I'm putting central heating into a flat which previously had storage heaters. I found evidence of poor ventilation, with black mould build-up most pronounced in the bedrooms. I suspect this is due to a lack of trickle vents in the double glazing. The floor is concrete and the walls are cavity (without insulation). In addition to trickle vents, I'm being advised to install air bricks behind the radiators, under the windows. Everyone I've asked has never heard of air bricks behind rads. Does anyone know if this is a good idea or not?