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Technical Advice Note Version 1.0 (August 2013) Page 1 of 17
Technical Advice Note:
Retrofit External Wall Insulation (EWI)
Applied to Dwellings
August 2013
Technical Advice Note Version 1.0 (August 2013) Page 2 of 17
Technical Advice Note –
Retrofit External Wall Insulation (EWI) Applied to Dwellings
1. Introduction
Background
In a typical house, between 33% and 45% of the building's heat is lost through the walls. The
addition of external wall insulation (EWI)1 is therefore an effective means of both increasing
thermal efficiency and reducing fuel bills, with expected annual savings of between £250 and
£550 for a three-bedroom semi-detached house2. EWI is a particularly useful measure for
those dwellings classed as 'hard-to-treat', typically older dwellings of solid wall construction,
meaning that they are unsuitable for cavity wall insulation. Coventry has a large number of such
properties, including over 45,000 in the city's private housing sector alone2.
Until recently, the uptake of EWI had been very limited in Coventry, primarily due to the
relatively high costs involved. However, mainly as a result of its inclusion in the utility company-
funded Community Energy Saving Programme (CESP), which finished at the end of 2012, and
its replacement, the Energy Company Obligation (ECO), EWI is becoming increasingly common.
CESP and ECO set legally-binding targets requiring utility companies to invest in insulation and
heating improvements, particularly in deprived areas. By December 2012, some 2,900 housing
association dwellings and 300 private dwellings in the city had been treated with EWI, and it is
predicted that this number will increase dramatically over the coming years.
Given the above, a need has emerged for clear guidance on requirements - covering planning,
building control and highways - relating to the application of external wall insulation to domestic
properties in the city, which this document has been produced to fulfil. It is directed at any
individual or organisation seeking information on requirements for EWI, including Green Deal
providers, housing associations, and private householders and landlords considering adding
external insulation to their properties.
1 EWI comprises an insulation layer fixed to the outside of an external wall using a combination of mechanical fixings
and adhesive, and a protective render or cladding finish. It is suitable for solid wall, non-traditional and cavity wall properties and offers several advantages, in addition to the energy efficiency improvements referred to above, as follows:
Work is done externally so there is very little disruption and no internal redecoration is required afterwards;
No living space is lost as a result of the insulation being applied;
The system will provide additional protection to the property and, in some cases, the appearance of the building is improved;
Condensation risk is managed to the outside of the home and, if the insulation is continuous, thermal bridging is minimised; and,
Little maintenance is required.
2 Opinion Research Services (2012). Private Sector Stock Condition Survey: Coventry City Council. Report of
Findings. Draft 22nd
March 2013. Swansea: Opinion Research Services
Technical Advice Note Version 1.0 (August 2013) Page 3 of 17
Guidance scope, aims and overview of content
This guidance covers the application of external wall insulation (EWI) to existing dwellings in
Coventry. It aims to:
a) explain the current Planning, Building Control and Highways requirements and provide
guidance on how they are applied in the Coventry context; and,
b) give examples of how these are applied in practice.
The remainder of this document is divided into six sections, as follows:
Section 2 covers the current planning requirements applicable to external wall insulation
Section 3 gives an overview of relevant building control requirements
Section 4 describes requirements relating to highways
Section 5 gives some examples of how this guidance would be applied in the case of some
typical house types in Coventry
Section 6 covers some of the questions frequently asked about EWI
Section 7 shows the contact details of relevant departments within the Council to whom any
relevant questions should be addressed.
Technical Advice Note Version 1.0 (August 2013) Page 4 of 17
2. Planning requirements
Is planning permission required for external wall insulation?
External wall insulation is classed as permitted development, which means that planning
permission is not required, but this applies only if the materials used are of a similar
appearance to those used in the existing building. In any case, permission is generally only
needed where the EWI is to be applied to the front facades of a building. Full details are given
in The Town and Country Planning (General Permitted Development) (Amendment) (No.2)
(England) Order 2008 and associated technical guidance3, which states
"Development is not permitted [i.e. planning permission is required] if:
(d) the enlarged part of the dwellinghouse would extend beyond a wall which –
(i) fronts a highway, and
(ii) forms either the principal elevation1 or a side elevation of the original
dwellinghouse."
