Thermal mass is the ability of an object or material to absorb, store, and release heat. It is a key concept in the temperature control of buildings and objects, essentially determining how long it takes for the temperature to change in a given environment.
What determines thermal mass?
Mass: The greater the mass of a substance, the more heat it can store.
Specific heat capacity: The property of a given substance that shows how much energy is required to change the temperature of 1 kg of the substance by 1 °C.
Material type: Denser materials, such as concrete or stone, generally have a higher thermal mass than lighter materials, such as wood or glass.
Thermal mass in architecture
The thermal mass of buildings greatly influences the stability of internal temperatures, the efficiency of heating and cooling systems, and energy consumption.
Buildings with high thermal mass:
- They heat up slowly and cool down slowly.
- They provide a more stable internal temperature.
Advantages:
- They reduce daily temperature fluctuations.
- They can be energy efficient by utilizing passive solar energy .
Disadvantages:
- They respond more slowly to changes in heating or cooling demand.
Low thermal mass buildings:
- They heat up quickly and cool down quickly.
- They are less able to store heat.
Advantages:
- They respond more quickly to temperature changes.
Disadvantages:
- Due to their smaller heat storage capacity, the impact of external temperature fluctuations is greater.
Thermal mass and energy efficiency
Proper utilization of thermal mass can significantly improve the energy efficiency of a building.
Passive thermal control: In buildings with high thermal mass, walls and floors absorb solar energy during the day and release it at night, minimizing the need for heating.
Cost reduction: Energy-efficient thermal control reduces heating and cooling costs.
Sustainability: High thermal mass reduces energy consumption, contributing to a lower carbon footprint.
Examples of different thermal masses
| Material | Thermal mass (MJ/m³°C) | Application |
|---|---|---|
| Concrete | 2.0–2.5 | High thermal mass buildings, industrial floors |
| Brick | 1.6–2.0 | Walls of traditional buildings |
| Wood | 0.5–1.0 | Low thermal mass structures |
| Glass | 0.8–1.0 | Windows, low heat storage capacity |
Thermal mass optimization
Material selection: When selecting building materials, their thermal mass and role in the building must be taken into account (e.g. brick, concrete, wood).
Orientation: Large glass surfaces with a south orientation allow for the absorption of solar energy, which can be stored in materials with high thermal mass.
Insulation combination: High thermal mass combined with proper insulation effectively reduces heat loss.
Integration of heat pump systems : Thermal mass can be utilized in conjunction with modern heat pump systems to provide balanced temperatures throughout the building.
Summary
Thermal mass is the property of buildings and materials that determines how they respond to temperature changes. High thermal mass ensures a stable indoor climate and energy-efficient operation, while low thermal mass can respond to rapid temperature changes. Material selection, insulation and proper design are key to optimally exploiting thermal mass, which can contribute to reducing energy consumption and increasing sustainability in buildings.