|
Heat flows from a hot or warm medium to a cold medium in three ways:
- By radiation from a warm surface to a cooler surface through air or a vacuum using infra-red heat rays
- By conduction through solid or fluid materials resulting from direct contact
- By convection, which involves the physical movement of air - warm air rises
Heat moves through wall cavities or between roofs and attic floors by a combination of radiation, conduction, and convection with radiation being the dominant method of heat transfer. Research shows that control of radiant heat transfer is the core of heating/cooling climate control.
Radiation is accounts for 65-85 percent of all heat transfer through walls, ceilings, attic and floors. Reflective insulation is an effective barrier against radiant heat transfer because it reflects back almost all of the infrared radiation striking its surface and emits very little of the heat conducted through it. Reflective insulation products also incorporate trapped air spaces as part of the system to retard the convective flow of heated air the same way fiberglass insulation does.
|