With winter just around the corner your attention may turn to find the best solution to heating large indoor spaces such as warehouses, factories, workshops and industrial units.  It can be challenging to work out the most cost effective yet energy efficient method whilst adhering to workplace regulations.  

Workplace Temperatures And The Law

Workplace Regulations state that indoor working environments must be kept at a reasonable temperature.  There is no law for the minimum or maximum working temperatures, however it is recommended that a minimum of 16 to 13 degrees Celsius is adhered to if employees are carrying out physical work.  There is no recommendation for maximum temperature but employers must follow health and safety at work law which includes maintaining a comfortable temperature and providing clean and fresh air.  

What Size Heater And How Many Do I Need?

There are many things to consider when heating large spaces including the size of the room, the height of the ceilings, the number of windows and the power sources available.

There are two main measurements when it comes to heaters; wattage and BTU. A watt is a unit of power that provides one joule per second, therefore a 1000W heater will transfer one thousand joules per second. BTU stands for British Thermal Unit. It defines the amount of heat it requires to raise a temperature by one degree Fahrenheit. Heaters tend to be rated by BTU’s per hour.

It is worth bearing in mind that providing just one heater could result in uneven heat distribution with hot and cold spots within the same space. The best way to find out how many heaters you will require is to do the math.

SQUARE FEET                

  • Size of room x 10 = wattage required
  • Wattage required x 3.41 = BTUs required


  • If we had a room that was 60' x 80', this would be 2,400 sqft
  • 2400 x 10 = 24,000 Watts.
  • 24,000 x 3.41 = 81,840 BTU’s per hour
  • You could choose 2 x 13.9kW Heavy-duty heaters


  • Size of room x 111 = wattage required
  • Wattage required x 3.41 = BTU's required


  • If we had a room that was 3m x 5m, this would be 15m²
  • 15 x 111 = 1665 Watts.
  • 1665 x 3.41 = 5678 BTU's per hour
  • You could choose a 2kW fan heater.

These calculations should give you a good idea of the size of heater you require but you may need to take into account higher or even lower than average ceilings.

Heater Types

There are two main types of heaters, warm air heaters and radiant heaters.  The primary distinction between the two is that, as the name suggests, air heaters heat the air whereas radiant heaters warm objects delivering heat only where it is required.

Warm Air Heaters

  • Provide a continuous stream of warm air
  • Increase the ambient temperature of a space
  • Can run on natural gas, oil or LPG

Radiant Heaters

  • Contain a heated tube or plaque
  • Generally wall or ceiling mounted
  • Increase the heat of nearby objects and people using infra-red
  • Warmed objects them become a secondary heat source
  • Are usually powered by electricity
  • Heat can be directed exactly where it is needed

Draper Jet Force, Propane Space Heater (40,000 BTU/12kW)

Sealey IWMH1500 Infrared Quartz Heater - Wall Mounting 1500W/230V

Sealey EH2001 Industrial Fan Heater 2kW

Every space is different so no single solution will work in every working environment. We hope that this guide has helped you to consider your requirements. Here at SJ Tools, we have a wide range of heaters suitable for a variety of conditions. To browse the full range click here.


Post By Kelly Trethewey