Clarification specifically of the status of EWI with respect to the above is provided in the
technical guidance, as follows:
"The installation of solid wall insulation constitutes an improvement rather than an
enlargement or extension to the dwellinghouse and is not caught by the provisions of d(i)
and d(ii)."
However, a number of conditions are stipulated which must be complied with in order for this to
apply, including that:
"The materials used in any exterior work…shall be of a similar appearance to those used
in the construction of the exterior of the existing dwellinghouse.
The condition above is intended to ensure that any works to enlarge, alter or improve a house result in an appearance that minimises visual impact and is sympathetic to existing development. This means that the materials used should be of similar visual appearance to those in the existing house, but does not mean that they need to be the same materials. For example, the external walls of an extension should be constructed of materials that provide a similar visual appearance – for example in terms of colour and style of brick used – to the materials used in existing house walls."
3 Town and Country Planning (General Permitted Development) (Amendment) (No.2) (England) Order 2008. SI
2008/2362, London: TSO / Department for Communities and Local Government (2013). Permitted development for
householders. Technical guidance. London: DCLG.
Technical Advice Note Version 1.0 (August 2013) Page 5 of 17
In practice this means that, where EWI with a standard smooth or lightly textured render
finish is being proposed:
for a redbrick building with no existing render, planning permission is required;
a redbrick building which is partially rendered, on the other hand, is classed as
permitted development, i.e. planning permission is not required;
in the case of a fully rendered building, planning permission is not required; and,
for a pebbledashed or wet dashed building, permission is likely to be required, as the
addition of EWI render would be expected to result in a change of texture and appearance.
However, in any given case whether planning permission is needed will depend on the
particular circumstances, so if you are uncertain please check with Planning (contact details
given in Section 7).
Where a dry dash (pebbledash) or wet dash finish is proposed:
a property which is already pebbledashed or wet dashed, either fully or partially, would
not usually be expected to need planning permission, on the basis that the appearance
of the building would not be fundamentally changed; whereas
in all other cases, planning permission would normally be required. Again, if you are
unsure how to apply this guidance in your particular circumstances, please contact Planning
(see Section 7 for contact details).
Notes:
A. For some locations within the city, planning conditions have been applied in order to remove
some or all permitted development rights. Depending on which particular rights have been
removed at a given location, this may or may not affect whether planning permission is
required for EWI. The following link will take you to an interactive map showing all areas of
the city where some or all permitted development rights have been removed:
http://www.coventry.gov.uk/info/1023/planning_advice_and_guidance/1333/online_planning
_map
To see only the layer relating to permitted development rights, untick all items on the Map
Legend (left hand side of page) except the one entitled 'NPD Area'. Affected areas are
hatched in blue on the map. By single-clicking on a particular hatched area you can see
details of which permitted development rights have been removed at that location. If the
statement ‘All permitted development rights removed’ appears in the pop-up box, this means
that planning permission will always be required be required for EWI. If a different message
appears, on the other hand, you are advised to clarify with Planning whether permission is
needed before commissioning or commencing any work.
Technical Advice Note Version 1.0 (August 2013) Page 6 of 17
B. For buildings located within designated Conservation Areas (known as Article 1(5) land), the
following requirements apply:
"In the case of a dwellinghouse on Article 1(5) land, development is not permitted [that is,
planning permission is required]…if:
a) it would consist of or include the cladding of any part of the exterior of the
dwellinghouse with stone, artificial stone, pebble dash, render, timber,
plastic or tiles;
b) the enlarged part of the dwellinghouse would extend beyond a wall forming
a side elevation of the original dwellinghouse; or
c) the enlarged part of the dwellinghouse would have more than one storey
and extend beyond the rear wall of the original dwellinghouse."
This means that in practice planning permission will always be needed for houses located
within Conservation Areas.
