newlsie – so it sounds like your Owners Corporation specially resolved (i.e. with ≥75% of votes in favour) to permit Owners to enclose their balconies, presumably at the expense of those Owners who wished at their discretion to do so, with those expenses presumably including the costs of the roof/s to which you refer (?).
Sorry for all those presumptions, but even more clarification about precisely what form that special resolution took would be helpful, including if it was a blanket consent, what if anything was included about who pays, who’s responsible for on-going maintenance of the enclosures, about consistency of design/appearance, and about any process to have the units of entitlement of Lots altered to better reflect any improved market value accruing to those with enclosed balconies.
Irrespective of who it was intended would be responsible for undertaking and paying for the enclosures, IF those and the on-going maintenance of them once completed was originally intended to be that of individual Owners and NOT the Owners Corporation, then a concurrent Special By-Law would need to have been Registered before 2012 in order to give effect to that and indeed to any provisions such as those to which I’ve referred to about design/appearance etc.
If I was in your position, I wouldn’t be ordering windows or indeed anything else until such time as the presumptions that I’ve made here have been clarified to the satisfaction of your Owners Corporation.