Objectives of Part L
ADL 2006 sets out to make buildings more energy efficient, with an aim to reduce carbon production by one million tons per year. To satisfy EPBD requirements, new buildings energy performance standards must be 20% - 28 higher than the ADL 2002 notional building, based on the whole building Target CO2 Emission Rate (TER).

New document structure
ADL 2006 is significantly different from previous Approved Documents, in both layout and content. The new document is split into four parts reflecting the specialisation in the construction market:
L1A: New Dwelling
L1B: Work On Existing Dwellings
L2A: New Building - Other Than Dwellings
L2B: Work On Existing buildings - Other Than Dwellings

Methods of compliance
The three previous methods of compliance detailed in ADL1 and ADL2 : 2002 can no longer be used. The new ADL offers only one method of compliance, based on the whole building energy performance approach. All new buildings MUST now achieve a minimum CO2 emissions rate (TER) based on the following methodologies:
ADL1A - SAP 2005 (SAP worksheet and specification can be downloaded from www.bre.co.uk/sap2005)
ADL2A - NCM /SBEM (Simplified Building Energy Model). Further information can be downloaded from www.ncm.bre.co.uk

Design considerations
To ensure compliance , a number of factors will need to be addressed at the design stage.
Airtightness of the building
Artificial lighting (internal & external)
Building fabric U-values
Building type and configuration
Glazing areas and orientation
Heating and hot water
Method of ventilation
Thermal bridging details

Elemental U-Values
For L1A and L2A the elemental U-value approach can no longer be used as a stand alone method of compliance, other than for setting minimum acceptable performance standards for the building envelope.

New dwellings - Demonstrating compliance Compliance with L1A is
demonstrated by meeting five criteria:
1. The Dwelling Emission Rate (DER) is no greater than the TER.
2. The performance of the as built dwelling is consistent with the DER.
3. Provisions are put in place to ensure the energy efficiency of the dwelling.
4. The buildings fabric and fixed services perform no worse than set design limits.
5. Appropriate passive control measures are put in place to limit the effect of solar gain on the dwelling.

Achieving the TER
Using SAP, calculate the CO2 emission rate of a notional building (Table. 2) based on the same size and shape as the proposed dwelling, using a fixed set of criteria for the fabric heat loss, fuel choice and building services. The resulting CO2 emissions rate is then equivalent to a gas heated dwelling insulated to ADL 2002 standards. The TER is arrived by reducing the notional buildings CO2 emission rate by 20% and making an allowance for any changes in the main heating fuel using the fuel factor (Table. 3).

The SAP calculation is then repeated but this time inserting the proposed fuels, building services, U-values and low or zero carbon energy sources for the proposed dwelling. This produces the Dwelling Carbon Rate (DER). If the DER is less than the TER the first set of criteria has been achieved.

Limit on design flexibility
It must be shown that the thermal performance of the dwelling fabric, lighting systems, heating and hot water systems are within the design limits.

ADL1A gives limiting U-values for the dwelling's fabric (Table. 1) The area weighed average U-value for of any element listed in column a should not be exceeded. To ensure the TER is met, the performance of most of the elements will need to be significantly higher than those shown. In addition, to minimise the risk of condensation, no single element should exceed the values listed in column b e.g recessed external services box.

Limiting solar gain in summer
To prevent high internal temperatures due to solar gain, designers should use Appendix P of SAP 2005 to calculate the level of risk. It should be noted that the use of air conditioners in dwellings is discouraged by the Government.

Quality of construction and commissioning
The building insulation envelope should be constructed in such a way as to avoid where possible thermal bridging. Recognised design details should be adopted, and to ensure quality of construction an air pressure test should be carried out by an accredited tester.

The heating and hot water systems should be signed off by a competent person. To determine the DER, a calculation should be made based on the dwelling's actual construction, taking into account any changes made and the air permeability test .

Providing information
To ensure the building operates in an efficient manner, the owner of the building should be provided with information about the building, the fixed services installed, and their maintenance. This information will eventually form part of the Home Information Pack.

New Building (Other than Dwellings)
Demonstrating compliance
Demonstrating compliance with ADL2A is similar to ADL1A but using the SBEM methodology rather than SAP. New build non-domestic ADL2A energy standards have been improved by 28% compared to ADL Part 2: 2002 standards. Compliance with AL1A is demonstrated by meeting five criteria:
1. The Building Emission Rate (BER) is no greater than the TER.
2. The performance of the as built dwelling is consistent with the BER.
3. Provisions are put in place to ensure the energy efficiency of the building.
4. The building's fabric and fixed services perform no worse than set design limits.
5. Appropriate passive control measures are put in place to limit the effect of solar gain on the building.

Air permeability and pressure testing
All new buildings, other than dwellings require an air pressure test to be carried out by an accredited tester, with the exception of:
Buildings with a floor area less than 500m2.
Factory made modular buildings.
Large complex buildings.
Refer to ALD2A for further information.

The heating and hot water systems should be signed off by a competent person. To determine the DER a calculation should be made based on the dwellings actual construction, taking into account any changes made and the air permeability test.

How Can TETRiS Help?
TETRiS can provide typical U-values as low as 0.16W/m2K, giving flexibility in designs of other elements in order to achieve the required Target Emissions Rating (TER). The TETRiS system also ensures design compliance by embracing the Robust Construction Details, BRE report: Thermal insulation: Avoiding risks 2002 edition and information paper IP01/06 : Assessing the effects of thermal bridging at junctions and around openings in the external elements of buildings, BRE 2006.

Introduction | Tetris & The Environment | Thermal Performance | How Does It Work? | Structural Floor Finish | Advantages | Accreditation | Typical Construction | Construction Details