Page 240 - Masonry and Concrete

Footings, Foundation Walls, Basements, and Slabs
239
FOOTINGS, FOUNDATION WALLS, BASEMENTS, AND SLABS

and not under the entire floor area. Placing this insulation vertically
on the outside of the foundation provides the greatest protection from
freeze-thaw stresses. Recommended R-values for perimeter insulation
are shown in Figure 6-45.
Heat loss from a basement includes that which takes place through
the wall above grade and that which takes place through the wall and
floor below grade. In addition, there is heat loss in the movement of
air. There is a potential path of significant air leakage through the joint
between the top of the basement wall and the sill plate of the super-
structure. With a hollow concrete block wall, part of which is exposed
above grade, air in the block cores is cooled and sinks by convection,
displacing warmer air in the lower parts of the wall. This causes addi-
tional heat loss from the basement as the lower portions of the wall are
cooled. Insulating the outside of the wall will minimize this effect, and
grouting the wall will eliminate the convective air spaces. Except in
extreme northern climates where the ground temperature is colder, it
is usually necessary to insulate only the first 3 to 6 ft. of below-grade

HEAT FLOW LINES

LINES OF
CONSTANT
TEMPERATURE
(ISOTHERMS)

FIGURE 6-43
Radiant heat loss to soil. (from Donald Watson and Kenneth Labs, Climatic Building
Design, McGraw-Hill, 1983).

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