June 2010 - NHBC Home

Standards
Extra
Regulation Changes
It is now a requirement to submit
Target CO 2
emission rates (TER),
Dwelling/Building CO 2
emission rates
(DER/BER) for the building, and a list of
specifications used in the calculations
to the Building Control Body before
works start on site.
Main Changes
So what are the implications of the
recommendations contained within
Part L 2010, and how will they impact
on the design and construction phases?
1. Air permeability andpressure
testing
Essentially the amount of on-site
testing is likely to at least double.
Either three units or 50% of each
dwelling type should be tested on each
site, whichever is the lesser. Blocks of
flats are treated as separate sites, even
if there are multiple blocks within the
same development.
The specific dwellings to make up the
test sample should be selected by the
Building Control Body in consultation
with the appointed pressure testing
body. Early appointment of the testing
body could be beneficial here.
The other significant change is the
relevant information to include in
the DER calculation. Where pressure
tested, this specific figure should be
used. For non-tested dwellings, the
DER figure should be the average
test results achieved for the same
dwelling type +2.0m 3 /(h.m 2 ) at 50Pa.
This in basic terms means that design
air permeability will be nearer 8.0m 3 /
(h.m 2 ) to achieve compliance with the
maximum value of 10.0.
2. Requirement to submit information
With the introduction of Regulation
20D, it is now a requirement to
submit TER and DER information
and calculations in full, including the
specifications used to achieve the
design CO 2
emissions, to the Building
Control Body prior to works starting
on site.
The current requirement to submit
DER achieved alongside the TER
information, together with information
pertaining to changes in specifications
to reflect the as-built dwelling, within
five days of completion remains.
An EPC is also required for all new
dwellings and non-domestic buildings.
3. Improved limiting U-values
New limiting U-values have been
introduced for the building fabric,
and are as follows:
External Walls 0.3 W/m 2 .K
Roofs 0.2 W/m 2 .K
Party Walls 0.2 W/m 2 .K
Floors 0.25 W/m 2 .K
Windows 2.0 W/m 2 .K
A significant change for Part L 2010 is
the notional dwelling used for the TER
assumes a party wall U-value of 0.0
W/m 2 .K. The above limiting U-values
require inclusion of party walls in the
overall fabric insulation calculation.
In reality cavity party walls will
require some insulation, although
of course all current robust details
for acoustic performance show clear
cavities to prevent sound transfer. The
implications here are currently being
reviewed, and we should be able to
provide more detailed guidance in
due course.
4. SAP 2009
Thermal bridges – effective U-values
should now be based on the length
of each junction and the relevant psi
values from SAP 2009. An alternative is
to use a relevant approved government
accredited construction detail scheme,
although details of such schemes are
not yet available, so initially SAP 2009
will be the option together with on-site
checks during construction.
Energy efficient light fittings – at
least 75% of light fittings must be low
energy, determined by the Domestic
Building Services Compliance Guide.
Providing more than 75% low energy
lighting provision will help toward the
DER calculation.
Secondary heating – the default penalty
has been removed and is now based on
the actual secondary heating provided,
with the exception of dwellings with a
chimney but no appliance installed, in
which case there is no change from the
current default penalty.
A preview of SAP 2009 can be viewed
from www.nesltd.co.uk website.
5. Shell and Core developments
There is clearer guidance on the
construction of shell and core units,
whether stand alone or part of mixed
use developments. The developer
should show by the design stage
TER/BER calculations how the building
shell could meet energy efficiency
requirements.
Where certain systems are not
installed, the BER will have to assume
efficiencies for those services that
will be installed as part of the first
fit out work, and these figures and
assumptions in full must be provided to
the Building Control Body before the
works start.
Part F 2010 – Ventilation
Introduction
Part F 2010 includes significant
revisions to align with the changes
made in Part L, ensuring minimum
energy efficiency levels for all
ventilation systems.
The use of trickle ventilation looks
set to become more difficult, with
additional guidance published for
dwellings with design stage air
permeability tighter than 5.0m 3 /(h.m 2 ),
meaning approximately 50% more
background ventilation is required for
dwellings with intermittent or passive
stack ventilation systems.
This could prompt designers and
builders to move towards continuous
ventilation systems, which are better
performing in SAP 2009, as well as
simpler to standardise. Continuous
ventilation systems do not require
trickle vents either, which could be a
significant advantage.
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