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Description
Cement-based wall render incorporating insulation material.
Unit cost of installation
£3500 - £4000
Bulk cost of installation
Data not available.
Indicative cost and carbon saving
| £/yr saving
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kgC/yr saving
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| from
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to
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from
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to
|
|
|
| 110
|
370
|
345
|
850
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The above data assume a resulting U-value for the wall of 0.8 W/m2K.
Maintenance
Will require similar maintenance to normal render systems
Lifetime
Data is not available. The system relies on a good bond between render and substrate. Thus lifetime will depend on quality of workmanship and proper preparation.
Technical suitability
Some materials are BBA certificated as both external wall insulation systems and internal damp-proofing treatments. Thermal performance isn't as good as more conventional external wall insulation for same thickness. Detailing around windows and at eaves must be designed and implemented with care to prevent water ingress - it may be difficult to fully insulate reveals if windows are not being replaced.. Rainwater goods and other items fixed to external walls should be removed before installing the insulation and re-fixed afterwards. Care should be taken not to block air bricks, bridge damp proof courses, cover the weather drip on windows sills or block eaves ventilation. It is normally necessary to extend sills. It should not be installed on walls with rising damp without first curing the dampness problem. Substrate needs to be sound and level.
Because the insulation is applied externally the thermal mass of the walls will absorb heat from the dwelling leading to a more even temperature over a complete heating cycle, although the response time of the heating system will be lower than for lightweight structures.
If the external walls are basically sound then internal wall insulation may be a more cost-effective option.
Non-technical constraints
External insulation on terraced housing (or on one of a pair of semi-detached) can be visually obtrusive if the whole row of houses is not to be treated. In some cases planning permission may be needed. Need to check whether buildings insurance (fire) is affected.
Potential concerns with fuel poor
No specific issues.
Ancillary benefits
Potential to improve wall condition, appearance and reduce damp penetration and condensation. Reducing mould growth can have a beneficial impact on occupants' health. Occupants do not need to move out during the installation process. Since the insulation is applied externally the floor area of dwelling is not reduced.
Trigger points for work
Repairs to external walls (N.B. Building Regulations Approval is required in England & Wales whenever any thermal element is renovated, and a U-value of 0.35W/m2K would normally be required. However a lesser standard may be acceptable if it is not technically or functionally possible to achieve this U-value).
Technical Guidance Available
» CE118/GPG 293 'External insulation systems for walls of dwellings'
» BR262 'Thermal insulation: avoiding risks' BRE, 2002
» CE184 - Practical refurbishment of solid-walled houses
» BBA and BRE Certification certificates
» Insulated Render and Cladding Association - 01428 654011 - http://www.inca-ltd.org.uk
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