Building automation is becoming an increasingly important aspect in the design of green buildings, because of the energy-efficiency improvements it can bring. Early consideration in the design process is essential for full benefit. EN 15232, "Energy Performance of Buildings. Impact of Building Automation, Controls and Building Management", identifies four classes for building automation: A (highly energy-efficient) to D (not energy-efficient). Many facility managers have been implementing technical building management systems for years and making a key contribution to sustainability. Investors, too, are keen to include real life-cycle costs in their calculations of return. In the future life-cycle costs will be available for every building, thanks to certification systems like the Gebäude-Energieausweis and the Deutsches Gütesiegel für Nachhaltiges Bauen (German Sustainable Building Certification).