This question requires consideration of several factors to be able to determine the correct answer.
The first point to consider is if you are installing the second window in your own property (inside your lot boundary). I would assume you are, so there are only a couple of other small factors to consider.
As you say, the external appearance of the lot will remain unchanged after the installation. This is good, as if it was to change, then you would need to seek the Owners Corporations consent prior to proceeding. See Section 5.2 and 5.3 of the Model Rules:
5.2 External appearance of lots
- An owner or occupier of a lot must obtain the written approval of the owners corporation before making any changes to the external appearance of their lot.
- An owner’s corporation cannot unreasonably withhold approval, but may give approval subject to reasonable conditions to protect quiet enjoyment of other lot owners, structural integrity or the value of other lots and/or common property.
5.3 Requiring notice to the owners corporation of renovations to lots
An owner or occupier of a lot must notify the owners corporation when undertaking any renovations or other works that may affect the common property and/or other lot owners’ or occupiers’ enjoyment of the common property.
It is always common courtesy to advise the Premium Owners Corporation about your renovations. Your intended change doesn’t necessarily fall under Section 5.3 above, but it is always nice to know what’s going on just in case there are any issues that may arise.
The second factor you should consider is whether or not you have additional or consolidated rules for your Owners Corporation.
Some Owners Corporations have additional or consolidated rules which are in addition to the model rules. These should always be registered (to be valid) and in keeping with the Owners Corporation’s power to make rules – Schedule 1 of the Owners Corporation Act 2006.
These rules may have conditions about external or internal window finishing’s which are in place to keep control over materials, colours or finishes. Although it can be dull from a design perspective, keeping appearances uniform for a whole building is in fact better than having a patchwork quilt scenario.
If there are no additional or consolidated rules which touch on windows, finishes or otherwise, then it appears your intended upgrade can proceed.
As always to be safe, check with your Owners Corporation manager before proceeding.