Insulation ~ Mineral Wool

Mineral Wool is an inorganic product manufactured from glass or rock. Most commonly seen in the UK in the form of rolls used for loft insulation it is also used in granular form as a cavity wall filler and as rigid slabs in construction. Certain products use recycled glass and can so claim green credentials.


A long-time favourite in the UK, sometimes also know as rock wool.

Although the production of mineral wool consumes relatively large amounts of energy, manufacturers counter this with evidence of far greater energy savings over its installed life.


  • High embodied energy.
  • Fire resistant.
  • The fibres can be an irritant.
  • Versatile and relatively easy to fit.
  • Formaldehyde (a hazardous chemical and known carcinogen) is used in its production. However, mineral wool as a product is ‘unclassifiable as to its carcinogenicity in humans’*.

At 220mm thickness, installed between rafters mineral wool has a thermal conductivity or K value of 0.038 W/m.K.
(Watts per meter Kelvin ~ lower value is a better result)

Cheap … shop around as for example, B&Q will currently provide upto 80 square metres installed for £198 or under £2.50 per square metre.

* classification of mineral wool fibres by the International Agency for Research on Cancer.