Many modern uPVC and tilt-and-turn windows feature a "winter mode" that allows for manual adjustment of the locking cams, increasing pressure against the rubber seals to eliminate drafts and improve energy efficiency. This adjustment involves using a tool like an Allen key to turn the cams to a tighter setting, reducing heat loss by up to a third. For a demonstration of this technique, watch this YouTube video . PUT YOUR WINDOWS INTO 'WINTER MODE'