Quick Answer
Thermal mass calculation for home design involves determining the required mass of a thermal mass to store heat energy. This is usually done by calculating the heat loss of the building and matching it with the heat capacity of the thermal mass. The calculation helps ensure the thermal mass can store enough energy to maintain a stable indoor temperature.
Calculating Thermal Mass Needs
To determine the required thermal mass, calculate the heat loss of the building using the insulation requirements and climate data. For example, a well-insulated home in a cold climate might lose 10,000 Btu/h. The heat capacity of the thermal mass is typically around 0.1-0.3 Btu/lb-°F. Multiply the heat loss by the desired time period (e.g., 12 hours) to get the total energy required: 10,000 Btu/h * 12 h = 120,000 Btu.
Designing a Masonry Heater
Using the heat loss calculation, design a masonry heater with a mass of at least 2,000 pounds (around 1 ton) to store 20,000 Btu of energy. This mass can be achieved with a combination of insulation, concrete, and brick. A typical masonry heater design might use 4-6 inches of insulation, 2-3 inches of concrete, and 1-2 inches of brick. The specific design will depend on factors such as climate, building orientation, and desired indoor temperature.
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