floor (i.e. the foundation), the above-grade walls, the roof, and the windows and doors. the envelope separates our indoor environment from the weather outside. to maintain our indoor environment, the envelope must control the flow of heat, air and moisture from the inside to the outdoors.
heat will move wherever there is a difference in temperature. many people believe that because hot air rises, most heat loss will be through the ceiling. this is not necessarily so. heat moves in any direction – up, down or sideways – as long as it is moving from a warm spot to a colder one.
2.1.3 how does heat flow?
heat flows in three distinct ways. 