Heat Gain and Loss

Can you explain how a home gains heat? How does it lose heat?

Heat gain is the total increase in the internal temperature of a building due to exposure to solar and ambient heat sources. Heat gain is primarily due to a building’s exposure to the sun. As sunlight strikes the surfaces (roof and walls) of a home it is converted to heat and permeates into the home. Windows, however, transmit sunlight directly into the interior of a building, converting sunlight to heat as it strikes furnishings or floors. A building may also gain a slight amount of heat from ambient external sources such as the actual outdoor temperature and nearby objects, or indoor sources such as appliances, artificial lighting, and people.

The opposite of heat gain is, of course, heat loss; instead of heat entering a building, it is attempting to escape. Heat naturally flows towards cooler spaces; interior heat will try to flow through windows, walls, and ceilings into the cool environment.