Revised Building Regulations Aim To Reduce CO² Emissions

On 31 October 2012 the Building Regulations (Northern Ireland) fully revised the existing regulations (2006). Whilst parts saw little/ no revision in standards, the requirements for energy efficiency (Part F, Regulations 38 to 47) have been greatly changed. The aim is to reduce CO² emission levels for new buildings by 25% compared to 2006 regulations.

The revised requirements are set out in Technical Booklets F1 (dwellings) and F2 (buildings other than dwellings), which both use the existing compliance criteria as the 2006 editions.

The use of a notional building (as a theoretical building) is used for the calculation of CO² emission limits for the actual building. The table below reflects the U value changes.

TER/DER assessments must now take account of party walls, using specified U-values rather than calculated values. Care needs to be taken not to conflict with Technical Booklet G, Sound. With regards to the cavity wall insulation industry, it’s now impossible to meet current building regulations using bonded bead for a 100mm cavity in a standard build using conventional building materials such as brick and block.

The required “U” value can only be achieved in a 100 mm cavity when the construction uses possibly light weight insulated block or another specified product.

The various BBA published agrement certificates will state the thermal conductivity properties of the particular product (this is not a U-Value but a Lambda value measured in λ W/mK) and these are then used as part of a wider calculation to determine the thermal transmittance (U value) of specific external wall constructions in accordance with BS EN ISO 6946:2007 and BRE Report BR 443:2006.

The U value of a typical brick and block cavity wall construction will depend on the cavity width and the insulating value of the internal block leaf and finishes.

Calculated U values are often set out in specific tables for bonded bead in agreement certificates and at present the lowest declared product at 0.032 Lambda will only meet a 0.27 U value for a standard built cavity width of 110mm.

The solution to this is that to meet U values for 100 mm the builder will have to use an insulated block or other conforming materials. In most instances new build cavities are now going to and beyond 150 mm and all current grey bonded bead systems will meet the required U values.