| On the 1st
October 2010, the latest version of Part L Conservation of Fuel and
Power of the Building Regulation came into effect. |
| Part L2 deals
with building other than dwellings, there are two parts, part A for new
buildings and Part B for existing buildings. |
| Part A -
New Buildings |
|
The main principle is that the energy
performance of the building shall not exceed that of a notional building
of the same size and shape as the actual building. Unlike the 2002
regulation there are no specified U values for the roofing and cladding
systems. |
|
The form of measurement of energy performance
of the notional building is the target carbon dioxide Emission Rate (TER).
The TER is calculated using approved software, one being the Simplified
Building Energy Model (SBEM). |
In terms of
roofing and cladding the information required for the model is
- U values of the systems
- Linear thermal transmission value Ψ
(psi value) of junctions
- Air permeability of the building
|
| The values for
the U values for the notional building are specified in the National
Calculation Methodology (NCM) modelling guide (for buildings other than
dwellings in England and Wales) 2010 Edition. |
| Element |
U-values (W/m2 K) |
| Roof |
0.18 |
| Walls |
0.26 |
| Windows, roof windows and
rooflights |
1.8 |
| Vehicle access and similar
large doors |
1.5 |
| Pedestrian doors |
2.2 |
|
| The air
permeability of the Notional building must be 5m³/h per m² envelope at
50 Pa. |
|
Values for the actual building the Building
carbon dioxide Emission Rate (BER) needs to be calculated. The U
values should be specified by the design team but must not be greater
than. |
| Element |
U-values (W/m2 K) |
| Roof |
0.25 |
| Walls |
0.35 |
| Windows, roof windows,
rooflights, curtain walling and pedestrian doors |
2.2 |
| Vehicle access and similar
large doors |
1.5 |
| Roof ventilators |
3.5 |
|
| The air
permeability of the actual building must not exceed 10m³/h per m²
envelope at 50 Pa. |
| Part B -
Existing Buildings |
| Renovation of
Thermal Elements |
| Where more
than 50% of an individual roof is to be re-roofed then the new roof
shall comply with the regulations. The U values that should be
achieved are: |
| Element |
U-values (W/m2 K) |
| Pitched roof - insulation
at ceiling level |
0.16 |
| Pitched roof - insulation
at rafter level |
0.18 |
| Flat roof or roof with
integral insulation |
0.18 |
| Walls |
0.3 |
|
| However the
Regulation does say that these values should only be achieved where it
is technically functionally and economically feasible. |
| Where it is
not feasible, then the the element should be upgraded to the best
standard that is technically and functionally feasible and which
meets a simply payback criterion of 15 years or less. |
