Architects pride themselves on their ability to design buildings that operate at a high level of occupant satisfaction. Yet the complex interplay of variables, which can’t always be predicted or managed, may create the perception that these buildings are not performing as advertised. The building owner might not service a high-performance building's heating and cooling systems regularly; tenants may set thermostats too low or high, or leave the doors and windows open at inopportune times; or an unexpectedly cold winter could diminish a building's advertised efficiency.