A house has cavity walls. The cavity is filled with foam that traps many small pockets of air. Which statement best explains how this foam reduces thermal e...
Question 1 Report
A house has cavity walls. The cavity is filled with foam that traps many small pockets of air. Which statement best explains how this foam reduces thermal energy loss through the walls?
Answer Details
Trapped air is a poor conductor of thermal energy, so the many small pockets of air held within the foam reduce heat loss by conduction across the cavity. Just as importantly, because the air is broken up into many small, separate pockets, it cannot circulate freely as a single body of air, which prevents convection currents from forming across the cavity.
The foam reduces thermal energy loss mainly by trapping air in small pockets, which are poor conductors of heat and cannot set up convection currents. Without the foam, a large open cavity of air could circulate freely, carrying warm air away by convection much faster.
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