You might be ventilating your rooms more than ever during cold winter days, but if you’re still seeing condensation forming on your window panes, check if there’s a gap somewhere. It’s easily done. Light a candle or a tea light and hold it close under the window frame. If you see the flame flickering more than before, when it was further away from the window frame, then you may well have a leak. You can also light an incense stick to carry out this easy test, according to a German consumer advice centre. Most likely, you’ll need to replace the porous rubber seals, say experts. Or readjust the …