BER and TER are calculated according to the national
calculation methodology (NCM). The NCM calculates the
annual energy use for a proposed building and compares it to
the energy use of a comparable ‘notional’ building in terms of
the whole building CO2 emission rate. It takes
into account of the:
•Heat loss due to temperature difference
between the internal and external environments;
•Solar heating and shading;
•Heat loss due to mass migration (air
leakage and moisture transfer);
•Daylighting;
•Artificial lighting, hot water services,
heating and cooling plant, ventilation etc.
Both calculations
for the proposed and the ‘notional’ building make use of standard
sets of data for different activity areas and call on common databases
of construction and service elements.
The notional building is a building with the
same shape, geometry and usage as the proposed building that
complies with ADL 2002, with carbon emission rate Cnotional
.
The target carbon emission rate is calculated
for the notional building taking into account an energy improvement
factor and the concession of using low and zero carbon emission
fuel.
TER = Cnotioal x (1 - improvement factor)
x (1 - LZC benchmark)
ADL-2A 2006 gives the energy improvement factor and the
LZC benchmark for different types of buildings as follows;
Servicing strategy
Improvement factor
LZC
benchmark
TER
Heated and naturally ventilated
(includes buildings with low levels of heating)
15%
10%
0.765 Cnotional
Heated and mechanically ventilated
20%
10%
0.72 Cnotional
Air conditioned
20%
10%
0.75 Cnotional
Calculation software
The whole building carbon emission rate shall
be calculated using certified software. The software enables
you to test the proposed building for compliance with ADL 2006
by any of the two approved routes:
•Simplified Building Energy Method
(SBEM);
•iSBEM for non-domestic buildings;
•SAP 2005 for dwelling buildings;
•Approved calculation methodology;
•IES 'Virtual Environment' software,
version 5.5;
•EDSL TAS Version 9.0.9.
Worst performance limit
ADL 2006 also sets out a limit for the worst
performance of building elements.
For new dwelling buildings:
Element
Area-weighted dwelling
average U-value
[W/m2K]
Worst individual element
U-value
[W/m2K]
Wall
0.35
0.70
Floor
0.25
0.70
Roof
0.25
0.35
Windows, roof windows & rooflights
2.2
3.3
Doors
2.2
3.0
For existing dwelling buildings:
Element
Area-weighted dwelling
average U-value
[W/m2K]
Worst individual element
U-value
[W/m2K]
Extensions
Renovations
Wall
0.30
0.30
Floor
0.22
0.22
Roof
0.16 on ceiling
0.20 on pitch
0.16 on ceiling
0.20 on pitch
Windows, roof windows & rooflights
1.8, or
BFRC Band D
2.0, or
BFRC Band E
Glazed doors
2.2
2.2
For non-dwelling buildings:
Element
Area-weighted average
U-value
[W/m2K]
Worst individual element
U-value
[W/m2K]
Wall
0.35
0.70
Floor
0.25
0.70
Roof
0.25
0.35
Windows
2.2
3.3
Personnel doors
2.2
3.0
High usage doors
6.0
6.0
Vehicle access doors
1.5
4.0
Area allowance
In order to limit solar overheating,
ADL 2006 also sets out allowable areas of openings.
Building type
Windows and doors as
a % of exposed wall
Rooflights as
a % of roof
Residential buildings
30
20
Places of assembly, offices
and shops
40
20
Industrial and storage buildings
15
20
Mandatory air leakage requirement
ADL 2006 requires that the air leakage rate shall be no greater than
10 m3/h/m2@ 50 Pa. The actual air leakage
rate should not be greater than the result achieved during testing.
A whole building test shall be carried
out by an accredited testing organisation (currently Taylor Woodrow
Engineering and BSRIA).
•
The Building Regulations ADL-2A 2006 requires that
all buildings with a gross floor area greater than 500 m
2 should be tested;
•
There is a Statue Law making it an offence for a
Building Control Officer to sign off a building without an air
leakage test certificate;
•
Buildings with floor area less than 500 m2
should either:
•
Be tested to show that the air leakage rate assumed
in the energy modelling has been achieved;
•
Be modelled with an air leakage rate of 15 m
3 /(h/m2). (Clearly this is disadvantageous as compensating
measures have to be taken elsewhere).
Limiting solar gain
•
Temperatures not to exceed 28oC based
on a July day;
•
Notional building uses glass with total solar energy
transmittance (g-value) of 0.65;
•
Requires consideration of:
•
Area of glass;
•Orientation;
•Glass type;
•Shading devices.
