I think there is no general number, because it really depends on which sector of the building industry you are dealing with. Commercial owners, for example, are very much business-driven. They make improvements, and they try to recoup those investments. In the public sector, they own buildings for a very long time.
We would suggest to work with the provincial governments, or in this case, the Office of Energy Efficiency at Natural Resources Canada, and ask what the best proposal is for each of these subsectors.