I am waiting for my new car to be delivered and I noticed on the accessory list that I will get 5mm glass in the side windows.

Why is that put as an accessory?
What is the normal glass thickness?
What's normal in a Volvo (if different from other brands)?

Being in Europe may be part of the reasoning for your curiosity.

I just went out side and checked my side windows for comparison and mine are 4mm thick.

Some of the possible reasons may be due to the safety laws or codes of any particular country, and the ticket you have may take this into account by specifying which glass is required for your country.

Most side glass is tempered, not laminated as the windshield is. I did notice though that in Europe it is not uncommon for certain vehicles to have side laminated glass as well, which has been stated to be due to helping to prevent theft in Europe (although it apparently is not a common practice in the US). The laminating proceedure might be another reason, slightly adding to the glass thickness.

My guess is probably that is it due to safety regulation for specific countries. In Europe it may be a necessary line since they can delivery to many countries outside of where the plant is located, and every country in Europe might have different requirements. In the US it may not be a standard line on the ticket since we have some Volvo plants here, and they largely supply the US/Canada only, and therefore may not have various safety regulations to deal with.

Allright.. thankyou
(can't believe you actually went out to check :) )

I don't think it's because of regulations.
So I guess the extra thickness is because I get laminated side windows thrown in or just because the isolate from outside noise.

I must admit that I didn't pick all the equipment myself. It was part of a special package. :)

The stardard window thickness here in the US seems to be 4mm, I would guess, but that is Pilkington Glass. Volvo uses glass from other places too, and in Europe they may use someone else, which provide 5mm standard.

It's hard to say I guess. I would only expect that Volvo chooses what they find to be best for safety and you may be getting better glass than normal, or it's simply a new upgrade option being offered, although I really cant say I have ever heard of a car manufacturer offering a glass upgrade...maybe Volvo does.