Solid Wall Insulation


  • Average house could save £475 a year
  • More comfortable home
  • Lower carbon emissions
  • Can be installed internally or externally
  • Unlikely to qualify outright for Green Deal finance but may qualify for a top-up grant to make up the difference – See CERO

Insulating outside walls reduces heat loss in winter and achieves heat gain in summer.

There are several methods of insulating solid walls. The insulation can be installed internally or externally. External insulation is likely to be more expensive but involves less disruption. We would always recommend targeted insulation at convenient times. So, for instance, if you are stripping out a room and re-decorating that would be the time to consider taking insulation measures internally. Similarly it may not be practical to apply external insulation to every wall however – but it may be quite easy and relatively inexpensive to insulate one or two appropriate sold walls.

In our model, insulating the main flank external wall on our detached house would yield savings of £254 a year.

Internal Wall insulation, this can be done with flexible thermal lining or rigid thermal board.

Flexible thermal lining comes in rolls one-meter wide and 12-meters long. It can be effectively applied like wall paper and is fixed to the wall using adhesive. It is made from latex and has a durable glass fibre face that can be decorated or plastered afterwards.

Rigid thermal board is essentially a tile some 2.4x1.2m. Ideally the insulation pad will be approximately 58mm thick and is backed with plaster board 12mm thick, the tile is fixed to the wall using a combination of adhesive and or mechanical fixings. The rigid thermal board can be fixed internally or externally. If fitted internally it can be prepared for decoration or plastering. Externally a render finish can be applied for protection and an attractive finished look.

Our model shows that savings from this type of insulation is much less than for 70mm insulation backed plaster board. The reason for this is that the thermal resistance of thermal flexible lining is much lower than 70mm. So a sold brick wall insulated with insulated flexible lining typically 10mm thick would yield a U value of 1.5 W/m2/K as opposed to 70mm Kingspan Kooltherm K17, which would yield a U value of 0.3 W/m2/K.

The Energy Savings Trust estimates that an average three–bedroom house could see savings of £445- £470 a year from internal or external solid wall insulation.