---
title: "Factors for electric heating in building design"
subject: "Utilization of Electrical Energy"
chapter: 5
key: "semester_7/utilization_of_electrical_energy:electric-heating-building-design-factors"
source: https://www.bctengineer.com/q/semester_7/utilization_of_electrical_energy/electric-heating-building-design-factors
site: BCT Engineering
---

# Factors for electric heating in building design

Utilization of Electrical Energy · Chapter 5: Electric Heating

- Asked in: 2071 Shrawan
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/utilization_of_electrical_energy/electric-heating-building-design-factors
- Whole chapter: https://www.bctengineer.com/md/semester_7/utilization_of_electrical_energy/chapter-5

## Question

Discuss the various factors to be considered for electric heating in building design.

## Short answer

Key factors are fabric heat loss, ventilation loss, glazing and orientation, thermal mass, design temperatures, internal gains, heater type and placement, controls, and tariff. Reduce conduction with low U-value insulation and seal infiltration while providing controlled fresh air. Correct sizing and controls minimise energy cost.

## Answer

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.

```text
   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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Fabric (conduction) heat loss is given by:
   A. Q = 0.33 n V Δθ
   B. Q = U A Δθ
   C. Q = m c Δθ
   D. Q = P t
   Answer: B. Loss through walls, roof, floor and windows is U x area x temperature difference. (Key point: Conduction loss)

2. In Q = 0.33 n V Δθ, what is n?
   A. Air changes per hour
   B. Number of rooms
   C. Number of heaters
   D. Wall thickness
   Answer: A. n is air changes per hour and V is room volume, so seal cracks yet keep fresh air. (Key point: Ventilation loss)

3. The heater kW should equal:
   A. Fabric loss only
   B. Internal gains only
   C. Ventilation loss x 2
   D. Fabric loss + ventilation loss - internal gains
   Answer: D. Occupants, lights and appliances give heat that reduces the heating need. (Key point: Heater sizing)

4. Why face main windows south in Nepal?
   A. To avoid sunlight
   B. To increase infiltration
   C. To gain winter sun
   D. To raise U-value
   Answer: C. South-facing glazing gives solar gain in winter, reducing the heating load. (Key point: Orientation in Nepal)

## Related in Utilization of Electrical Energy

- [Advantages of electric heating; building design](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Aelectric-heating-advantages-building-design) — Utilization of Electrical Energy, chapter 5
- [Methods of electric heating](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Amethods-electric-heating) — Utilization of Electrical Energy, chapter 5

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