| Introduction
- Note the regulations changed in October 2010 for more information
see here |
| On 31st October 2001, the government published
the new regulations, with the regulations coming into force on the 1st
April 2002.
|
There are two documents
- L1 Conservation of fuel and power in
dwellings.
- L2 Conservation of fuel and power in
buildings other than dwellings
|
|
The regulations refer to several documents which are
either new and unpublished or are being revised. |
In particular:
- BRE IP 17/01 Assessing the effects of thermal bridging at junctions
and around
- MCRMA Technical Note 14: Guidance for the design of metal cladding
and roofing to comply with Approved Document L 2002 Edition:
- BRE BR 262, 2002 Edition Thermal insulation: avoiding risks
- Robust construction details for dwellings and similar buildings, TSO,
2001.
- Conventions for U-value calculations
- U-values for light steel-frame
construction
- BRE IP5/98 Metal Cladding
assessing the thermal performance. This has been replaced by IP10/02 Metal Cladding
assessing the thermal performance of built-up systems which use 'Z'
spacers
|
| The requirements which relate to our industry
are: |
|
L1(a)
|
Reasonable provision shall be made for the conservation of
fuel and power in dwellings by
- Limiting the heat loss through the fabric of the building
|
| |
To meet the requirement
- Limit the heat loss through the roof, wall, floor, windows and doors
etc by suitable means of insulation
- Limit unnecessary ventilation heat loss by providing building fabric
which is reasonably airtight
|
| L2 (a) |
Reasonable provision shall be made for the conservation of fuel and
power in buildings or parts of buildings other than dwellings by
- Limiting the heat losses and gains through the fabric of the
building
|
| |
To meet the requirement
- limit the heat loss through the roof, wall, floor, windows and doors
etc by suitable means of insulation
- Limit the heat gains in summer
- Limit heat losses (and gains where relevant) through unnecessary air
permeation by providing building fabric which is reasonably airtight.
|
|
| L1 Dwellings |
| Methods for demonstrating reasonable provision for limiting heat loss
through the building fabric: |
- Elemental method
- Target U-value method
- Carbon Index method.
|
| The Elemental Method is suitable for alterations and extension work,
and for new-build work when it is desired to minimise calculations. |
| The Target U-value Method allows
greater flexibility than the Elemental Method in selecting the areas of
windows, doors and rooflights, and the insulation levels of individual
elements in the building envelope, taking into account the efficiency of
the heating system. |
| The aim of the Carbon Index Method is to provide more
flexibility in the design of new dwellings whilst achieving similar
overall performance to that obtained by following the Elemental Method.
The Carbon Index adopted in this method is defined in the Government’s Standard
Assessment Procedure for Energy Rating of Dwellings. |
| Requirements for Elemental Method |
| U-value thermal performances |
| Element |
U-values (W/m2 K) |
| Pitched roof with insulation between rafters |
0.2 |
| Pitched roof with insulation between joists |
0.16 |
| Flat roof |
0.25 |
| Wall |
0.35 |
| Windows, doors and rooflights, glazing in metal frames |
2.2 |
| Windows, doors and rooflights, glazing in wood or PVC
frames |
2.0 |
|
| Areas for windows, doors and rooflights
|
| Should
not exceed 25% of the total floor area. |
| Other Requirements |
| Limiting thermal bridging at junctions
and around openings |
| Adopt the recommendations in the report on
robust standard details, which gives examples of design details and
constructional practices that can deliver the required performances. |
| Air Leakage |
| Guidance on some ways of reducing infiltration
is given in the report on robust standard details. |
| Alternative the dwelling may be pressure
tested, with a result not exceeding 10m3/h/m2 at an applied pressure difference of 50 pascals. |
| L2 Buildings Other Than Dwellings |
| Methods for demonstrating reasonable provision for limiting heat loss
through the building fabric: |
- Elemental Method
- Whole-Building Method
- Carbon Emissions Calculation Method
|
| The elemental method considers the performance
of each aspect of the building and sets out minimum performance criteria
of each element, including the building envelope, heating system, lighting
and air conditioning etc. |
| The other two methods relate to the Carbon
Performance Rating (CPR) of the building as a whole, the Whole Building
Method being suitable for offices, schools and hospitals, and the Carbon Emissions
Calculation Method for any building type. |
| Requirements for Elemental Method |
| U-value thermal performances |
