A thermal model is a 3D computer simulation that can predict how the temperature in a building will vary from room to room, day and night and through the seasons.
Sustainable design for comfort
In a well-ventilated building, humans find an ambient temperature of about 20°C comfortable. Choosing the right materials and structures allows engineers to smooth out temperature variations and use the natural day-night heating and cooling cycles of the building to minimise the need for artificial heating, cooling and air conditioning.
At the Institute of Physics building in London, the design incorporates large concrete slabs. During the day, sunlight through the window warms the concrete. After sunset, the building starts to cool. Lots of concrete was incorporated into the design because it has a high thermal capacity which means that, when compared to other building materials, it can store more energy per degree rise in temperature.
As well as taking longer to warm up during the day, this means the concrete takes longer to cool at night. The slabs stay warm and so provide free heating for the rest of the building well into the night; a real advantage when you want to reduce the heating bill in winter.
In hot weather the high thermal capacity of the concrete could lead to overheating. This is alleviated by incorporating vents, which allow hot air to be flushed out naturally. When the vents are opened, warm air rises up through the centre of the building through an atrium; this sucks in the cooler air from outside, cooling the lower spaces. Opening these vents also reduces the need for air conditioning in summer.
What is a thermal model?
A thermal model is a 3D computer simulation that can predict how the temperature in a building will vary from room to room, day and night and through the seasons. Each thermal model has to be bespoke to take account of the local conditions such as variations in ground temperature and orientation of the plot (south-facing walls absorb more sunlight than north-facing ones). By running year-long simulations and trying out different materials and positions for walls, windows, ceilings and roofs, engineers can choose a design that is optimal.
As well as minimising the carbon footprint of a building, computer simulations are also being used to fight climate change on a larger scale. Virtual models of the whole Earth, run on supercomputers, allow climate scientists to run 100-year simulations with different levels of greenhouse gases to make predictions about global temperatures.
- Discover more about the physics behind the IOP’s King’s Cross home in a feature from Physics Review (PDF, 1MB). (Originally published November 2019 and reproduced with kind permission of Hodder Education.)