The benefits of e-glass or double-glazing are neutralised when windows are not sealed correctly. On visual inspection, most buildings have properly sealed windows, however on closer inspection and using blower door, tracer gas and thermal imaging technologies, it is common that windows and doors are identified as key sources of air leakage.
Light fittings are also a major cause of air leakage. Lighting contractors are often one of the last contractors to work on a building site. Their focus is on electrical safety, quality of light and aesthetics of the final install. They do not consider the impact they make when they puncture the internal air barrier to install their lights.