C. In the case of Listed or Locally Listed Buildings, any proposals should always be discussed
with the Council prior to an application for planning permission being submitted. In addition
to planning permission Listed Building consent will be also be required. (This latter
requirement applies to Listed Buildings only. It does not apply to Locally Listed Buildings.)
What factors are taken into account by Planning when deciding whether to give planning
permission (where needed) for EWI?
In determining planning applications for external wall insulation, each case will always be judged
on its own individual merits, and a balance struck between good design and improving energy
efficiency of properties. The main national and planning policies to which reference will be
made are as follows:
National Planning Policy Framework4
"Local planning authorities should not refuse planning permission for buildings or
infrastructure which promote high levels of sustainability because of concerns about
incompatibility with an existing townscape, if those concerns have been mitigated by
good design (unless the concern relates to a heritage asset and the impact would cause
material harm to the asset or its setting which is not outweighed by the proposal's
economic, social and environmental benefits".
[Section 7 ('Requiring good design'), Clause 65]
"To support the move to a low carbon future, local planning authorities should…
actively support energy efficiency improvements to existing buildings".
[Section 10 ('Meeting the challenge of climate change, flooding and coastal change'),
Clause 95]
4 Communities and Local Government, 2012. National Planning Policy Framework. London: DCLG
Technical Advice Note Version 1.0 (August 2013) Page 7 of 17
The Coventry Development Plan 20015,
o Policy OS4 (Creating a More Sustainable City):
"The developing concepts and techniques of sustainability will be applied through
policies in this Plan to:
ensure the efficient use and re-use of land and buildings;
……. and
promote the good stewardship of the natural and built environment."
o Policy H4 (Residential Extensions):
"Extensions or other alterations to residential properties should respect the local
character and street-scene of the area".
o Policy BE2 (Principles of Urban Design):
"High quality urban design will be promoted by ensuring that all new development
takes into account the following design principles:
enhancing townscape and landscape character by reflecting locally distinct
patterns of development;
strengthening the continuity of street frontages and the enclosure of space by
development which clearly defines the boundaries between private and public
space; and,
…….
ensuring that developments are sustainable in terms of their design, layout and
density."
In general terms, this means:
for traditionally-built brick terraces, semi-detached and detached houses consideration
will be given to the impact on the overall character of the area and street-scene, together
with the architectural merit of the property / properties concerned. It may be deemed
necessary for traditional, characteristic or decorative design features of the property, such
as lintels, cills, dentil courses, corbelling and bay windows, to be retained or replicated as
part of the external cladding. Where such features cannot adequately be retained or
replicated it is likely that planning permission would not be granted
for properties in Conservation Areas planning permission will only be granted if it can be
clearly demonstrated that the historic character of the area will not be adversely affected.
The addition of EWI will not be permitted in cases where it is deemed to have a negative
impact on either the building itself or the conservation area as a whole
for Listed and Locally Listed Buildings planning permission is unlikely to be given for
external wall insulation applied to any elevation, owing to the significant impact it would have
on the appearance and historic fabric of the building.
5 Coventry City Council, 2001. The Coventry Development Plan 2001. The City of Coventry Unitary Development
Plan 1996-2011. Coventry: Coventry City Council
Technical Advice Note Version 1.0 (August 2013) Page 8 of 17
What information needs to be provided in support of a planning application for EWI?
When applying for planning permission for EWI, the following information needs to be
submitted:
Set of completed standard application forms
Stipulated application fee
Location plan of the application site at a scale of 1:1250, with the site outlined in red
Photograph(s), taken prior to any works commencing, of all elevations of the building
to which the application refers
Elevation drawing(s) or (a) photo image(s) clearly showing the extent of the
proposed cladding. Again, these should cover all elevations of the building to which
the application refers
Cross-section drawings to show thickness of cladding and any detailing where
specialist treatment may be required, as described in Section 2.
Applications should be made online via the Planning portal, at:
www.planningportal.gov.uk?PpApplications/genpub/en/Ecabinet .
Details of fees payable can also be found at the same location.
