Which cavity wall insulation is best?

It depends on your specific application and the results to be achieved. Mineral wool products offer good acoustic and fire protection insulation. Urethane and other foam insulants offer higher level of thermal efficiency but have limited acoustic or fire protection properties.

Expanded polystyrene is more competitively priced than mineral wool and urethane. Which wall construction is the most thermally efficient?

As a general rule a standard timber frame construction is more thermally efficient than a brick and block cavity construction, but it does depend on the insulation used. What is the minimum residual cavity for walls? The minimum is 25mm depending on height of wall and product used. Check with your building inspector for confirmation.

Which products, in addition to the insulation, can be included when laying insulation boards on a solid concrete or suspended beam and block floor?

• Vapour control layer (eg. 1000g. polythene) - sits above the insulation.
• Damp proof membrane - sits below the insulation. However, with some insulation boards, the position of a DPM can be either below or above the insulation - see the manufacturers’ instructions.
• Liquid membranes - positioned above the slab.
• Tape - where insulation boards are butted together below a screed / finish, taping the insulation boards will prevent the ingress of screed.