We attended a callout to a property in Berkshire because the homeowner was worried about misted double glazing. The majority of double-glazing frames will expand in the cooler and warmer months; over time, this exposure to temperatures can loosen the seals. 
We quickly established the reason for the misted up double-glazing and replaced the sealed unit. 
If you are worried about misty UPVC windows, we can help you put things right quickly.