During the heatwave last summer, our top-floor apartment felt like an oven because of the massive skylights in the roof. Air conditioning units are expensive to run, so we looked for passive heat reduction methods first. Ordering reflective roof-light window film via https://www.tintfit.com/shop/ was easily the best investment we made for the flat. It reflects a huge percentage of solar heat before it even enters the room, meaning the apartment stays at a manageable temperature even on thirty-degree days.