NOTES

The following notes are provided by Energy Check Ltd. They are a personal interpretation, and highlight main points to the regulations:

• nursing homes, and in particular, student accommodation and similar, are now not considered as dwellings
• heated common areas to flats, and commercial or retail space are to be considered under L2A (non-dwellings)
• workshops, offices, studios etc. that have direct access to the living accommodation, where both are contained within the same thermal envelope (and could revert back to living space), and where the living accommodation occupies a considerable proportion of the total building area, are all dealt with as dwellings under L1A
• SAP energy rating continues to be required, in order to provide the dwelling’s Energy Performance Certificate (From April 2008). Apart from using standard designs, the output provided by new SAP software covers much of the requirements of the 5 criteria mentioned below
• the separation wall(s) and door(s) between the dwelling and an unheated conservatory or garage, need to be similarly insulated/draughtproofed as the rest of the perimeter walling.
• the Target emissions (TER) and the calculated Dwelling emissions (DER) have to be based on a specified target air permeability. This could be 10 m³/(h.m²) at 50 Pascal (just remember the 10 bit!), which is a reasonable assumption for air loss. It is feasible to reduce this to 3 to 4 using a high standard of construction. On small residential developments (NOT MORE THAN 2 DWELLINGS), you have the option of a pressure test at completion, if the particular builder has not had a similar dwelling type tested in the preceding 12 months, OR the dwelling needs to be designed to 15 m³/(h.m²). In practice this could mean more insulation, wider walls etc. which would probably have a cost implication beyond the cost of a pressure test
• it is now more important to properly specify windows (see window rating), external doors, loft access hatches (with associated insulation, sealing and fixing), recessed lighting units that intrude into unheated loft areas), external meter enclosures
• heating and hot water insulation requirements and controls are not specified in Part L1. In line with policy, a separate document (the Domestic Heating Compliance Guide) is referred to
• domestic air conditioning is now referred to
• low energy internal lighting is more adequately described. For specifications, it is easiest to refer to the particular compact fluorescent lamps as 4 pin CFLs. External lighting should be mentioned in the specification,
• lintels, external meter boxes and other discrete thermal bridges must now be considered.
• the thermal capacity of the building materials is now considered in respect to possible seasonal overheating. Orientation of windows is now more important.

   The Five Criteria for Compliance:

1. The target carbon dioxide emission rate (TER) is a minimum energy performance requirement for a notional dwelling of the same size and shape as the actual, calculated using SAP based on insulation, heating, hot water, ventilation and internal lighting.  The actual dwelling carbon dioxide emission rate (DER) is the actual emission rate, calculated in the same way, and compared against the TER. To comply, it must be equal or better.
   
   In essence, compliance is judged by comparing actual CO2 emissions against those of a notional house.
    
2. Limits on design flexibility take into account fabric heat loss. The performance of the building fabric and the heating, hot water and fixed lighting systems to be not worse than set limits
    
3. The dwelling has appropriate passive control measures to limit solar gains (to eliminate the need for air conditioners).
    
4. A check that the performance of the dwelling, as built, is consistent with the DER
    
5. Certification that the necessary provisions for energy efficient operation of the dwelling are put in place