Currently, Approved Document L of the Building Regulations contains guidance on the thermal insulation performance of buildings, classified in terms of an element or a building's U-value. The simple calculations provided in Part L, taken together with manufacturers' published thermal conductivity, or thermal resistance data, makes working out a U-value a relatively simple process.
Some of the materials used for thermal insulation are also used for acoustic insulation. For example, mineral fibre, a common thermal insulation product, can be used as a resilient layer beneath a floating floor to improve the impact sound insulation of separating floors. But the information permitting a straightforward assessment of its sound insulation properties is not readily available.
The guidance on floating floors in Building Regulations Approved Document E describes resilient layers in terms of material density and thickness only. The material parameter that would allow the calculation of impact sound insulation in the same way that thermal insulation can be calculated is not included. Nor is it routinely given in manufacturers' literature. This parameter is the material's dynamic stiffness - its resistance to bend or oscillate - and is defined as the ratio of dynamic force to dynamic displacement.
With the introduction of draft product standards for thermally insulating materials and the wider use of BS EN 29052-1:1992, for measuring the dynamic stiffness of resilient materials used under floating floors, this situation may be about to change. Furthermore, a move towards the adoption of more useful product descriptors may also be hastened by the imminent revision of Building Regulations Approved Document E. Soon it may be possible to assess accurately the sound insulation of elements in the same way as we do the thermal performance.