It’s Friday morning and the boiler’s been running since half six. By nine o’clock, only 14 people are using an office with 48 desks, but the radiators are hot across the whole floor. The first question would be whether the air conditioning could heat the occupied areas without keeping every empty section at the same temperature.
The Office for National Statistics reported that 28% of working adults in Great Britain were hybrid working in early 2025. Yet plenty of heating schedules still assume everyone’s coming into the office five days a week. Tom Houlker, HVAC Expert and Director at Houlkair, writes the following article…
The Number of Empty Desks Doesn’t Tell You Much
Imagine that the office floor has four separate air conditioning zones. On a Monday, people are spread across all four, so they all need heating.
Friday’s different. Thirteen people are working near the meeting rooms, while one person has settled at their usual desk beside the north-facing windows.
Walk the floor on a few quieter days and compare where people sit with the air conditioning zones. Do this before changing the heating schedule. record which units and radiators are running in empty areas. Ask why anyone sits on their own in the office before suggesting that they move. The individual might need their particular workstation, especially if it’s adapted or has specialist equipment. But if they can move, we could test lowering the temperature in the unused zone.
Can Those Areas Actually Be Heated Separately?
Start with the building’s air conditioning drawings and compare them with what’s installed.
The number of wall controllers doesn’t always correlate to the number of independent heating zones. Some units might share a control group. I’ve serviced systems where staff change the temperature only to be overridden by the building’s management system.
Find out which indoor units serve the occupied desks, whether they can heat independently and where their temperature sensors are positioned. If a sensor is in a cold, empty room but controls units serving occupied desks, the system could keep calling for heat even after those desks are warm enough.
In a typical heat pump system there could be restrictions on running different indoor units in heating and cooling modes simultaneously. Heat recovery systems generally offer more flexibility, depending on the installation.
The radiators need looking at too. If they’re supplied by the same circuit, turning down a few radiator valves won’t necessarily stop the boiler from running. It might still be heating another floor.
I wouldn’t promise savings simply because there’s air conditioning installed. First, we need to establish what the controls actually allow.
Don’t Turn the Heating Off Completely
Take that empty northern section. It’s got external windows and possibly pipework running through it. Switching everything off throughout winter wouldn’t be sensible.
Some background heating may still be necessary to protect the building and prevent condensation. The temperature needed depends on the space and what’s inside it.
But there’s a difference between protecting an unused area and heating it to the same temperature as an occupied office.
If the air conditioning can heat the occupied sections, see whether the central heating can be turned down without affecting other areas or the ventilation. Many air conditioning units simply recirculate indoor air, so the occupied areas still need an adequate supply of fresh air. Check that changing the heating arrangements won’t interfere with this.
Check the temperature settings too. Say the radiator is maintaining 22°C while the air conditioning is set to cool above 21°C. One system could be putting heat into the room, while the other takes it straight back out.
That needs sorting before changing how the building is heated.
Test It on a Friday First
Choose a Friday when attendance is usually low and arrange for people to work in the same part of the floor, where practical. Then use the air conditioning to heat those occupied zones, with the unused areas set back to a suitable temperature.
Record the temperature near occupied desks at 9 am and again a couple of hours later, as well as when the heating starts. Note down any complaints about comfort from the team. Then, check if the boiler is still firing.
Compare the gas and electricity used over the same hours on days with similar occupancy and outdoor temperatures. Look at both energy consumption and running costs using the building’s actual tariffs. A reduction in gas use doesn’t necessarily mean an overall saving if electricity consumption increases significantly.
Repeat the test on a few comparable days before changing the heating arrangements permanently.
Some buildings won’t have the controls to make this worthwhile. But if we’re still heating a floor for 48 people when only 14 turn up on Fridays, I’d want to know whether we could do things differently with the equipment already installed.
