Which of the following is an example of a thermal bypass?

A thermal bypass refers to a path that allows air to flow through the building envelope, usually leading to heat loss or gain, which can undermine the efficiency of a building's heating and cooling systems. In this context, an un-insulated cantilever is an excellent example of a thermal bypass because it extends beyond the conditioned space and can create gaps or unsealed areas that allow air movement. This uninsulated component can contribute significantly to heat transfer, causing drafts and making it difficult to maintain comfortable interior temperatures.

The insulated attic option does not represent a bypass since it is intended to limit thermal transfer. Sealed ductwork also does not serve as a thermal bypass; instead, it is designed to ensure that heated or cooled air travels efficiently throughout the living spaces without loss. A radiant barrier reflects heat instead of allowing it to transfer into or out of the building; therefore, it serves to mitigate heat gain or loss rather than facilitating the bypassing of thermal control zones.