Note:
At the discretion of Planning, where there are a significant number of properties within the same
locality to receive EWI treatment, it may be possible to make a block application, covering a
number of different addresses. Contact Development Management (details given in Section 7)
for further details.
Technical Advice Note Version 1.0 (August 2013) Page 9 of 17
3. Building control requirements
The application of external wall insulation to an existing dwelling is covered by the requirements
of The Building Regulations 20106, on the basis that one or more thermal elements7 are being
renovated. The requirements relating to building work are given in Schedule 1 to the
regulations. For EWI, as long as the work does not constitute a material alteration8, the only
applicable section of the Schedule is L1(a)(i), which requires:
"reasonable provision for the conservation of fuel and power in buildings by:
(a) limiting heat gains and losses -
(i) through thermal elements and other parts of the building fabric"
Details of how this can be achieved in practice are given in Approved Document L1B:
Conservation of fuel and power in existing dwellings9. The main requirement is that where a
thermal element is being renovated an area-weighted U-value of 0.3W/m2K for the whole
element needs to be achieved10. However, if it can be demonstrated that this requirement
would result in a simple payback of more than 15 years, a higher, less stringent U-value may
apply. This would need to be agreed with Building Control in advance of the any works being
carried out.
External wall insulation is now covered by a number of competent persons schemes. This
means that an installer who is registered with such a scheme is permitted to self-certify their
work as being compliant with Building Regulations. Details of current competent persons
schemes and how they are authorised can be found on the GOV.uk website11. An installer who
is not a member of a scheme may still carry out external wall insulation works but must have
them certified by a building control body (either the local authority or an approved inspector). As
part of this, prior to works commencing the installer is required either give notice to the local
authority of the intention to carry out the work or deposit a full set of plans with the local
authority, as described in the Building Regulations.
Listed Buildings and dwellings in a Conservation Area need not comply with energy efficiency
requirements of Part L if to do so would unacceptably alter the character of appearance of such
buildings. (However, as explained in Section 2, in most cases planning permission would be
refused anyway for the retrofitting of EWI to these types of buildings.)
Further information about Building Control can be found at: www.coventry.gov.uk/buildingcontrol
6 Building and Buildings, England and Wales. The Building Regulations 2010. SI 2010/2214, London: TSO
7 'Thermal element' means a wall, floor or roof (but does not include windows, doors, roof windows or roof-lights)
which separates a thermally conditioned part of the building from either outside, or a part of the building which is not thermally conditioned or is conditioned to a different temperature. 8 An alteration is considered to be 'material' where the work being carried out would at any stage result in a building
or controlled service or fitting (for instance a window, drain or electrical work) either not complying where it did prior to the works being carried out or being made less compliant 9 HM Government, 2010. The Building Regulations 2010. Conservation of fuel and power. Approved Document L1B:
Conservation of fuel and power in existing dwellings. In effect from 1 October 2010. London: NBS 10
This requirement applies where the area being renovated covers at least 50% of the individual element or 25% of the whole building envelope 11
Located at: https://www.gov.uk/competent-person-scheme-current-schemes-and-how-schemes-are-authorised#current-schemes
Technical Advice Note Version 1.0 (August 2013) Page 10 of 17
Table 1 gives an overview of the Planning and Building Control requirements that are likely to
apply for external wall insulation for particular property types and locations.
Table 1: Summary of Planning and Building Regulations requirements
Dwelling type
1. No designation (i.e. columns 2, 3 and 4
do not apply)
2. Dwelling located
in Article 4
Direction area
3. Dwelling located
in Conservation
Area
4. Listed or Locally
Listed Building
Planning
permission
required?
No – but only if
materials used are
of a similar
appearance to
those used in the
existing building
Yes – all other
cases
May or may not be
required depending
on what is included
in Article 4
Direction covering
location
Yes Yes
Conditions likely
to be applied to
permission
(where relevant)
Significant
architectural
features to be
retained or
replicated as
specified
Significant
architectural
features to be
retained or
replicated as
specified
Appearance of
building to remain
unchanged
Planning
permission not
expected to be
granted due to
impact on
appearance and
historic fabric of
building
Listed Building
consent
required?
