Insulation ~ Phenolic foam

Phenolic foam insulation is made by combining phenol-formaldehyde resin (note the presence of formaldehyde, a hazardous chemical and known carcinogen), a foaming agent and a hardener. When all three are mixed an exothermic reaction causes foaming followed by rapid setting.


Usually now available as rigid boards or panels sometimes as a backing to plaster or chip board.


  • Relatively low embodied energy – in comparison to similar products.
  • Good fire performance. Very low flame spread, negligible smoke emission and very low levels of toxic gas emission.
  • Can be cut and shaped accurately. Often used to closely insulate pipes and can be reused.
  • Lightweight, strong and durable in higher density applications.
  • Can shrink. If applied as a foam then it can shrink when cured.
  • Moisture resistant.

From 0.018 W/m.K, but typically in the range 0.020 – 0.023 W/m.K (Watts per meter Kelvin ~ lower value is a better result)

Kingspan Kooltherm is available for around £8 square metre.