Wondering about the reliability of your home’s original windows? On a windy day, pull up your blinds and hold a candle near the edges of each of your windows. If the candle dances when the wind blows, you may have a leaky seal. This means that cold air is not only coming in, but your expensive heat is going out, too. To address this issue, first go outside: Look for gaps in the wood surrounding the frame and use caulk to seal them up. Then, head inside: There’s a wide range of weather stripping products you can buy for windows, including metal v-channels, reinforced felt, and expandable foam strips—these materials are nailed or self-adhered along the inside edges of the window and along the bottom of the sill to produce a tight, wind-proof seal. Each of these products will compress when you close the window, so the window can still be locked. Talk to your local hardware store expert about what option is best for your home’s vinyl or wood windows. With the right materials in hand, a project like this can be a quick, one-afternoon DIY.