What does the term "thermal envelope" encompass in building design?

The term "thermal envelope" refers to the barrier that separates conditioned space, which is heated or cooled, from unconditioned space, which is not. This barrier is crucial in building design as it directly affects the energy efficiency of a building. The thermal envelope includes elements such as walls, roofs, floors, windows, and doors, all of which work together to control heat flow into and out of the building.

In a well-designed thermal envelope, these components are properly insulated and sealed to minimize heat loss in the winter and heat gain in the summer, thus maintaining indoor comfort levels without excessive energy use. By effectively managing the thermal envelope, buildings can reduce heating and cooling demands, leading to lower energy consumption and costs.

While the other options may have relevance to energy management and efficiency, they do not encompass the full scope of what the thermal envelope entails. The focus is specifically on the physical barrier that regulates internal environmental conditions, making the chosen answer the most accurate representation of the term within the context of building design.