When you had that skylight or roof window installed, you may have had the idea of stargazing from the comfort of your bed. You also wished to get some sun without having to take a walk. It held pretty well in the rainy season but soon as winter came you got an annoying leak that made you regret the installation. This is a common problem today especially with the influx of so called skylight installation specialists and low quality component. Unlike in rainy season, winter may allow for a build up of ice on and around your skylight. This may lead to condensation as a result of temperature differences between the inside and the exterior. One cause may be that the skylight window is not properly insulated and you may consider getting a replacement window of better quality. A second cause may have to do with the skylight flashing which may just need to be redone by an expert skylight installer. It may need a lot of work that may result in the spread of debris on the space below. The lesson here is to always get a professional to do your skylight installation to avoid so much hassle in future.