I can't give you a definitive answer on that one, because I don't have access to the analysis. The National Capital Commission could give you that.
I have been informed, through other activities in industry and real property sectors, that when you do go towards greening, there may be an additional cost at the beginning that will be incurred, with the offset of greener facilities on a go-forward basis. Depending on the amortization period, it may not be that much more expensive.
In this case, again, the National Capital Commission would be able to provide you with a response more specific to this building.