In our last blog about sustainable CRE, we looked at the value of investing in environmentally sustainable buildings. This time, we’re going to focus on one of the challenges of building a sustainable CRE portfolio: namely, how to ensure your tenants use your building in an environmentally-conscious way.Whether you are a CRE landlord, owner, investor or asset manager, this should be of interest to you. Why? Because the activities of occupiers could make up as much as 70-80% of a building’s total carbon footprint (source: EG). So even if you have a host of green building certifications and have installed super-efficient main building services , how your building performs depends significantly on how your tenants operate within it.This is known as the ‘'performance gap’: the difference between how a building should perform when it’s designed, and how it actually does perform when it’s occupied.