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Building Regulations Part L2 2010

Building Regulations Part L2 2010

The Building Regulations for England, Wales and Scotland have been revised and came into force in October 2010. These regulations present a major step change in how the energy use of buildings is determined as the Government moves towards their aspiration for zero carbon buildings.

Part L covers the building regulations in England and Wales and in Scotland this covered by Technical Handbook, Section 6 Energy.

The regulations distinguish between new build and existing properties, as well as between dwellings and non-domestic buildings. Part L is divided into four sections:

The main area of interest for metal cladding systems is the non-domestic sector and a brief summary of the changes to these building regulations is provided below.

England and Wales ADL2A: New buildings other than dwellings

A fundamental change in Part L 2010 for non-domestic buildings is in the target-setting process. The new process recognises that it is easier and more cost effective to make improvements in some building types than in others. The aim for a 25% reduction in CO2 emissions from new non-domestic buildings is achieved on aggregate across the new-build stock rather than for each individual building. Some building types will be required to achieve a bigger improvement than 25%, whilst others will need to achieve less.

The Target Emission Rate (TER) will still be generated through the National Calculation Methodology (NCM) using SBEM, but is no longer based on a 2002 notional building; instead the TER is based on a 2010 notional building aligned with the aggregate approach.

The notional building will either have 40% vertical glazing or 12% roof lights, but not both, with the allocation being driven by the planning-use class.

The limiting U-values for non-domestic buildings have not changed; these are shown below along side the figures used within the 2010 notational building.

Element

AD-L2A 2010 back stop value

2010 Notional
Building value

Roofs U-value (integral insulation)

0.25

0.18

Walls U-value

0.35

0.26

Floors U-value

0.25

0.22

Roof lights

Max 20% area

12% area

U-value

2.2

1.80

Building air permeability

10.0

5.0

The notational building also uses improved efficiencies for lighting and heating services, which will be essential for compliance. This notational blueprint is a good start for design, however, there is scope for design flexibility, and Panels and Profiles technical engineers are on hand to advise on the effects of changes to any element.

The Building Regulations now require the TER and Design Emission Rates (DER) calculations to be submitted to building control at the design stage as well as at completion. This means that on-site or last minute changes to the specification will be very difficult to justify, and could lead to non-compliance.

A revised procedure is now in place to limit the effects of solar gain, whether or not a building has air conditioning at the time of design. Architects should be aware that even where a design achieves Part L approval in a naturally ventilated building, this does not automatically mean that internal environmental temperatures will be satisfactory.

Guidance on avoiding thermal bridging at construction joints has been revised, and the option to adopt accredited construction details has been introduced. The AD-L2A, includes penalty additions to Ψ values where they are not subject to evaluation under competent persons schemes, however, no such schemes currently exist, therefore designers and contractors should use Panels and Profiles figures which have been designed using finite element analysis and will need to apply a penalty of 25% for using these. If other details or generic details as outlined in IP 1/06 are used there will be a 50% penalty, but early indications are that these penalties will have a relatively small impact on the overall design.

Finally, the requirement for a building logbook will be reinforced, despite low levels of current compliance. We can expect building control bodies to come under pressure to ensure the enforcement of this requirement, so allowance should be made for this. The recommendation in Approved Document L2A is that CIBSE TM 31 (building log books) is followed and it also recommends that the input files used in calculations should be retained.

Shell or fit out buildings

Guidance on shell and core development has also been revised, and it will now be necessary to specify at the design stage how the shell and services will meet the requirements. It won't be possible to simply design the shell to base levels and leave it to the fit-out contractor to install highly efficient services to compensate. On practical completion, it will be necessary to provide as-built calculations with the fit-out areas conditioned to the previously assumed

temperatures. A predicted Energy Performance Certificate (EPC) rating is also required to show what level of performance is possible. However, there is no requirement for an EPC to be formally lodged.

England and Wales ADL2B: Existing buildings other than dwellings

The requirements for existing non-domestic buildings are essentially the same, but with some amendments to the standards for controlled fittings, retained thermal elements and (as shown in the table below) new thermal elements.

Element

(a) Standard for new thermal elements

(b) Standard for replacement thermal elements

(c) Limiting U-value for existing elements not worse than

Walls

0.28

0.30

0.70

Roofs (with integral insulation)

0.18

0.18/0.20*

0.35

Scotland Non-domestic Handbook, Section 6 - Energy

The Scottish approach is basically the same approach as we are currently using; i.e. a 2002 notional building with a percentage improvement (in Part L this is called the flat approach).

However the backstop values have been improved, and the percentage improvement over 2006 levels is a flat 30% (this equates to approximately 50% improvement over the 2002 notational building). This is likely to mean greater emphasis on improvements to all areas, especially on hotels, offices and commercial type buildings.

The following tables include the standard package of construction performance measures for the notional building and backstop values:

Element

AD-L2A 2010 back stop value

2002 Notional
Building value

Roofs U-value (integral insulation)

0.20

0.25

Walls U-value

0.27

0.30

Floors U-value

0.22

0.25

Roof lights U-value

2.0

2.2

No backstop value is set for air permeability. However, it is recommended that buildings be designed to achieve a value of 10m³/m²/ph @ 50Pa or better.

Shell or fit out buildings

Where a building warrant application is made for the building shell only, air permeability should not exceed 7m³/m²/ph at 50Pa and testing should be carried out both at completion of the shell and again when the fit-out is completed. Also the following maximum U-values apply to the envelope.

Element

Max U-value for shell or fit out buildings

Roofs U-value (integral insulation)

0.15

Walls U-value

0.23

Floors U-value

0.20

Roof lights U-value

1.6


Refurbishment or Extensions to the building envelope

Where the insulation envelope of a building is extended, or the building envelope is upgraded, either by removing the existing construction and reinstating with new, or retaining the existing internal layer and building in an improvement, the performance of the new building fabric should be designed in accordance with the following table:

Element

(a) Area-weighted average U-value for all elements of the same type (W/m2K)

(b) Individual element
U-value (W/m2K)

Roofs U-value (integral insulation)

0.15

0.7

Walls U-value

0.25

0.7

Floors U-value

0.20

0.35

Roof lights U-value

1.6

3.3

The maximum windows, doors and roof-light areas are shown below:

Building Type

Windows and doors as % of the area of
exposed wall

Roof-lights as %
of area of roof

Residential buildings, offices, shops and buildings for entertainment and assembly purposes

40

20

Industrial and storage buildings

15

20

The U-values for the elements involved in the building work may be varied provided that the area-weighted U-value of all the elements in the extension is no greater than that of a 'notional' extension. The notional extension should be the same size and shape as one designed to the elemental U-values in column (a) of the table above, when the area of openings, in the walls (excluding separating walls where it is considered that zero heat loss occurs) and roof of the 'notional' building are as the percentages above.

If you require any technical support or guidance on the new Building Regulations Part L2 2010 please contact Panels and Profiles technical department on 0845 30 88 330.

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