A simple way to check for air leaks in window frames is by using a candle. When the flame is brought near the window frame, any flickering, tilting, or extinguishing of the flame can signal the presence of an air leak. These leaks can cause heat to escape from a home, leading to higher heating costs and a colder indoor environment. The method involves holding a steady, medium-sized flame about two to three centimeters away from the window frame and slowly moving it along areas that are more prone to leaks, such as the corners, edges, window sills, and around the handle. This technique has been used by carpenters and builders for many years before modern tools like thermal cameras became available. It works based on the principle that even the slightest air movement can affect a flame, even if the movement is too subtle to feel on the skin. Testing during a cool or windy day can make these leaks more visible, as the temperature difference between the inside and outside of the home becomes more pronounced. A flame that remains steady and straight typically indicates that the window is well-sealed and airtight. However, if the flame flickers or goes out, it suggests there is an air leak in that area. These small leaks, though often unnoticed, can add up and significantly contribute to heat loss during colder months. They may also cause drafts, increase the workload on heating systems, and raise energy bills. This simple and cost-free method allows homeowners to quickly identify air leaks in their windows before exploring more expensive solutions. It’s a practical way to improve energy efficiency and comfort in the home without the need for specialized equipment.