U value is a measurement given to the thermal insulation qualities of a wall with the lower the figure the better . As a guide a new well insulated home will have a U value of around 0.25 and a solid wall home will generally be around 2.05 to 2.10 !!
The U value is therefore a measure of how quickly heat escapes through a structure to the outside and as a result also how much carbon is leaking through the walls as well. In todays hard pressed times with ever rising heating bills it is very important to have a home with a low U value if you wish to keep those winter bills down.
Typical U values for solid wall houses
Whilst there is a great variety of construction materials and methods within the UK the following table is based around the most commonly found solid wall construction ie a 9 inch solid brick wall with 10mm of internal plaster .
The figures show the net U value achieved by the different external wall insulation materials that are used for thermally cladding the outside walls of our homes.
U Values Achieved
From an initial 2.05 to 2.10 U value the following can be attained:
9 inch solid brick & 10mm plaster
Depth EPS Rockwool Kingspan Phenolic
40mm 0.63 0.62 0.45
50mm 0.54 0.53 0.35
60mm 0.47 0.46 0.30
80mm 0.38 0.37 0.23
100mm 0.31 0.30 0.19
Cement Render Insulation Value
The addition or presence of 25mm of external sand and cement render has virtually no insulation value at all and only reduces the above by 0.01.
Cavity, Blockwork & Timber Frame U values
THINC can also calculate insulation requirements for virtually every type of construction method and we welcome any enquiry for a specialist calculation that you may need.
U Value Improvements
Under the Building Regs Part L1B any new house being built or any existing house having work done on outside walls has to meet certain thermal efficiency standards.These standards are to ensure our homes are nice and warm in winter whilst also being energy efficient and cutting both carbon emissions and energy use.
Expressed in numerical terms the U value measures the ability of a material to retain heat and the speed at which it allows heat to pass through it. The target for a new home is 0.25 U value and for an existing home undergoing renovations to a wall it is 0.3 if possible but no worse than 0.7.
Heat escaping solid walls
Solid Wall U Value
Most of the UK’s solid wall homes are constructed of two brick courses deep totalling 9 inch thick and have an average U value of 2.05 to 2.1 ie the new standards achieve around an 80% increase in thermal performance of the wall.
The Energy Saving Trust estimate an average 3 bed semi could save around £400 per year in heating bills if they took the correct insulation measures.
Home Energy Check
At this time of year in particular - it is snowing quite heavily as I write this on 2nd December – it can be very instructive and financially rewarding to take a step back and really think about ways in which you could save energy and money throughout your home.
Please click a free home energy assessment to take a quick energy road test courtesy of the Energy Saving Trust.
. THINC Wethertex - better for the experience
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.