Secondary double glazing for patio doors?
 

Hi,

I have a largish patio door (approx 270cm x 207cm) which already has
aluminum double-glazing (two equal size panels, one fixed one sliding). I
want to improve the sound insulation (noisy road nearby) and I am
considering adding secondary glazing for this.

I would like to maintain the same design (two doors) so each panel will be
approx 200cm x 130cm. Is this possible - these would be large sheets of
glass? Could I use plastic sheeting instead? Would it have a similar sound
deadening effect as glass?

Finally, does anyone make such large aluminium secondary units? I guess it
would have to be aluminium even if I used plastic glazing.

Thanks for any info,

John Smith.