Internal Solid Wall Insulation
The insulation of solid walls is considerably more difficult than the insulation of cavity walls. Due to the lower potential savings and higher cost of undertaking the work it is best to incorporate the insulation of solid walls into major internal repair of the interior of the dwelling. Furthermore the work, although it can be done whilst the occupants remain in residence, is substantially more disruptive than the process of insulating cavity walls.
Internal wall insulation is also known as insulated dry lining and consists of a layer of insulating material installed behind a layer of plasterboard. It is applied from the inside and necessitates the removal of all fittings affixed to the walls - radiators, skirting boards, architraves etc.
Insulated dry lining can take the form of a composite 'thermal board' or a built up system using insulation behind timber battens fixed behind conventional plasterboard. For both systems the surface of the wall must be carefully prepared and all cracked or damaged plaster must be either repaired or removed. Bare brickwork or blockwork should be pointed with mortar to eliminate air paths to the exterior.
Made of plasterboard bonded to an insulating material.
Incorporate a vapour control layer to prevent water vapour passing through the board and condensing on the cold masonry behind.
Boards are available incorporating a variety of insulants, e.g. polystyrene, polyurethane and mineral wool.
Usually 25mm - 50mm thick, with the thicker boards being the most insulating.
Should be fixed to the wall using a continuous ribbon of plaster or adhesive, and not individual 'dabs' of plaster, unless the wall is particularly uneven.
2. Built up systems
Conventional mineral wool Insulation is placed between vertical timber battens fixed to the wall
A polythene sheet is fixed over the insulation and battens beneath the plasterboards and acts as the vapour control layer.
Joint edges and services (electrical cables and wiring) which penetrate the polythene sheet must be thoroughly sealed using tape to exclude water vapour and subsequent condensation formation behind the lining.
Whichever system is installed it is very important to ensure that moisture cannot penetrate behind the plasterboard as condensation and dampness will result.
Additional insulation will be required around the sills and reveals of openings and adjacent to where internal masonry partitions meet external walls in order to prevent thermal bridging.
The installation of internal wall insulation will result in a slight reduction of the floor area of the rooms concerned.
Rooms will heat up more quickly after insulation and hence this form of insulation is particularly suited to dwellings that are heated intermittently, such as in the morning and evening.
Special fixings must be used to affix pictures and small items to plasterboard lining.
Heavy items must be fixed through the dry-lining into the masonry wall behind the insulation.
'Energy Efficiency Best Practice in Housing 'publications provide information and advice on all aspects of energy efficiency in domestic dwellings. These can be obtained free of charge by calling 0845 120 7799 or visit the Energy Saving Trust website (external link).
The publications concerned with the internal insulation of solid walls are:
- GPG138: Internal Wall Insulation in Existing Housing
- GPG297: Refurbishment site guidance for solid walled houses - walls