brentnall took flight over the city with the heat camera on Friday morning.
"We're looking down on houses, offices and factories and will take the information back to the office," he said.
"It's a way of raising awareness on how important insulation is and encouraging people to insulate their buildings."