Not applicable Not applicable Not applicable Yes (for Listed
Buildings only)
Building
Regulations
apply?
Yes – Part L only Yes – Part L only Yes – Part L only Yes, if character &
appearance of
building can be
retained to an
acceptable degree
(refer to Building
Control for advice)
Building
Regulations Part
L requirements
Area-weighted U-
value of 0.3W/m2K
to be achieved on
all thermal
elements to which
EWI applied*
Area-weighted U-
value of 0.3W/m2K
to be achieved on
all thermal
elements to which
EWI applied*
Area-weighted U-
value of 0.3W/m2K
to be achieved on
all thermal
elements to which
EWI applied*
Area-weighted U-
value of 0.3W/m2K
to be achieved on
all thermal
elements to which
EWI applied*
* Note: if simple payback to achieve U-value of 0.3W/m2K would exceed 15 years, then a higher, less stringent U-
value may be agreed. Please refer to Building Control for advice.
Technical Advice Note Version 1.0 (August 2013) Page 11 of 17
4. Highways requirements
Highway encroachment
Where EWI is added to a dwelling immediately adjoining a public highway (i.e. where there is no
fore garden), Section 177 of the Highways Act 1980 applies, on the basis that the construction
will project beyond the boundary of the property into the highway or associated footway. This
means that, in theory at least, a licence to carry out the works is required. However, the Council
takes a pragmatic approach and, for standard 60mm phenolic board and 90mm expanded
polystyrene EWI systems, a licence would not usually be required, except in cases where the
width of the existing footway is less than 150mm, when the Highways department should always
be consulted (see Section 7 for contact details).
Scaffolding licences
If the work requires the erection of scaffolding and this scaffolding will extend onto a public
highway or associated footway, a scaffolding licence will be required from the Council’s
Highways department. In order to apply for a licence, the following information needs to be
provided:
Completed application form. (Blank forms are available from Highways – see Section 7
for contact details)
A copy of the scaffolding company’s public liability insurance certificate (minimum
required coverage of £5 million)
Plan(s) clearly showing where the proposed scaffolding is to be located in relation to the
building(s) to which it is applied
Stipulated licence fee.
Technical Advice Note Version 1.0 (August 2013) Page 12 of 17
5. Examples: typical Coventry house types
A. No-fines property
Description Wimpey no-fines property, constructed c.1950
Typical features None
Proposed EWI system
Wetherby Building Systems Epsicon 3 Wall insulation system –
60mm phenolic foam, glass fibre mesh embedded in scrim adhesive
and aggregate dash (pebbledash) finish on dash receiver render
Overall thickness approx 70 - 80mm.
Planning permission
required
Yes
Specific conditions
applied to permission
None
Property prior to
addition of EWI
(smooth render finish)
Property following
addition of EWI
(aggregate dash finish)
Technical Advice Note Version 1.0 (August 2013) Page 13 of 17
B. Traditionally-built terraced house – few architectural features of note
Description Mid-terraced house, constructed pre-1919
Typical features Corbelling / dentil course, plain stone lintels / cills, bay windows
Proposed EWI system
Wetherby Building Systems - 60mm phenolic foam plus WBS silicone
render system (scrim adhesive coat reinforced with glass fibre
reinforcing mesh, scrim adhesive levelling coat, silicone primer and
silicone finish)
Overall thickness approx 70mm
Planning permission
required
Yes
Specific conditions
applied to permission
Any lintel, cill and corbelling detail on the existing dwelling shall be
retained or replicated on the external elevation of the cladding hereby
permitted in accordance with the indicative details shown on the
approved elevation or sectional drawings
Typical property
without EWI
Typical property
following addition of
EWI
Technical Advice Note Version 1.0 (August 2013) Page 14 of 17
Note:
In the example above the cill had already been removed during previous works carried out at
the property and therefore replication was unnecessary in this instance. The illustration below
shows a property where the original cill detailing has been replicated using a WBS proprietary
system.
