Wall Insulation Guide

In general the insulation is done internally if it is retrofitted, or within the brick courses if it is a new build. The main products for retrofitting insulation on walls are made by the three biggest suppliers Kingspan, Celotex and British Gypsum. These boards come in two varieties, those backed with plasterboard and those not.

Normal Thermal Boards (Not plasterboard backed)

These are foil backed on both sides and are by far and away the most popular selling. Celotex GA4000 range and Kingspan TP10 range make these boards and they are to all intents indistinguishable from a thermal performance perspective. The new regulations have meant that greater and greater thickness are now required to achieve the required U value. For walls this is likely to be in the region of 70mm of insulation but this is very much dependent on the wall construction (i.e. brick or block cavity or non cavity)

Plasterboard Backed (Kingspan K107 & K118, Thermaline Boards and Celotex PL Range)

If you select a plasterboard backed product to go on your wall the main factors to think about are "How am I going to fit the product?" and "How thermally efficient is the product?":

Fixing Choices

  • You can either fix mechanically with screws or you can dot and dab (glue) the product with dry wall adhesive
  • With the Gyproc Thermaline range you can dot and dab or mechanically fix the whole range
  • Kingspan have divided their boards between mechanical fix Kingspan K18 and Dot and Dab Kingspan K17
  • Celotex provides a PL4000 board which can be glued or screwed
Where the choice is to mechanically fix, this is typically achieved by screwing through the insulation, either into battens or direct into the party wall. Screwing into battens is the preferred method as it easier to do and provides a more stable fixing. It also adds an air gap which is necessary where damp may be a issue. Typically a 25mm air gap is required. Dot and Dabbing is the term used to describe putting dollops of adhesive on the wall and pushing the boards into place.

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