With the developments in the technology of heating and air conditioning, it is easy to assume that HVAC units are relatively new. This is not the case as this essential household appliance has been around for many years. 
Older HVAC Technology:
There have been various heating, ventilation and air conditioning systems employed in homes around the world throughout recent history. Fireplaces and wood burning stoves were a popular form of heating for hundreds of years, with open windows providing ventilation and cooling. By the early 1830s, basic forms of air conditioning had been developed to ensure that homes and properties feel more comfortable in hot summer months. The most notable example of this was the apparatus invented by American Doctor John Gorrie. This early air conditioner fanned air cooled by containers of ice into patients’ rooms.
Modern Air Conditioners:
Willis Carrier is credited as inventing the first modern system. Carrier was from upstate New York and trained as a mechanical engineer. He was inspired to invent an air conditioning unit on a foggy night while waiting for a train in Pittsburgh. This situation led him to assess the relationship between humidity, dew point and the temperature. Carrier went on to create a system and found the Carrier air conditioning company.
The air conditioners created by the Carrier air conditioning company used his observations and not only lowered the temperature but decreased air humidity. These units were installed in factories, hospitals and other various buildings with far reaching results. The development of “manufactured air” and the ability to cool down the temperature inside a building contributed to advancements and improvements in a number of industries including textiles, beer and food.
Development of the Initial Design:
The initial air conditioner units produced by Carrier were large, costly and made use of the highly toxic chemical ammonia for a coolant. Improvements were made to later designs to use other safer chemicals instead of ammonia such as dielene or dichloroethylene. The development of the design also allowed for the decrease in size of the units. Reducing the size of the unit created more flexibility and provided the opportunity for air conditioning to be installed in more buildings.
Carrier also presented the American Society of Mechanical Engineers with the Rational Psychrometric Formula. This formula was a theoretical discussion about the artificial regulation of atmospheric moisture and potential solutions to govern atmospheric moisture conditions. This formula is still in use to calculate cooling the air with an understanding of the relationship between humidity and temperature.
Heating Systems:
The first low-pressure heating system was developed by James Trane in 1885. Trane was a Norwegian immigrant who lived in Wisconsin. This initial design was further improved when Trane’s son Reuben invented the convector radiator. These innovations were used to heat homes and buildings and would be an integral aspect of the Trane company developing efficient heating solutions for buildings.
The Trane company would later become involved in air conditioning, inventing the Turbovac. This device was a centrifugal, hermetic refrigeration machine, used to cool buildings.
With the development of these innovations, the modern HVAC system could be born. Over the years, modern HVAC systems have been further refined to create an effective method of heating and cooling a home without it costing the earth.