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Cavity Wall Insulation Materials

For most people the most cost-effective insulation material is ‘blown fibre’, which is mineral wool. However, we recommend ‘bead’ materials, which are made of very small polystyrene balls. We install Insta carbon bead. These are more expensive than blown fibre. Our surveyor will discuss with you which product is most suitable for your home, leaving you to make an informed choice.

Mineral Wool

Composition & Durability

The mineral wool used for cavity wall insulation consists of mechanically granulated spun glass or rock wool, treated with a binder or water repellent during manufacture.

They are produced under strict quality control to ensure compliance with the performance requirements of the appropriate British Board of Agrément Certificate: the equipment for blown mineral wool is also required to conform to, and the installation must be carried out in accordance with, a current BBA Certificate for this process.


Thermal Conductivity: For the purpose of U Value calculations to determine if the requirements of the building ( or other statutory ) regulations are met, the thermal conductivity of the insulation may be taken as 0.040 W/MºC.

Density: Typical installed densities range from 18kg/m3 for glass wools to 40kg/m3 for rock wools (depending on individual BBA certificates).

Fire: Blown Mineral Wools are non – combustible, tested to BS 476 : Part 4 : 1970.

Water: Mineral Wool is resistant to water penetration and will not transmit water across the cavity or from below DPC level by capillary action. It does not however act as a water vapour barrier.


Survey: A pre-installation survey is carried out to assess the suitability of the property for the installation of cavity wall insulation.

Site Preparation: Essential ventilation openings such as those providing combustion air or underfloor ventilation, and all flues in the cavity wall must be checked. If adequate sleeving or other cavity closures are not present, installation must not proceed until these openings have been sleeved or otherwise modified to prevent blockage by the insulant.

Installation Procedures

Where a semi–detached or terraced property is to be treated, the insulation is contained by inserting a cavity barrier at the line dividing the properties. This consists of a nylon brush which is retained in the cavity.

  • Injection holes of 22mm or 25mm diameter are drilled at a predetermined pattern/distance (depending on individual BBA certificate).
  • Wool is blown into the cavity via a flexible hose fitted with an injection nozzle, using an approved blowing machine. Filling proceeds from the bottom to the top of the wall and from one end of the elevation to the other.
  • After injection of the insulant, the holes are made good to match the existing finish as closely as possible.

Post Installation Checks: All necessary air vents are checked e.g. those providing underfloor ventilation and combustion air. In all cases flues are carefully checked on completion of the installation by means of an appropriate test to ensure they are not obstructed by the insulant.

Technologically advanced insulation system

The product has been developed and refined over many years to satisfy the ever increasing demand for better, warmer, more energy efficient housing. It out performs all other methods of insulating cavity walls. fast installation: less time at your home compared to blown mineral wool BBA approved provides a unique solution: can be used in ‘hard-to-treat’ cavities that could not be filled in the past cost effective clean installation fewer drilling holes instant effect

Carbon Bead

For performance, safety and durability few insulation materials can match Polypearl Plus. Produced from specially selected premium grade expandable polystyrene the product has been developed and refined over many years giving better thermal resistance than most of its competitors.


• It is high performance insulation
• It's free flowing and fills every inch to a uniform density
• The beads are bonded together to ensure permanent stability
• It maintains the function of the cavity wall by allowing water to drain away naturally
• Installation is quick with no mess and no fuss
• There are various cavity wall insulations materials currently available, but for performance, safety and durability few can match the InstaFibre Carbon Saver Plus

Carbon Bead has been developed and refined over many years and has been rigorously tested by the British Board of Agrement and received their certificate of approval for use in all exposure zones.

Carbon Bead is completely safe to use with NO DANGEROUS FUMES, NO HARMFUL FIBRES TO INHALE and there is NO RISK OF SETTLEMENT taking place after installation and furthermore in the opinion of BRE the materials should prove an acceptable insulation as a precaution against Radon in a new build.

The fuel bill is a major expense which increases year after year. Installing Carbon Bead will dramatically cut the heat loss through the walls and actually make them feel warmer. The rooms will have uniform temperature which will increase without turning up the heating and the building will retain it’s warmth longer after the heating is turned off.

JJ Crump is a trading name of J & J Crump & Son Ltd. Our registered office can be found at 1a Nethermoor Lane, Sheffield, S21 1BZ. We are registered in England No. 4153056 and are authorised and regulated by the Financial Conduct Authority. We are a credit broker and not a lender. We offer credit facilities from one lender.