Insulation of buildings

About 1500 million people live in cold climates where some heating in buildings is required. In most countries the energy demand of space heating in buildings is far greater than it need be if the buildings were better insulated (Figure 11.7).

Table 11.1 provides as an example details of two houses, showing that the provision of insulation in the roof, the walls and the windows can easily lead to the energy requirement for space heating being more than halved (from 5.8 kW to 2.65 kW). The cost of the insulation is small and is quickly recovered through the lower energy cost.

If a system for circulating air through the house is also installed, so that incoming air can exchange heat with outgoing air, the total heating requirement is further reduced. In this case it is worthwhile to add more insulation to reduce the heating requirement still further.

Figure 11.7 An image of Aberdeen (Scotland, UK) from the air taken in the infrared in the winter. Red buildings are warm as a result of poor insulation. Blue buildings are cool showing they are well insulated. Red buildings include some of the older buildings near the city centre but also some much more recent buildings in the outskirts.

Figure 11.7 An image of Aberdeen (Scotland, UK) from the air taken in the infrared in the winter. Red buildings are warm as a result of poor insulation. Blue buildings are cool showing they are well insulated. Red buildings include some of the older buildings near the city centre but also some much more recent buildings in the outskirts.

Table 11.1 Two assumptions (one poorly insulated, and one moderately well insulated) regarding construction of a detached, two-storey house with ground floor of size 8 m x 8 m, and the accompanying heat losses (U-values express the heat conduction of different components in watts per square metre per °C)

Poorly insulated

Moderately well insulated

Walls (150 m2 total area)

Brick + cavity + block: U-value 0.7

Brick + cavity + block with insulation in cavity of 75 mm thickness: U-value 0.3

Windows (12 m2 total area)

Uninsulated: U-value 2.0 Uninsulated: U-value 1.0 Single glazing: U-value 5.7

Covered with insulation of thickness 150 mm: U-value 0.2 Includes insulation of thickness 50 mm: U-value 0.3 Double glazing with low emissivity coating: U-value 2.0

Heat losses (in kW) with 10 °C temperature difference from inside to outside

k Windows r 0.7

T

T

Floor 0.7

^ Floor 0.2

Total heat loss (kW)

Add heat (in kW) needed for air changes (1.5 per hour)

Total heating required (kW)

2.65

(fossil-fuel) Developments (ZED).21 The box illustrates a recent development in the UK along these lines.

Efficiency increases bringing cost savings sound very good in principle. In practice, however, it is frequently found that much of the energy and cost saving fails to materialise because of the increased comfort or convenience that comes from increased energy use - hence an increase in energy demand. Energy efficiency measures need therefore to be associated with adequate public education that explains the need for overall energy reductions.

Alongside the increases in energy efficiency in buildings and appliances, there need to be moves to carbon-free sources of energy supply to the buildings sector. These will be addressed in later sections.

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