Suscons plasticĀ® insulation materials

The most important requirement for any insulation material is that it consistently provides the designed resistance to the passage of heat throughout the lifetime of the building. The properties of traditional cavity wall insulation materials are published by the various manufacturers. Therefore, the required properties for new cavity wall materials need to be equivalent to these in terms of performance but also there are additional requirements which are part of the design process:

  • Ease of installation: The ultimate performance will be determined by how effectively a builder can install the material using conventional skills.
  • Shrinkage, compaction, settlement: Some materials are likely to suffer a degree of dimensional instability during their installed life. In many instances, this is anticipated and can be overcome through careful design and installation methods. In all other instances, the specifier should seek guidance concerning associated risks from the insulation manufacturer, particularly where materials have not had an established record of installed performance.
  • Protection against moisture: Some insulation materials will suffer a degradation of performance when moist or wet. The designer should, through careful detailing, ensure that vulnerable insulation is protected from moisture. If moisture is a high risk, then a suitably resistant material should be specified.

Because the thermal properties of individual materials vary, conductivity values need to be checked. These values can then be used to calculate the minimum insulation thickness. Thermal transmittance, also known as U-value, is the rate of transfer of heat through a structure which can be a single material or a composite, divided by the difference in temperature across that structure. The better insulated a structure is, the lower the U-value will be. Workmanship and installation standards can strongly affect the thermal transmittance. If insulation is poorly fitted, with gaps and cold bridges, then the thermal transmittance can be considerably higher than desired. Thermal transmittance takes heat loss due to conduction, convection and radiation into account.

The U-value of an insulated cavity wall can be influenced by several factors, including the following:

  • Thickness of the insulation.
  • Thermal conductivity of the insulation that depends upon the type of material used, its density and the environmental conditions to which the material is subject.
  • The presence of any air gaps or voids in the insulation and the distribution of these.
  • The presence of any areas in the insulation where the insulation is of lower than normal compactness or where the material is inhomogeneous.
  • Air movement through and around the insulation which in turn is likely to be influenced by convection, external wind conditions and the air-tightness of other parts of the wall construction.
  • Thermal bridging of the insulation caused by wall ties, mortar snots or other obstructions within the cavity.
  • The grade or density of the concrete blocks forming the inner leaf of the cavity wall.