Walls: Insulating drylined walls

The thermal performance of walls may be improved by installing an insulated dry-lining system with Ballytherm Insulation behind plasterboard. This method is well suited to refurbishment projects where existing walls have to be upgraded. The properties of Ballytherm Insulation match those required for this application: its low thermal conductivity minimises the thickness of insulation required, thus limiting the loss of internal volume whilst giving the necessary thermal performance.

The Ballytherm boards may be installed directly behind the plasterboard and restrained by the plasterboard fixings. Alternatively, the boards may be restrained by timber battens fixed through to the wall, with the plasterboard secured to the battens to leave voids between the insulation and the plasterboard.

The reflective surface of the boards reduce radiation heat loss across the air spaces and further improve the thermal performance of the wall.
The thickness of Ballytherm Insulation required to meet regulations may be determined from table 9.

Design guidance
To minimise thermal bridging at window and door reveals insulation should be installed along the face of the reveal and butted to the window frame (figure 22). If space constraints preclude the use of battens, the plasterboard should be fixed to the wall through the Ballytherm Insulation boards.

Thermal bridges can also occur where interior walls meet external walls; one solution is to extend the insulation for at least a metre along both faces of the internal wall, although to avoid projections in the wall it may be appropriate to continue the insulation to an internal corner (figure 23).
In intermediate floors, insulation should be placed between the inner surface of wall and the joist which runs next to it (figure 24).

Walls must be prepared for installation: projections such as skirting boards, architraves and copings should be removed to give a smooth surface, uneven walls may need to be rendered; service fixtures such as sockets and switches should be removed to be
re-fitted later. Existing finishes with a high vapour resistance, such as vinyl wallpaper or gloss paint should be removed to avoid problems with condensation.

The cavities formed by the battens may be used for service runs to reduce penetrations through the insulation: where existing services are taken through the insulation the penetrations should be sealed. Lightweight fittings may be fixed to the plasterboard, but fixings for heavier fittings should be taken back to the masonry.

Additional battens should be used to support heavy horizontal items.

Sitework
Installation sequence - with battens

1. Prepare the wall surfaces, removing projections and high vapour resistance finishes.
2. Fit Ballytherm boards against the wall. Fix in place with timber battens.
   
3. Tape board joints with metalised tape.
   
4. Fix plasterboard to battens and skim.
   
5. Refix skirtings and surrounds. Re-install services.

Points to watch

• Run services in the batten space behind the plasterboard. Where services run behind the insulation, chase into the wall, not the Ballytherm boards.
• Fix Ballytherm boards to window
  and door reveals to avoid thermal bridging.