What describes thermal mass?

• A. A type of insulation
• B. Materials that store heat, moderating indoor temperatures by absorbing and releasing heat.
• C. Materials that reflect heat
• D. A renewable energy source

Answer: (B)

Thermal mass describes materials that store heat and moderate indoor temperatures by absorbing and releasing heat. Dense materials like concrete, brick, stone, or even water can soak up heat when it’s warm and then slowly give that heat back when temperatures drop, helping to smooth out temperature swings inside a building. This can reduce the peak heating or cooling loads and improve overall energy efficiency, especially in climates with strong daily temperature changes or where passive heating and cooling strategies are used. It’s different from insulation, which slows heat transfer to keep heat from entering or leaving, from materials that mainly reflect heat, and from any energy source that generates heat.