Step by Step tutorial outlining root top air conditioning and heating units. A Roof Top Unit, or RTU is placed on the roof of a commercial or residential construction project.
Air conditioning is the process of altering the properties of air (primarily temperature and humidity) to more favorable conditions. More generally, air conditioning can refer to any form of technological cooling, heating, ventilation, or disinfection that modifies the condition of air.
An air conditioner (often referred to as AC) is a major or home appliance, system, or mechanism designed to change the air temperature and humidity within an area (used for cooling and sometimes heating depending on the air properties at a given time). The cooling is typically done using a simple refrigeration cycle, but sometimes evaporation is used, commonly for comfort cooling in buildings and motor vehicles. In construction, a complete system of heating, ventilation and air conditioning is referred to as "HVAC".
The basic concept behind air conditioning is known to have been applied in ancient Egypt where reeds hung in windows had water trickling down. The evaporation of water cooled the air blowing through the window, though this process also made the air more humid. In Ancient Rome, water from aqueducts was circulated through the walls of certain houses to cool them down. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool buildings during the hot season. Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1911 by Willis Haviland Carrier. The introduction of residential air conditioning in the 1920s helped start the great migration to the Sunbelt.