Following the approval of a new Harmonised European Standard, EN 14064, for Insitu Formed Mineral Wool, the most commonly used product type for the retrofit insulation of masonry cavity walls, the British Board of Agrément (BBA) is now embarking upon a programme to reissue all Certificates for such products using the lambda convention defined with the standard. Simultaneously, and to ensure a level playing field, the BBA are also engaging with the manufacturers of other products that compete in the same market, in particular polystyrene bead, to ensure that customers can have similar levels of confidence in the insulation values quoted. It is the BBA’s intention that all such Certificates will declare thermal conductivity values in accordance with the λ 90/90 convention by the end of 2011.
Insitu formed insulation products are those that are installed by being blown or pumped into lofts, masonry walls or framed constructions; as opposed to products supplied pre-formed in slabs, rolls or boards. The purpose of the new Harmonised European Standard is to provide statistical analysis that ensures that any thermal conductivity values used in calculations are achieved most of the time in practical situations.
It is expected that the 90:90 analysis will result in higher thermal conductivity values for insitu formed insulation products. The Knauf Insulation research and development team are working to ensure that its Supafil range of blown mineral wool products and the specific declared thermal conductivity values are improved to meet the new standard requirement. Currently the average (or λmean) value of measurements is used as the declared value, and because the new method relates to the value (λ90/90) that can be obtained for 90% of production within a 90% confidence level, it will result in an estimated increase (worsening) in declared thermal conductivity value of approximately 10% for existing products used in cavity insulation if no adjustments are made to the product.
Knauf Insulation warns that future specification will therefore need to be carefully considered to ensure that product comparisons for this application are undertaken on a like for like basis.
In particular, as no such standard is yet available for Insitu Formed EPS Bead Insulation, which also currently declares thermal conductivity as a λmean value there is a potential for market distortion until the standard is a requirement for all materials, which the BBA is targeting to achieve by the end of 2011.
Stephen Wise, Technical Development Manager at Knauf Insulation said: “The company welcomes the introduction of a Europe-wide standard, which will eventually aid product specification - once applied across all insulation types. Whereas it is recognised that this does increase the thermal conductivity value for insitu formed mineral wool, Knauf Insulation is confident that this can be offset by ongoing innovation and improvement of its blown mineral wool products. Indeed if the market demands, it will be possible to provide products with lower thermal conductivity than is currently supplied, using existing blowing machinery.”
For further information on the differences between λ90/90 and λmean see BBA reference sheet 40/10 (http://www.bbacerts.co.uk/pdf/040-Lambda%209090.pdf) which states that the λ90/90 value and λmean value cannot be compared.