Xtralite are concerned over the accuracy of U values claimed for building components - particularly rooflights - and the impact that this may have on the long-term energy efficiency of our buildings. Xtralite believes that U-values submitted for Building Regulation approval must reflect those that will actually be found on site and has sought expert advice on how to achieve this goal.www.xtralite.co.ukUnit 9/Spencer Rd, NE24 5TG