I was reading a post in a window fitters’ group where an installer posted a picture of a large insulated glazed unit with the question “how much does that glazed unit weigh?’
Maybe it wasn’t a question but rather an opportunity to boast to his mates what a large, glazed unit he was handling? But in my experience working in sales/estimation for Polish window manufacturers, “industry professionals” would ask me all the time to confirm the weight of windows and glazed units.
But there is a fast and effective rule of thumb!!
1m2 of glass (1mm thick) weighs approximately 2.5kg
So, if we consider the glazed unit in the picture above. The largest one on the diagonal timber stands in the back of the container.
The spec was:
Dimensions = 2760mm x 3003mm
IGU spec:
Step 1 = calculate glazed unit surface area = 2.76 m x 3.003 m = 8.29 m2
Step 2 = multiply glazed unit surface area by 2.5 kg = 8.29 m2 x 2.5kg = 20.72 kg
Step 3 = multiply this figure by the total glass thickness = 20.72 kg x 16 mm = 331.5 kg
How do you find your glass thickness
- From the specification on your glass and window order documents
- On the production sticker if it’s still attached to the glass
- Or eventually it’s often printed on the glass spacer
Laminated safety glass:
Laminated safety glass is often identified as 33.1 / 44.2 / 44.4 etc.
The two numbers before the full stop refer to the thicknesses of the two layers of glass
The single number after the full stop refer to the quantity of PVB foil interlayers (1 standard foil interlayer has 0.38mm)
33.1 = 3mm glass / 1 layer of foil / 3mm glass
total thickness = 6.38mm
consider 6mm glass thickness for weight.
44.2 = 4mm glass / 2 layers of foil / 4mm glass
total thickness = 8.76mm
consider 8mm thickness for weight
So let’s look at another example with triple glazing and inner laminated safety glass. I have added some other common glass markings you might find.
For example, lets consider 850mm x 1650mm
Step 1 = calculate glazed unit surface area = 0.85 m x 1.65 m = 1.4 m2
Step 2 = multiply glazed unit surface area by 2.5 kg = 1.4 m2 x 2.5kg = 3,5 kg
Step 3 = multiply this figure by the total glass thickness = 3.5 kg x 20 mm = 70.1 kg
Using this rule of thumb, you can make a fair estimation of your IGU weight.