Typical U values for walls, windows and rooftop insulating materials vary from product to product. In broad terms, the lower the U value, the better, it is materials with lower U values limit heat transmission, and, therefore, you are likely to require less energy to heat your home as a result.
This has created changes in the way we think about designing and constructing our properties in terms of materials, structure and fabrication.
Remember, as mentioned above, lower U values should mean higher resistance to thermal bridging. As you can see, on their own without added insulation, cavity walls have a better U value than solid walls
Typical U Values for Walls
Below are the typical U values you’d expect to measure within a solid wall, an uninsulated cavity wall, and an externally insulated wall of any kind. This process uses W/m²K as units of measurement.
Remember, as mentioned above, lower U values should mean higher resistance to thermal bridging. As you can see, on their own without added insulation, cavity walls have a better U value than solid walls.
- Cavity wall (no insulation) 1.5 W/m²K
- Solid brick wall (no insulation) 2 W/m²K
- Insulated wall 0.18 W/m²K
Why is this so? Because cavity walls have a gap between the inner and outer shell of brickwork that acts as an insulator.
Heat does not travel across dry air as effectively as it does across a material. A solid wall does not contain this gap, and is made up of only one layer of brickwork.
Regardless of the type of wall you have in your home, you can clearly see that an insulated wall offers a much better U value – dropping way below 1 W/ m²K.
By protecting your exterior, you prevent inclement climatic conditions from entering your home, and the heat from your radiators escaping!
Forget Your U Value – Go External!
If you have a cavity wall structure around your house, and you’re thinking of installing cavity wall insulation, you may be concerned about the U value of your material of choice.
This is also true for internal insulation methods for solid walls – as cavity wall insulation is not an option here.
You want the best U value measurement possible from your material of choice, so that you are satisfied your property isn’t losing too much heat.
What we say is – forget material U values! That’s right, forget them! This measurement does not take into account moisture, steam, high winds or any other type of weather condition.
U value tests are conducted in laboratories and in calm environments, so they do not consider rainfall or blistering winds – which doesn’t help if you live in an exposed area, where the onslaught of the elements tests structural integrity to the max!
Instead, opt for external wall insulation as this will prevent heat loss, moisture gain and thermal bridging between the inside and outside of your home all-together.
By protecting your exterior, you prevent inclement climatic conditions from entering your home, and the heat from your radiators escaping.
This will bring the typical U values for walls in your home down to around 0.1 W/m²K. Job done!