Office thermal comfort by the numbers
CIBSE Guide A and TM52 frame office thermal comfort around operative temperature and the predicted percentage dissatisfied (PPD). In practical UK terms, that means 21–23°C in winter and 22–25°C in summer, with relative humidity held between 40% and 60%. Outside that humidity band, dry-eye and respiratory complaints rise above 40%, dust mite and microbial risks rise above 60%.
How we monitor office temperature and humidity
Continuous temperature and humidity sensors (±0.3°C, ±2% RH accuracy) are deployed across representative zones at desk height, away from supply diffusers and external glazing where local readings would mislead. Twelve months of data captures the seasonal extremes that drive most complaints — the cold January perimeter zones, the August afternoons when the AHU cooling coil cannot keep up.
What the data typically reveals
Common findings include winter humidity below 25% across the whole floor (drives the dry-eye and 'cold I keep catching' complaints), summer perimeter overheating from solar gain, and stratification of 4–5°C between desk height and ceiling diffuser. None of these are visible on the BMS dashboard, which usually reads from a single zone temperature sensor in the return air duct.
Engineering action
Humidification upgrades, solar-gain mitigation (films, blinds, automated shading), supply temperature reset, and rebalancing supply between perimeter and core all improve measured comfort. We sequence interventions against the data and re-measure to verify the outcome.
Frequently asked questions
What temperature should an office be in the UK?
CIBSE Guide A: 21–23°C in winter, 22–25°C in summer. The Workplace Regulations 1992 set a legal minimum of 16°C (13°C for physically active work).
What is the ideal office humidity?
40–60% relative humidity. Below 30% RH drives dry-eye and respiratory complaints; above 70% RH increases microbial and dust-mite risk.
Why is one side of our office always cold?
Almost always a combination of perimeter heat loss through glazing and underperforming supply at the perimeter zone. Continuous monitoring quickly identifies whether the issue is fabric, supply, or controls.