Comparison tests are described that show people will accept spaces being cool upon entry if the spaces can be brought quickly to a comfortable level with radiant heat. Subjects from a comfortable area at 22°C (72°F) entered a space at 15°C (59°F) and occupied it for two hours. After the subjects’ entry, spot radiant or fast-acting radiant ceiling panels rapidly raised the operative temperature of the space to 22°C. A sensor that averaged air and mean radiant temperatures was found to be superior to an air temperature sensor as input to the radiant heat controller. It produced less operative temperature overshoot and greater occupant thermal acceptability and reduced power consumption. There are numerous applications for energy savings with fast radiant systems, particularly where there is intermittent occupancy. The technique and control are also applicable to steady state situations. The savings depend on the application and can be predicted by calculation from the response characteristics of these tests.