What is the difference between passive and active solar design strategies?

• A. Active solar uses building form and materials to collect/store heat; passive uses mechanical systems.
• B. Passive solar uses PV panels for energy; active uses natural light.
• C. Passive uses building form and materials to collect/store heat; active uses mechanical systems like solar collectors or PV to harvest energy.
• D. Active and passive are identical.

Answer: (C)

The difference lies in how solar energy is captured and used in the building. Passive solar design relies on the building’s form, orientation, materials, insulation, glazing, and shading to collect, store, and distribute heat with little or no mechanical help. Think south-facing windows, concrete or masonry mass to store heat, and natural ventilation to regulate temperature. Active solar design, on the other hand, uses mechanical or electrical systems to harvest solar energy, such as solar collectors or photovoltaic panels, along with pumps, fans, or other equipment to move heat or generate electricity.

So, the best answer states that passive uses building form and materials to collect/store heat, while active uses mechanical systems like solar collectors or PV to harvest energy. The other options mix up what collects energy or how it’s used, or claim the two are the same, which isn’t correct.