| Element |
U-values (W/m2 K) |
| Pitched roof with insulation between rafters |
0.20 |
| Pitched roof with insulation between joists |
0.16 |
| Flat roof or roof with integral insulation |
0.25 |
| Walls |
0.35 |
| Windows, roof windows and doors, glazing in metal
frames |
2.2 |
| Windows, roof windows and doors, glazing in wood or
PVC frames |
2.0 |
| Rooflights |
2.2 |
| Vehicle access and similar large doors |
0.7 |
|
| Areas for windows, doors and rooflights |
| Building type |
Windows & doors as %
of the internal area of exposed wall |
Rooflights as % of area
of roof |
| Residential buildings |
30 |
20 |
| Places of assembly, offices and shops |
40 |
20 |
| Industrial and storage buildings |
15 |
20 |
|
| Other Requirements |
| Continuity of Insulation |
| Submit evidence, that appropriate design
details and building techniques have been specified, and that the work has
been carried out in ways that can be expected to achieve reasonable
conformity with the specifications. (See BRE Information Paper IP 17/0128
and the MRCMA Technical Report No 1429 ) |
| Alternatively carry out an infra-red
thermographic survey which shows that the insulation is reasonably
continuous over the whole visible envelope. |
| Building Air Leakage Standards |
| For buildings less than 1,000 m2 gross floor
area, submit evidence that
appropriate design details and building techniques, have been specified,
and that the work has been carried out in ways that can be expected to
achieve reasonable conformity with the specifications.
|
| OR |
| For buildings of any size, carry out of air leakage
tests.
|
| From 1st October 2003, reasonable provision would be test results
showing air permeability not greater than 10 m3 /h/m 2 ,
with an applied pressure difference of 50 Pascals. |
| Documents |
| BRE - Conventions for U-value calculations
- BRE |
| This is a
guide to the use of the relevant U-value calculation procedures to
comply with the Approved Documents L1 and L2 (2002) as given in British
Standards and other documents, and it will help those who commission and
carry out such calculations. It indicates which calculation methods are
appropriate for different construction types, and provides additional
information and data relevant to typical UK constructions. This guidance
is concerned with the U-values of building materials and building
elements - walls, roofs, floors, basements, windows and doors - and also
covers various issues that commonly arise when undertaking U-value
calculations. |
| There is also a software package to accompany this
document, for more information click here |
| BRE U-values for light steel-frame construction |
| This Digest gives a method for assessing U-values of light
steel-frame constructions. The method has been validated using the
procedures in BS EN ISO 10211-1 and enables U-values to be calculated by
means of a simplified method. It is similar to the one given in BS EN ISO
6946 but with some important differences. It can easily be incorporated
into software tools used by designers, builders and enforcers of the
Building Regulations wishing to calculate U-values of light steel-frame
constructions. The method was developed jointly by BRE and The Steel
Construction Institute. This Digest supports the 2002 editions of Approved
Documents L1 and L2 for the Conservation of Fuel and Power. It is
addressed to designers and others concerned with energy efficiency in
buildings and assumes that they are familiar with the procedure for
calculating U-values given in BS EN ISO 6946. |
| BRE - IP10/02 Metal Cladding
assessing the thermal performance of built-up systems which use 'Z'
spacers |
| This
Information Paper describes a method for determining the thermal
performance of insulated double-skin metal roof and wall systems used in
the UK that incorporate "Z" spacers. It can be used to demonstrate
compliance with the 2002 editions of the building regulations. The
method takes account of the thermal bridging caused by the metal
connecting paths between inner liner and outer sheet. Built-up systems
using rail and brackets are dealt with in Metal cladding: U-value
calculation Assessing thermal performance of built-up metal roof
and wall cladding systems using rail & bracket spacers published by the
Steel Construction Institute. Other metal cladding systems should be
assessed by numerical modelling of the specific construction type. This
paper replaces IP 5/98 |
| In addition to the above two publications from
The Steel Construction Institute: |
P311 The design of twin-skin
metal cladding
How to meet the new requirements of Part L of the Building Regulations
(2002) |
P312 Metal Cladding: U-value calculations
Assessing thermal performance of built-up metal roof and wall cladding
systems using rail and bracket spacers. |
