Mechanical services and controls have a large impact on the energy performance of a building, typically as much as the fabric. Clearly, the potential for improvement will depend on the current state of the mechanical equipment, which typically is updated more frequently than the building fabric. However, even recent services upgrades may not have attended in particular to improving energy performance.For example, it is not uncommon to see new low energy light fittings providing higher than necessary illuminance levels, and without controls, where no saving or even increased energy consumption is the result.