I don’t believe that the OC is obliged to install insulation, more specifically there is no requirement that an OC install insulation – perhaps a better approach is for you to offer to pay for part of it, and persuade the other owners who will benefit to also pay.
You may also be asked to agree to a special by-law making you responsible for the insulation.
I had insulation installed some time ago as I am on the top level, and it made a huge difference.