Double glazing has two layers of glass with a gap of around 20 mm between them (4-20-4) with argon gas, white spacer bar as standard, low E soft coated. Triple glazing has three layers of glass with 36 mm thickness (4-12-4-12-4) with argon gas, spacer bars as standard, low E soft coated. Triple glazing will provide significantly more noise and heat insulation than double glazing. Both are A-rated.