HVAC Systems in Buildings: Fundamentals

About this course.

HVAC — heating, ventilation and air conditioning — is the collection of building services that make the inside of a building comfortable and healthy to occupy by controlling its temperature, its humidity, the movement and freshness of its air, and the removal of stale air and pollutants. It matters for three reasons that run through this whole course: comfort, because people work, rest and live better in conditions that are neither too hot nor too cold nor too stuffy; health, because the air people breathe indoors, and the moisture and pollutants in it, directly affect wellbeing; and energy, because HVAC is frequently the largest single energy user in a building, so how well it is designed and run has a major bearing on running costs and emissions. Good HVAC delivers all three together; poor HVAC compromises comfort, health and efficiency at once.

The three letters describe three related jobs. Heating adds warmth when the building would otherwise be too cold. Air conditioning, in the strict sense, controls the indoor environment — most commonly by cooling and, often, by managing humidity, but the term is widely used to mean cooling. Ventilation supplies fresh outside air and removes stale indoor air along with the moisture and pollutants it carries. In practice these functions overlap and are frequently delivered by integrated systems, but it helps to keep them distinct in the mind, because a building can be warm yet stuffy, or cool yet humid, if one function is provided and another neglected. A complete approach to the indoor environment addresses temperature, humidity, air freshness and air movement together.