Thermal Regulations - England, Wales & Northern Ireland
Part L1A & F1
Thermal Regulations for new dwellings (England and Wales)
2006
A tightening of the requirements for energy conservation has
inevitably resulted in a greater level of sophistication in the
method of showing compliance. The EPBD requires a calculation
method that adopts a whole building approach to energy performance.
The 2006 version of SAP has been developed for Approved Document
L1A that meets this requirement. The SAP worksheet and
specification can be downloaded from www.bre.co.uk/sap2005
In addition, there is greater emphasis on ensuring that the
building construction meets the standards assumed at the design
stage and that the heating and hot water systems are correctly
commissioned.
How to comply
The five criteria set out below describe the process the
designer and builder must go through to show compliance.
Absolute criteria
The 2005 version of SAP calculates the dwelling’s energy
performance in terms of CO2 emissions per m2
per year for heating, hot water, ventilation and lighting.
The SAP calculation tool allows the designer a high degree of
flexibility in deciding how to achieve the required energy target.
However, the Approved Document does set certain limits.
These include:
- Limiting U-values (see Table 4)
- A limit of 10 m3/m2/h at 50 Pa for air
permeability
- Central heating boilers must be class A or B (at least 86%
efficient)
- Energy efficient lighting in at least a quarter of light
fittings
1.
Calculating the CO2 emissions for the proposed
building1
The predicted rate of carbon dioxide emissions from the dwelling
(the Dwelling Emission Rate (DER)) should not be greater than the
Target Emission Rate (TER).
How to comply
Using the Standard Assessment Procedure (SAP2), the
CO2 emission rate is calculated for a notional dwelling
of the same size and shape as the proposed dwelling using a fixed
set of criteria for the fabric heat loss building services and fuel
choice.
The resulting ‘notional’ CO2 emission rate is
equivalent to a gas heated dwelling insulated to Part L standards
for 2002. Table 2 lists the U-values used to calculate the
CO2 emission rate for the notional building.
The Target CO2 Emission Rate (TER) is arrived at by
reducing the notional CO2 emission rate by 20% and
making an allowance for any change in the main heating fuel, using
the ‘fuel factor’ (see Table 1). The SAP calculation is repeated,
but this time inserting the proposed U-values, building services,
fuels and low or zero carbon energy sources for the proposed
building. This produces the Dwelling Emission Rate (DER). If the
DER of the proposed building is less than the TER, the first
criteria has been achieved.
Table 1 - Fuel
Factor
| Heating Fuel |
Fuel Factor |
| Mains Gas |
1.00 |
| LPG |
1.10 |
| Oil |
1.17 |
| Grid electricity (for direct acting, storage and electric heat
pumps) |
1.47 |
| Solid mineral fuel1 |
1.28 |
| Renewable energy, including bio-fuels such as wood
pellets1 |
1.00 |
| Solid multi-fuel1 |
1.00 |
|
|
Table 2 - U-Values used in notional
building
| Element |
U-value
(W/m2K)
|
| Wall |
0.35 |
| Floor |
0.25 |
| Roof |
0.16 |
| Glazed openings and doors |
2.00 |
|
1 For Northern Ireland only –
The non-lighting element of the TER is increased by a 1.14
multiplier for fuels other than mains gas, renewable energy and
solid multi-fuels.
2 Note that the SAP calculation
submitted for building control approval must be carried out by a
suitably qualified person. The energy certificate must be produced
by someone who is authorised to issue SAP Certificates.
2. Design limits
Show that the thermal performance of the building fabric and the
heating, hot water and lighting systems are within the design
limits in the Approved Document.
How to comply
Approved Document L1A lists limiting U-values for the building
fabric. These are set out in Table 3. The average weighted U-value
for any of the elements listed should not be exceeded. Similarly,
no individual area of an element should exceed the values in column
(b) in Table 3.
The Approved Document also sets out the limiting criteria
for:
- air permeability
- heating and hot water systems
- insulation of pipes, ducts and vessels
- mechanical ventilation and cooling
- lighting
Table 3 - Limiting U-values
(W/M2K)
| Individual Element |
(a) Area weighted
dwelling average |
(b) Worst Element |
| Wall |
0.35 |
0.70 |
| Floor |
0.25 |
0.70 |
| Roof |
0.25 |
0.35 |
| Glazed openings and doors |
2.20 |
3.30 |
3. Limiting solar gains in summer
Provision should be made to prevent high internal temperatures
due to excessive solar gains.
How to comply
Appendix P of SAP 2005 enables designers to calculate if there
is a high risk that solar gains will result in high internal
temperatures. The risk can be reduced by changing the window size
and orientation, or introducing shading devices.
4. Quality of construction and commissioning of building
services
Demonstrate that the quality of construction has been achieved
by adopting Accredited Details and undertaking an air pressure test
to confirm the specified design air permeability has been achieved.
Provide a notice declaring that the building services have been
inspected, tested and commissioned and are in accordance with the
proposed building design.
How to comply
Suitable site inspection and checking is required to confirm the
satisfactory installation of the insulation to minimise thermal
bridging, eg meeting the Accredited Details where adopted in the
design.
An air permeability test must be carried out to show that the
design air permeability standard has been achieved. Air pressure
testing is required to be carried out to an approved procedure by
an ATTMA member or similar accredited tester.
The DER should be recalculated to reflect any changes between
the design assumptions and actual performance of the
construction.
The heating and hot water systems should be commissioned and a
notice issued by a competent person3 at the local
authority to confirm this has taken place.
3 Where an Energy Performance
Certificate is being issued to certify a building’s energy
performance, this must be carried out by an energy assessor who is
a registered competent person. Factors which enable individuals to
train and qualify as accredited energy assessors include: competent
use of SAP methodology conventions and calculations, training on
relevant units of the National Occupational Standards,
qualification certificates, advisory reports and relevant
qualifications relating to the design, construction or energy
assessment of buildings.
5. Providing information
Provide operating and maintenance instructions to enable the
building and its services to be operated in an energy efficient
manner.
How to comply
The owner of the building should be provided with a set of
simple operating and maintenance instructions explaining how to use
the installed heating and hot water system to achieve economy in
use.
