Convection is the transfer of heat by physically moving the molecules from one place to another. A campfire can warm you even if there is wind between you and the fire, because radiation is not affected by air. With buildings, we refer to heat flow in a number of different ways. R-values are measured by testing laboratories, usually in something called a guarded hot box . So far, so good.
Heat capacity is a measure of how much heat a material can hold.
As typically used in energy performance computer modeling, heat capacity is determined per unit area of wall. In the following section, we will examine how the heat capacity of materials can affect the energy performance of buildings. Let's take a look at a typical use of one of these high-mass materials in a wall system. When one side of the wall is warmer than the other side, heat will conduct from the warm side into the material and gradually move through it to the colder side. In real-life situations, however, the inside and outside temperatures are not constant.