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- SAP
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DSJ Planning & Design |
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SAP Energy Ratings TER/DER |
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BUILDING REGULATIONS (Guidance Notes) New Methods of Compliance TER & DER Main Changes The main difference to
come out of the new regulations is the way compliance is calculated. 1.
Firstly the
standard SAP information is input into the programme and a TER (Target Carbon
Dioxide Emission Rate) is calculated for a notional building of the same
size, configuration and orientation as the actual property. This figure
cannot be altered and would be different for any alternative design and size. 2.
Secondly the
DER (Dwelling Carbon Dioxide Emission Rate) is calculated and this is
affected by the components used and various other designs as detailed below.
Identical buildings with the same TER could have a different DER depending on
their orientation. Whichever way you design your dwelling the DER must never
be greater than the TER. 3.
For Flats and
Terraced houses an average weighted TER and DER can be calculated but for the
final certificate each flat or dwelling still has to be individually
calculated in order to obtain the EPC’s. Main Factors to bear in Mind 1.
The 2010 guide
values have altered slightly, changes are in red: ·
Wall 0.28W/m2K ·
Roof (flat
ceilings) 0.16W/m2K ·
Roof (sloping
ceilings) 0.18W/m2K ·
Flat
Roof 0.18W/m2K ·
Floor 0.22W/m2K ·
Openings
(windows) 1.60W/m2K ·
Openings
(doors) 1.80W/m2K ·
Opening area
25% total floor area ·
Boiler Gas
86% efficient ·
Pressure
Test 8m2/(h.m2)@50Pa 2.
To obtain a
satisfactory result with regards to the new Code 3 requirement you will need
to incorporate accredited construction details to limit thermal bridging and
air leakage from the dwelling. The current details are (Robust Details TSO 2001
– Limiting Thermal Bridging and air leakage Robust Construction Details for
new Dwellings) but these are soon to be revised and a new system will be put
in place where you have to purchase the details for your project. These will
then be filled in by your contactor and handed to the Building officer who
will provide you with a certificate on completion. 3.
It is best to
keep Conservatories thermally separated from the main dwelling especially if
there are glazed roofs, mainly because solar over heating could cause the
dwelling to fail compliance (see below). Despite this in certain circumstances
a conservatory can be beneficial in providing solar gain but this can be
ascertained by the SAP calculation. 4.
Solar over
heating was added to the calculations in 2006 and the dwelling will not
comply if the temperature of the building is likely to exceed 23.5 deg C
during hot weather. Factors which will affect this are: ·
Size, shape
and orientation of openings ·
External
shading, overhangs, balconies etc ·
Internal
blinds, curtains etc ·
Ventilation ·
Thermal Mass
(see 7 below) ·
Mean summer
temperature for region For the last item I will need to
know the location of the dwelling so that I can pick the exact
region in which it is situated. 5.
Care must be
taken to eliminate Thermal Bridging which is now included within the
calculations. Again if you use accredited details (as stated above) this will
produce a lower DER but you can still use the default figure of 0.15 which
would increase the DER and also prevent you achieving Code 3 compliance. 6.
You need to
be careful with ventilation especially (whole house) ventilation which can
affect the DER. It is best to consult Part F of the Building Regulations for
more details as it is too complicated an issue for me to go into the details
here. 7.
The Thermal
Mass of the building mainly affects the ‘Solar over heating’. One thing to
bear in mind is that a more solid building does not heat up as fast as a
lighter structure but retains heat for longer. 8.
Low Energy
Lighting now has more effect on the calculations, you now have to install 3
per 4 fixed fittings and the DER/CO2 figures will decrease further the more
you install. 9.
Heating – The main boiler and the fuel are still critical
and you can now install two main heating boilers. The secondary heating can
also be critical and this will benefit the calculations if a wood-burning
stove can be integrated with the main heating to reduce the use of fossil
fuels. If you are thinking of adding secondary heating, details are needed at
the outset. 10. If no other renewable heating source is used on
the project it may be necessary to include Solar Water Heating or Photo
Voltaic (PV) Technology to further reduce the DER and CO2 figures and obtain
a pass. Conclusion There are certain elements that should be agreed between the
Architect and the developer/client prior to the drawings being finalised.
These are not absolutely vital but would make the process of obtaining a
satisfactory DER less complicated. ·
The type and
make of preferred insulation block ·
The make of
preferred floor insulation ·
The make of
preferred wall insulation ·
The make of
preferred roof insulation ·
A preferred
boiler manufacturer would also be helpful The above assist in the
design and reduce the final calculations because different types of
insulation have different thermal properties and if the developer/contractor
changes the item this could cause the dwelling to fail when the final ‘as
built’ DER is calculated which would then cause serious problems. A developer/contractor
with a good workforce and excellent site practices should produce good
pressure test results and this would then provide scope for insulation and
other details to be refined on future projects. NB Please note that the above is
just my summary of the new regulations and is just to assist you in providing
me with the necessary information that I will require in order to produce the
TER and DER values for your project. It will still be necessary for you to
consult the new Building Regulations Part L1a, L1b, F & G to confirm
items as circumstances change from project to project. |
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