Velux windows are always placed in the roof of an extension and are an excellent way to add light and a feeling of space to the room. To maximise their potential the windows should be installed in the centre of the roof – rather than above a door or opposite a window. That’s because it is the centre of the new extension that will be darkest and require the most daylight. In total the windows installed in the roof of your new home extension should be equivalent to around 15 to 20 per cent of the floor space. Meanwhile, it’s also possible to buy special windows for conservation area to ensure your house doesn’t look out of place and will pass English Heritage guidelines.