How much fuel do furnace door openings waste, and how do I measure it?
Every minute a hot furnace door stands open, radiant heat escapes and cold air rushes in, so burners fire harder. Log door-open minutes for a few weeks, compare fuel per tonne on low and high days, then fix with faster doors, curtains or smaller charging openings.
Where the loss comes from
- Radiation straight out of the opening, worst at high furnace temperatures.
- Cold air drawn in, which the burners then heat to furnace temperature.
- Longer cycle times when the charge cools near the door.
How to measure it
- Record door-open minutes per shift, with a simple switch counter or a logbook.
- Read fuel per tonne from the same shifts, using fuel invoices or a meter.
- Compare shifts with low and high open time; the difference per tonne is your estimate.
Fixes that usually pay
- Quick-acting doors and good seals.
- Ceramic fibre curtains at charging openings.
- Charging in batches so the door opens fewer times.
What Senseible does here
Senseible reads fuel invoices and electricity bills and applies IPCC 2006 factors and the CEA grid factor (0.710 kg CO2 per kWh), so you can compare Scope 1 and 2 before and after a change from the documents themselves.
Sources: 2006 IPCC Guidelines, Volume 2 Energy, Bureau of Energy Efficiency, GHG Protocol Corporate Standard
Last reviewed 2026-10-22.