A great many existing reheat-type HVAC systems are in use today. Most of these could be retrofitted to conserve energy in fairly simple ways. This paper summarizes some of the more commonly used present-day techniques. These include the use of discriminators, addition of economy-cycle outside air control, conversion of constant volume systems to variable air volume (VAV), and other methods. In making these changes it is necessary to avoid unnecessary complexity and avoid effects detrimental to the building environmental control.