You will hear a lot of talk and read a lot of comment on the importance of U values when it comes to house insulation from both manufacturers and installers. In addition there is a whole section of the Building Regulations – Part L – devoted to enforcing certain U value standards throughout the structure of a house and covering the roof,walls,windows and floor areas.
Basically a U value is a measurement of the thermal efficiency of a material or collection of materials and represents how much heat is lost from the inside of a building . The lower the figure the better and also the slower the heat loss.
As some kind of yard stick a new build house has to hit a 0.25 U value overall and an existing solid 9 inch wall on a 1930′s house is rated at 2.05 U value !!
External thermal insulation systems on solid wall properties will typically reduce the heat loss through the walls by around 75% minimum with a resultant significant reduction in heating bills and carbon emissions as well.
For retro fitting to houses with no cavities the Building Regs give a target of 0.3 U value if possible with a maximum figure of 0.7 allowed.