Thermal mass

Thermal mass is like a big battery that stores heat energy. Imagine you are outside on a sunny day and you touch a metal slide on the playground. It feels really hot, right? But if you touch a wooden bench that's been in the sun, it feels warm but not as hot as the metal slide. That's because the metal slide has a low thermal mass and heats up quickly while the wooden bench has a higher thermal mass and takes longer to get as hot.

Buildings can use thermal mass to their advantage in order to stay warm or cool without using a lot of energy. For example, if a building is made of materials like stone or concrete, they have a high thermal mass and can store a lot of heat energy. During the day, the sun shines on the building and heats up the walls and floors. At night, when the air outside gets cooler, the heat stored in the thermal mass is released and keeps the building warm without the need for extra heating.

Similarly, in the summer, the same thermal mass can help keep a building cool. During the day, the walls and floors absorb heat from sunlight, keeping the inside of the building cooler. At night, when the air outside is cooler, windows can be opened to let in the cool air and allow the heat in the thermal mass to escape, keeping the building comfortable without the need for air conditioning.

So, thermal mass is like a big battery that stores heat energy and can help buildings stay warm or cool without using a lot of extra energy.