I've just had new Rehau double glazed units fitted and noticed that the frames have what is called 'knock-ons' (?) at the top, making more plastic visible and making the window size smaller - not by anything much but obviously with UPVC double glazing the less plastic and more glass the better.
Why would these be needed when the surveyor measured brick to brick, I thought new units should be made to measure as one unit?
Any good or bad reasons appreciated - do they have an impact on the performance of the double glazing?
Why would these be needed when the surveyor measured brick to brick, I thought new units should be made to measure as one unit?
Any good or bad reasons appreciated - do they have an impact on the performance of the double glazing?