National Building Regulation Standards for the insulation of buildings were first introduced in 1965, and at that time were applicable only to dwellings. Their objective was part of an overall aim to maintain minimum standards of health and safety within buildings. Since then, the insulation standards have been progressively improved and their scope extended to all buildings. Simultaneously, the objective of this part of the Building Regulations has expanded from a concern for health and safety within individual buildings to include the conservation of fuel and power at a national level. Originally, the trend towards conservation of fuel and power was a defensive reaction to instability in the price and availability of oil on the world market, as well as being a contribution to environmental welfare. More recently, steadily increasing pollution of the atmosphere by various gases has become a major international concern. In this context, the most relevant gas is carbon dioxide, and for several reasons:

• Increases in carbon dioxide levels in the atmosphere lead to global warming and climate change

• Carbon dioxide levels in the atmosphere are on a rising trend

• Carbon dioxide is the main end product of the consumption of fuel for energy

• As buildings are, in total, among the largest consumers of fuel and energy, they are also one of the largest contributors to the increase in atmospheric carbon dioxide and hence to global warming and climate change.

The average global temperature is the result of a balance between the shortwave solar radiation penetrating the earth's atmosphere and the outgoing thermal long-wave radiation. Several gases in the earth's atmosphere, most notably carbon dioxide, absorb the outgoing radiation more efficiently than the incoming radiation, hence maintaining the average temperature at or about its customary level. The connection between atmospheric carbon dioxide and global temperature can be seen in Fig. 1.1, which is a simplified graph of the changes which are believed to have occurred naturally over time. This shows global temperature closely following carbon dioxide levels in a repeating cyclic fluctuation. If this fluctuation were to continue, carbon dioxide and temperature levels would, at the present time, be expected to be near peak values and be beginning to fall. However, both are continuing to rise to levels that are much higher than ever before. Although previous peaks have been around 280 ppm

400000 200000 0

Number of years before the present time

Fig. 1.1 Carbon dioxide concentration and global temperature.

400000 200000 0

Number of years before the present time

Fig. 1.1 Carbon dioxide concentration and global temperature.

(parts per million), by the year 2000 the global C02 concentration was on a sharply rising trend, and had reached 360 ppm. In the wake of this rise, global temperature has been found to be rising at a rate, which is expected to continue, of about 1° Celsius every 40 years. The consequences of allowing this rise to continue are thought to be unacceptable, and so action to reduce or even prevent it is considered necessary.

Clearly, controlling carbon dioxide levels and global warming is an international problem, which requires action on several fronts. As one part of its contribution to that process, the UK government has made the relevant part of the Building Regulations more stringent, and has emphasised that the objective of conserving fuel and power is to reduce carbon emissions into the atmosphere. This has been done by using carbon emissions as one of the principal criteria by which the performance of a building is judged. This in turn has had a substantial impact on the structure and detail of the Regulations. For carbon emission targets to be met, all aspects of a building's design and operation that might affect those emissions must be considered and are therefore included in the regulatory framework. An alternative method of rating the energy performance of a building is to convert its on-site consumption to an equivalent amount of primary energy. The primary energy figure is a measure of the total amount by which a natural resource has been depleted for every unit of useable energy delivered to an end user. The primary energy, therefore, takes account of all the extra energy used in producing the fuel and delivering it to the building in a form that is ready for consumption. Some of the literature relevant to Part L of the Building Regulations refers to primary energy rather than carbon emissions. In practice, the two measures are performing the same function, and the carbon emission factors given in Table 3.5 for various fuels are similar, apart from a conversion factor, to primary energy ratios.

As far as the Building Regulations are concerned, requirements for the conservation of fuel and power are dealt with by Part L of Schedule 1, and there are two Approved Documents providing practical guidance for meeting the requirements. The first, Approved Document L1 (AD L1), is applicable to dwellings, and the second, Approved Document L2 (AD L2), is applicable to all buildings other than dwellings. The two documents are separate publications and are substantially different. However, there are some common elements between them and these areas of commonality are listed in Table 1.1. All other material differs between the two documents, even though there is some similarity in the wording in places. It is therefore important to maintain the distinction between the regulations and requirements of L1 and L2 when applying them to a specific building project. Consequently, in this book parts L1 and L2 are treated separately. However, to avoid undue repetition, the common material in 'Use of Guidance' and in 'Introduction to the Provisions' (L1 paragraphs 0.5 to 0.16; L2 paragraphs 0.9 to 0.20) is considered first, then L1 and L2 are described separately in Chapters 2 and 3. The common material in Appendices A, B, C and D is presented in Chapters 4, 5, 6 and 7, followed by the remaining Appendices of L1 and L2 in Chapters 10, 11, 12 and 13. The requirement to achieve an acceptable standard of airtightness for the external

Table 1.1 Material common to LI and L2.


Paragraph in LI

Paragraph in L2


Use of Guidance

Identical except for 'Mixed Use Development' in L2

Technical risk



Thermal conductivity and transmittance

0.6 to 0.9

0.10 to 0.13

U-value reference tables



Calculation of U-values

0.11 to 0.13

0.15 to 0.17

Roof window



Basis for calculating areas



Air permeability



Limiting thermal bridging at junctions and around openings

1.30 to 1.32

1.90 to 1.11

Identical except for some additional references in L2

Appendix A: Tables of U-values

The whole Appendix

The whole Appendix

Appendix B: Calculating U-values

The whole Appendix

The whole Appendix

Appendix C: U-values of ground floors

The whole Appendix

The whole Appendix

Appendix D: Determining U-values for glazing

The whole Appendix

The whole Appendix

The principle is the same but the examples differ

fabric of a building, and the possible need to test for air leakage, is a new development and is discussed in Chapter 14.

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