People living in period properties are being told they can dramatically reduce their energy bills, simply by closing their curtains or shutters at dusk.
Edinburgh researchers claim it could be as effective as fitting double glazing.
The Edinburgh World Heritage Trust has been using thermal imaging cameras to show residents of the capital's old and new towns how best to cut their bills.
The project has demonstrated a traditional, decidedly low-tech approach can be highly effective.
Windows with the shutters and curtains closed show up in the images in a deep blue colour, demonstrating little heat is escaping.
Windows with the shutters and curtains open burn bright in oranges and reds, showing that much more heat and money is being lost.
The team behind the project said other traditional techniques were valuable too and anyone living in a period property should also not overlook the importance of draught excluders.
Chiara Ronchini, energy efficiency officer for Edinburgh World Heritage, said: "We know that improving energy efficiency in historic buildings is very important if we're to reduce carbon emissions and alleviate fuel poverty.
"There are issues, of course, with historic buildings but they are so well designed that they just need a little push to make sure that they are performing as well as the most modern buildings.
"The thermal imaging exercise really proved that very simple measures, like closing shutters at night or using full length curtains, can have a dramatic effect and make a dramatic improvement on the amount of heat being lost through the windows."
The project is funded by the Climate Challenge Fund.