The Heating and Cooling Loads feature was designed following the specifications of the ASHRAE Handbook of Fundamentals. There are several ways to determine peak loads, and the one that this feature adheres to is the RTS (Radiant Time Series) method. This method takes into account the time delay effect as heat is transferred from the outside, through envelopes, and into spaces. For a more thorough description, see Calculation. The application used to calculate heating and cooling loads reports is referred to as the engine.