This is a special double glazing of 10mm with a minimal spacer of 4mm.
Float 3mm / 4mm spacer + argon / float 3mm low-e. U-value of 2.3
This version of double glazing is intended for restoration of very old " single glass " windows who doesn’t have enough space for normal double glazing and therefore require an alternative.
This double glazing is often combined with one of our many restauration glasses
A balance is created between the restoration of the authentic view and the better insulation to reduce energy waste.