Spotlight: Different Cavity Wall Insulation Materials.

There are two main types of cavity wall insulation that you can have installed by Primus Energy. These are whitewool and expanded polystyrene bead. Both materials are approved by the British Board of Agrement (BBA) for the filling of cavity walls, and both have advantages, and particular suitabilities.

About U Values – the performance of cavity wall insulation is measured with a U Value. The lower the U Value, the less heat will escape from your home, and the warmer you will be. U Values take into account the materials that the cavity walls are made of, as well as the width of the cavity, and so absolute U Values for the entire installation will vary with each property. All materials carry their own U Values, which will work in conjunction with your existing walls to hopefully provide you with as low a U Value as possible.


Whitewool is a molten glass fibre coated with a silicone oil. This gives the product a coating that protects it from minor water penetration. This makes it ideal for homes in urban or suburban areas.

Advantages of having whitewool insulation

  • BBA approved product
  • No combustible material is usedWHITEWOOL IMAGE2
  • Thermal conductivity of 0.034U means that the heat will stay in your home
  • Rot proof
  • 2 and a half hour fitting process – for the average sized 3 bedroom, two-storey, semi-detached house
  • 25 Year Guarantee

Disadvantages of having whitewool insulation

  • If installed incorrectly and fibres are released from the cavity wall, it can cause respiratory issues
  • Only waterproof to a certain extent – in rural or coastal areas, the amount of moisture will likely penetrate the material, leaving you with cold spots
  • Not recommended for use in three-storey properties

Expanded polystyrene bead

Expanded polystyrene bead insulation is a grey material that is injPOLYBEAD 2ected into the cavity walls with a bonded glue agent. This creates a solid mass in the cavity to prevent heat loss. The bonding agent provides complete water resistance throughout the entire cavity, meaning this product is ideal for those in rural and coastal ideas – where the risk of bad weathering is much higher.

Advantages of having expanded polystyrene bead insulation

  • BBA approved product
  • Non-combustible product
  • No harmful fibres
  • Thermal conductivity of 0.033U – keeping the heat inside POLYBEAD IMAGEyour home
  • Rot proof – completely water resistant once installed
  • Shorter, two hour fitting process – for the average sized 3 bedroom, two-storey, semi-detached house
  • Can be used in three-storey, hard-to-treat properties
  • 25 year guarantee

As standard, Primus Energy fits using expanded polystyrene bead insulation; due to it’s better U Value, ease of installation and the ability to use it with hard-to-treat properties. Some customers can and do opt for whitewool, and we are happy to accommodate this.