Property with EWI
applied, showing cill
and lintel replication
Cill detail drawing
(image reproduced with
permission from Wetherby
Building Systems Ltd)
Technical Advice Note Version 1.0 (August 2013) Page 15 of 17
C. Traditionally-built detached house – significant architectural features
Description Detached house constructed pre-1919
Notable features Corbelling, decorative lintels / canopy over door, checkerboard
brickwork pattern, name plaque
Proposed EWI system
Wetherby Building Systems - 60mm phenolic foam plus WBS silicone
render system (scrim adhesive coat reinforced with glass fibre
reinforcing mesh, scrim adhesive levelling coat, silicone primer and
silicone finish).
Overall thickness approx 70mm.
Planning permission
required
Yes, although unlikely to be given
Specific conditions
applied to permission
Application not made following preliminary discussions with Planning.
Proposals did not adequately maintain or replicate architectural
features – suitable solution not deemed to exist currently.
Property prior to
addition of EWI
Technical Advice Note Version 1.0 (August 2013) Page 16 of 17
6. Frequently Asked Questions
Why do I need planning permission for external wall insulation when what I'm doing will benefit
the environment by helping to combat climate change and reduce energy use?
Planning permission is required in some instances because, as explained in Section 2, not all
properties are covered by permitted development rights. However, where permission is required,
in determining the application due consideration will be given to the wider benefits of the
proposals, and a balance will be struck between the need to preserve the character of a building
and its neighbourhood, and the energy efficiency improvements / carbon dioxide emissions
reductions that will result from the work being carried out.
If my home is in a Conservation Area will I automatically be refused planning permission?
No, your application will be assessed on its individual merits. However, the need to retain
Conservation Area status is paramount, and will usually mean that planning permission will not
be granted for the addition of EWI unless it can be clearly demonstrated that the appearance of
the building will not be changed. It is therefore recommended that in these instances you seek
advice prior to submitting a planning application.
Are there any restrictions to the type of EWI finish that may be applied?
There are a number of different EWI finishes available on the market, including render (the most
commonly used type), brick slips, tiles and decorative boards. Whilst there are no particular
restrictions on the type of finish that may be applied, Planning will, when determining planning
applications for EWI, take into account the overall appearance of the building, which should be
preserved as far as possible, as described in Section 2 above.
If the proposals do not meet the requirements of Part L of the Building Regulations due to the
payback period exceeding 15 years, will Building Control approval still be granted?
If you consider that a U-value of 0.3W/m2K cannot be achieved without the simple payback
exceeding 15 years, it may be possible to agree a higher U-value target with Building Control.
However, it is important that you seek advice from Building Control prior to the commencement
of works.
Technical Advice Note Version 1.0 (August 2013) Page 17 of 17
7. Contacts
For enquiries about planning permission / planning applications:
Development Management (Planning)
Civic Centre 4 – Floor 3
Much Park Street
Coventry CV1 2PY
Telephone: 024 7683 1212
Email: planning@coventry.gov.uk
For enquiries about Building Regulations:
Building Control
Civic Centre 4 – Floor 3
Much Park Street
Coventry CV1 2PY
Telephone: 024 7683 2057
Email: buildingcontrol@coventry.gov.uk
For enquiries about Conservation Areas and Listed Buildings:
Conservation and Archaeology Officer
Civic Centre 4 – Floor 3
Much Park Street
Coventry CV1 2PY
Telephone: 024 7683 1271
Email: christopher.patrick@coventry.gov.uk
For enquiries about Green Deal & ECO:
Domestic Energy Efficiency Manager
Civic Centre 4 – Floor 1
Much Park Street
Coventry CV1 2PY
Telephone: 024 7683 1356
Email: david.shiner@coventry.gov.uk
For enquiries about highways:
Assistant Engineer – Traffic Management
Civic Centre 4 – Floor 8
Much Park Street
Coventry CV1 2PY
Telephone: 024 7683 2035
Email: stewart.adams@coventry.gov.uk
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