Heating for comfort#

We heat buildings mostly to make the people who use them comfortable.

Because we’re used to controlling heating with thermostats, and they measure air temperature, most people think air temperature is the only thing that matters. In buildings that are well-insulated, dry, draughtproofed, and in high use, air temperature is a really good indicator of how comfortable people in the building will feel. That’s less true of buildings that are leaky or not heated all the time. In these buildings, it’s very important to understand what makes people feel comfortable.

The other things that matter are:

  • Temperature of surrounding surfaces (mean radiant temperature). We’re all familiar with what heat radiating to us from the sun feels like. When we’re surrounded by cold surfaces, the opposite happens - heat radiates from us to the surfaces, making us feel cooler. “Mean radiant temperature” is just as important to thermal comfort as air temperature.

  • Draughts. Even a warm draught feels cold. Women tend to feel draughts more keenly than men do.

  • Relative humidity. This is the amount of moisture the air has compared to the total amount of moisture it can hold, which varies with the temperature of the air. The warmer the air is, the more moisture it can hold. Relative humidity has a range from 0-100%. When it reaches 100%, moisture falls out of the air. The damper a building is, the colder it will feel.

  • How active the occupants are (metabolic rate). If people are running around, they will be comfortable at lower temperatures.

  • Clothing levels. Up to a point, more layers of clothing and materials like wool that trap air will also make people comfortable at a lower temperature.

six elements of thermal comfort, namely, air temperature, radiant temperature, humidity, air speed, metabolic rate, and clothing level

Image Source: November 2018 LinkedIn post by SimulationHub, (88) Role of CFD in Evaluating Occupant Thermal Comfort

Top Comfort Tip

One of the most important things you can do is ensure consistent, non-draughty conditions so your building’s users know how much clothing to bring and don’t have to keep changing it while they are in the venue. People are very adaptable as long as they can predict what they need to do. That makes having the right heating controls very important.