In new build the use of an insulating material can be sprayed readily to any chosen depth, is ideal in achieving the higher values required and eliminating air leakage.
For instance, a typical timber frame wall would have required 50 mm of polyurethane foam under 2002 rules – to meet .0.34w/m²K. Now an increase in thickness of 75mm will achieve a 20% reduction. This gives an acceptable U Value of 0.27W/m²K. Similarly, ground floors change from 40mm to 50mm in required thickness of insulating foam to reach the 0.22m²K target. For single story buildings, where the ground floor represents a high proportion of total space, extra insulation values can be achieved.