Deloitte has reduced temperatures in its UK offices in a bid to save costs and cut carbon emissions.
Thermostats are being turned down by 2C across 22 sites, some of which were also temporarily closed over Christmas.
The Big 4 firm told staff the change in temperature is expected to result in savings of about £75,000 for December alone.
Offices are now be heated to between 19 and 22C which is still above the minimum 16C guideline from the Health and Safety Executive.
Deloitte revealed that the savings from December will be donated to disability charity Scope
Both KPMG and PwC also temporarily shut down some of their offices over the festive period too to help cut costs.