A building with good thermostatic control means the heating system warms up the building to the set temperature and then maintains it at a constant level. The heating required, and therefore gas consumption, varies linearly with how cold it is outside. The heating system can adjust for internal heat gains due to people, electrical equipment and sunshine warming the building. It can also adjust for losses due to ventilation. Poor thermostatic control is likely to cause poor thermal comfort (users feel too hot or too cold), and excessive gas consumption as the thermal comfort is often maintained by leaving windows open.
Unfortunately, many schools have poor thermostatic control. This can be due to poorly located boiler thermostats. A common location for a thermostat in schools is in the school hall or entrance lobby whose heating, internal gains and heat losses are not representative of the building as a whole, and particularly classrooms. Halls are often poorly insulated with few radiators which means they never get up to temperature, causing the boiler controller to run the boiler constantly and the better insulated classrooms to overheat.
Poor thermostatic control can also be due to a lack of thermostatic controls in individual rooms which leads to windows being opened to compensate.
Fixing thermostatic control issues can be difficult but it can make a school more comfortable and save money.
Overly hot classrooms
The ideal temperature range for learning is 18C for normal classrooms, 15C for area of the school with high levels of activity (e.g. sports halls) and circulation spaces (e.g. corridors) and 21C for Special needs schools, low activity areas or areas with very young children. Above and below these temperatures, students’ learning performance reduces. As a rule of thumb, for every 1C increase in classroom temperature, there is a 10% increase in gas consumption.
Energy Sparks recommends a classroom temperature for most schools of 18C which reduces gas consumption and provides a good learning environment for students. We often find when visiting schools that some classrooms are too hot (above 23C) which is both detrimental to students’ alertness and is more expensive to heat. We also find that thermostatic radiator valves (TRVs) are not adjusted correctly and set to their maximum settings. When a classroom gets too hot, rather than being turned down, windows are opened.
FIxing this in an existing school is difficult and is best dealt with through behavioural change which could include:
- a prominently displayed large thermometer in each classroom, with a recommended temperature drawn on it, which pupils can monitor
- a school or eco-team exercise to measure classroom temperatures and present the results to the whole school
- a weekly or monthly check by the caretaker or building manager of all TRVs to make sure they are not set to maximum
Suggestions for improving thermostatic control include:
- making sure that TRVs are not set to maximum and avoid opening windows to reduce classroom temperatures. If windows are opened to control temperature, then in milder weather, there will be a drop in gas consumption
- ensuring that the main thermostats for the boiler are well positioned in locations which are representative of the majority of the school’s rooms e.g. classrooms rather than in halls or corridors
- install weather compensation on your boiler (see below)
Most modern school boilers support ‘weather compensation’ which is often the best way of maintaining good thermostatic control across the whole school. Weather compensation reduces the temperature of the water circulating through the pipework from 80C in colder weather to perhaps 45C in milder weather and, as a result, automatically changes the heating output of the radiators.
This means the thermostatic control in individual rooms is less reliant on the TRV settings. It also means classrooms are less likely to overheat in milder weather and can save a significant amount of energy. Most commercial boilers already support weather compensation, but it is often not enabled in schools. Energy Sparks recommends that a school checks with their boiler service engineers whether this is enabled at their school next time their boilers are serviced.
Covid ventilation and keeping warm
Providing adequate ventilation does not mean people have to work in an uncomfortably chilly school. There are simple steps you can take to make sure your school is adequately ventilated without being too cold:
- Partially opening windows and doors can still provide adequate ventilation
- Open higher-level windows to create fewer draughts
- If the area is cold, relax uniform codes so people can wear extra layers and warmer clothing
- Regularly open windows and doors when people leave for a break. Even 10 minutes a hour can help reduce the risk of the virus circulating in the air, depending on the size of the room