We have just had installed the UK's most advanced windows at A+33. So what do we think? Well, they are certainly very, very quiet. It's not been cold enough to see if we can turn the heating down yet, but if they hold all noise out then it must do the same for cold/heat. They close very smoothly, and tight. A. Massive improvement on look from our old windows and doors. A smashing company, nice people and not your usual double glazing 'sales' tactics.