Factors for electric heating in building design

Electric space heating of a building should keep rooms comfortable with the minimum heating load and energy cost. The heater rating depends on the heat lost from the building, so the design must reduce losses and use heat well.

Factors to be considered

1. Heat loss by conduction (fabric loss): loss through walls, roof, floor, windows and doors, $Q = U A \Delta\theta$. Use materials with low thermal transmittance (U-value) and add insulation, especially in the roof.
2. Ventilation and infiltration loss: heat carried away by air changes, $Q = 0.33\,n\,V\,\Delta\theta$ W (n air changes per hour, V room volume in m³). Seal cracks and use weather-stripping but keep enough fresh air.
3. Windows and glazing: glass loses heat fast; use double glazing, curtains, and suitable window area.
4. Orientation and solar gain: face main rooms and windows to the south (in Nepal) to gain winter sun; shield from cold winds.
5. Thermal capacity (mass) of the building: heavy walls store heat; good for storage heaters charged at off-peak hours and for steady temperature.
6. Design temperatures: required indoor temperature (about 18–22°C for living rooms) and lowest outdoor temperature of the site decide $\Delta\theta$ and heater size.
7. Occupancy and internal heat gains: heat from people, lights and appliances reduces the heating need.
8. Type and placement of heaters: convection, radiant, under-floor, storage or heat-pump systems; place heaters near cold surfaces (under windows) for even temperature.
9. Controls: thermostats, timers and zone control avoid overheating and waste.
10. Tariff and supply: time-of-day tariff favours off-peak storage heating; wiring and protection must suit the heating load.

   heat in (heater)  -->  room at 20 C
        |                    |
        |    losses: walls, roof, floor,
        |    windows, air leakage
        v                    v
   heater kW = fabric loss + ventilation loss
               - internal gains

Good insulation, air tightness and correct heater sizing together cut both the connected load and the running cost.