Free tool
How warm is a container in winter?
To keep it at 20 °C inside you need
1.7 kW
— about one 2 kW oil-filled radiator.
per hour
per 8-hour day
W per °C
Steady-state estimate: fabric heat loss plus 0.5 air changes an hour, 2.4 m ceiling, electric heating at 100% efficiency (a heat pump uses roughly a third). Sun, wind and door opening change real costs.
Where the numbers come from
Heat escapes through every surface. How fast depends on its U-value — the watts lost per square metre for each degree of difference between inside and outside. Lower is better.
- Roof: 0.26 W/m²K — 125 mm EPS (50 mm PUR on some ranges).
- Walls: 0.46 W/m²K — 50 mm EPS sandwich panel (PUR option).
- Floor: 1.24 W/m²K — 2 mm PVC vinyl on 14 mm cement board. The floor loses the most, so a raised, insulated base or a rug makes a real difference.
- Windows — PVC, double glazed, 90° opening.
We add the heat needed to warm fresh air (half the air changed each hour) and assume a 2.4 m ceiling. The result is the steady heat you need once the room is warm; allow a little extra to warm it up from cold.
Planning a cabin for a site or a gate? See site cabins, container offices and security cabins, and check when you need planning permission.
Straight answers
Questions buyers ask us
Is a container office warm enough to work in all winter?
Yes, with heating. A 3 × 7 m unit needs about 1.7 kW to hold 20 °C when it is −5 °C outside — one oil-filled radiator or a small heat pump.
Can I upgrade the insulation?
Yes. PUR panels and rock-wool (non-combustible) panels are available, and a raised insulated floor cuts the biggest heat loss.
What about condensation?
Keep it heated and ventilated. The windows open 90° and we fit trickle ventilation; a small dehumidifier helps in a cabin that is used only occasionally.
Not sure which one? Ask us.
Tell us what it's for, where it's going and roughly when. We reply with a written quote by email.