APPROVED DOCUMENT L1A – NEW DWELLINGS

Previous methods of showing compliance such as the Elemental Method and Target U-value Method have been omitted. Instead, there is now only one approach to show compliance with the energy efficiency requirements, and this addresses 5 criteria;
a)
CO2 emissions
b)
Building fabric and services performance
c)
Limit risk of summer over-heating
d)
Construction quality control to ensure insulation and air-tightness proposed are actually achieved
e)
User information


CO2 Emissions
a)
The Target Energy Rating (TER) for a notional building must be calculated initially at the design stage, which will indicate the acceptable CO2 emissions for the dwelling. This can be calculated using SAP 2005.
b)
When the dwelling has been completed, the actual Dwelling Energy Rating (DER) as constructed must be calculated using the same method, to prove it does not exceed the TER.
It is strongly recommended that a preliminary DER is also calculated at the design stage, to give an indication as to whether it will comply on completion. Building Control Bodies can ask for this. If this is not done, there is a real danger that the completed dwelling may not be satisfactory, and extensive remedial works may then be required
Producing an overall Carbon emissions result in this way enables the CO2 emissions saving as a result of fitting solar panels etc. to be traded off against lower standards of fabric insulation or increased glazing, increasing design flexibility.

Limits on Design Flexibility – Min. Standards Exist for the Following;
a)
average u – values
b)
limiting u-values
c)
air permeability
d)
Heating / boilers
e)
Insulation of pipework
f)
Mechanical ventilation standards
g)
Mechanical cooling
h)
Lighting internal / external (low energy)


Limiting Solar Gains in Summer
Generally checked through SAP calculation, but could affect design.


Quality of Construction and Commisioning
a)
Continuity of insulation must be ensured
b)
Adopt design details and prove standard of workmanship satisfactory
c)
Developer must demonstrate that an appropriate system of site inspection is in place – e.g. checklists
d)
Air pressure testing is now required. Number of tests required depends upon system of monitoring workmanship. For small developments (up to 2 dwellings) no pressure testing required if increased air permeability allowed for in calculating DER
e)
Commissioning of heating/ hot water systems required. Notices to be provided to Building Control


Providing Information
Operating and maintenance information and instructions must be left with owner.



Page last updated on: 20/09/2010