A new concept for perimeter energy control in buildings is described. Unlike conventional perimeter heating systems, which utilize temperature control, this system measures real-time heat flow through the building envelope and modulates the perimeter heat directly proportiona/ to the measured loss (U.S. Patent No. 4,274,475). This allows rapid adjustment for perimeter heat loads due to wind skin effects, snow, rain, sleet, and solar gain. Space air temperature is maintained by the conventional air-handling system; only perimeter make-up heat is based on heat flow.

A test installation that resulted in average energy savings for the perimeter heating system of 25% to 30% with maximum savings up to 58% is described. Applications of the concept to replace indoor/outdoor air temperature control systems for use with various types of perimeter heat are described. Applications of the concept to cool- ing systems are also discussed.