Housing refurbishment: Wall insulation

• Solid external walls can be insulated either internally or externally. Each method has its advantages and drawbacks.
• Cavity walls can be insulated by injecting or blowing insulation to fill the cavity.
• Performance is the key criteria in the selection of insulation materials.
• The ECT best practice U value = 0.30/m²K, but higher values are achievable

1 Internal insulation

	maintains the external appearance of the building
	quick warm-up
	reduces internal space

Design issues

• Suitability
- Confirm with the insulation manufacturer the expected U values. Check with the manufacturer the method of construction and fixing.

• Thermal Bridging
- Check detailing around window and door openings, junctions with internal partitions, separating walls and floors. At openings the insulated dry-lining should be returned into the soffit and reveals.

• Air infiltration
- seal joints between plasterboard and surrounding elements
- seal around service penetrations
- where dry lining is used, apply continuous ribbon of adhesive at the perimeter of walls, openings and service penetrations.

• Condensation
- place vapour control barrier on the warm side of the insulation
- seal joints at the junctions between lining and surrounding walls and floors
- seal around service penetrations

• Dampness in existing walls
- treat dampness before installing insulation
- if the wall has not dried out, use an independent lining method leaving at least a 25mm air gap between wall and lining. Ventilate this cavity by drilling air holes filled with mineral wool.
- when using a directly applied insulation, use a parge coat to seal the existing wall and refine the surface

• Provide timber battens for fixing kitchen units, radiators and wash basins
• With directly-fixed insulation, provide a batten to fix skirting to.
• Avoid covering cables with insulation. Cables less than 50mm from the surface of the plasterboard should be enclosed in metal conduits to avoid damage

Design strategies

Drylining fixed directly to external wall

• If the surface is uneven, the wall should be given a parge coat to refine the surface.

Insulation materials: Cellular glass, Mineral wool slab, Expanded polystyrene, Extruded polystyrene, Phenolic foarm, Polyisocyanurate (PIR), Polyurethane (PUR). (insulation can be part of a plasterboard laminate) (see also: • Insulation products and • Insulation materials compared)

Free-standing studwork with infill insulation

• Suitable for where the existing wall has a history of dampness
• Suitable for where the existing wall is uneven or bowed and where space is not at a premium

Insulation materials: Cellular glass, Mineral wool slab, Expanded polystyrene, Phenolic foarm, Polyisocyanurate (PIR), Polyurethane (PUR). (see also: • Insulation products and • Insulation materials compared)

2 External insulation

+/-	changes the appearance of the building
	retains internal thermal mass
	protects the existing walls from weathering
	provides minimum inconvenience to residents
	may require planning permission
	complications might be caused by existing external features

Design issues

• Suitability
- Confirm with the insulation manufacturer the expected U values. Check with the manufacturer the method of construction and fixing.

• Cladding system track record.
- The system selected should be tried and tested.
- The system should have third party technical endorsement.
- A list of proven systems is available from the Insulated Render and Cladding Association.
- Work should be carried out by a specialist installer

• Thermal Bridging
- Cladding should be returned into the reveals of window and door openings.
- It’s often convenient to renew windows at the same time, so as to accommodate the thickness of the cladding returns.

• Render on insulation is subject to temperature fluctuations
- reinforce render with mesh
- movement joints at max 5m centres
- use light colour finish to minimise solar gain
- use a render containing a polymer and/or reinforcement fibres

Design strategies

Insulation board and render

Insulation materials: cellulose slab, cellular glass, composite wood wool board, wood fibre board, cork, mineral wool slab, phenolic foam, Polyisocyanurate (PIR), Polyurethane (PUR), expanded polystyrene. (see also: • Insulation products and • Insulation materials compared)
Render: limecrete, mineral render, glaster, proprietary renders

Rainscreen

Insulation materials: cellulose slab, cellular glass, composite wood wool board, wood fibre board, cork, mineral wool slab, phenolic foam, Polyisocyanurate (PIR), Polyurethane (PUR), expanded polystyrene (see also: • Insulation products and • Insulation materials compared)
Cladding: wood, tiles, slate, board and polymer-based render, proprietary cladding systems

Insulating render

Insulation render: hempLime, proprietary renders (see also: • Insulation products and • Insulation materials compared)

3 Cavity wall insulation

• Check wall ties

Insulation materials: Blown mineral wool, Injected polyurethane foam, full-fill cavity (see also: • Insulation products and • Insulation materials compared)

Downloads

• Practical refurbishment of solid-walled houses, Energy Saving Trust, 2006
• Energy efficient refurbishment of existing housing CE83, Energy Saving Trust, 2004
• Refurbishing dwellings - a summary of best practice CE189, Energy Saving Trust
• Thermal Improvement of Existing Dwellings, Clarke et al, University of Strathclyde, 2005

Publications

Building Research Establishment (BRE)

• Thermal Insulation: Avoiding Risks, C.Stirling, BRE Press, 2001
• Installing Thermal Insulation, BRE Press, 2006

Standards

British Standards Institute (BSI)
• A list of applicable British Standards (.doc)

Further information

• Insulation materials compared
• The Insulated Render and Cladding Association (INCA)
• National Insulation Association
• British Urethane Foam Contractors Association

Products and materials

• Insulation products

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