Choose a suitable U-value

U-values might seem a pretty dull subject, however it is absolutely key to understand them so that you can insulate your home with the most appropriate material. 

Thermal transmittance, also known as U-value, is the rate of transfer of heat through a structure (which can be a single material or a composite), divided by the difference in temperature across that structure. The units of measurement are W/m²K and indicates how much heat per unit of time that flows through an area of 1m² at a constant temperature difference of 1K (1°C) between warm and cold side of the structure. The better-insulated a structure is, the lower the U-value will be.

Both the glass and the frame are taken into consideration when calculating a product’s constructed U-value. We offer five U-values from 1.4 through to ‘Passive House’ compatible products in the low U-value of 0.7. Although a U value as low as 0.7 sounds very impressive, the additional energy saved is small. The key benefits are really to do with comfort. If the walls, roof and floor of a house are insulated, and the glazing ignored then there is a risk of cold spots surrounding the windows at night, which cause draughts, draw heat away, with resulting in the potential for condensation.

Choose a suitable U-value for your project by considering the overall energy efficiency of your home. A period property with little or no wall insulation is likely to leak more energy than a property built in the last 10 years, therefore, a U-value of 1.4 or 1.2 will be appropriate as the overall heat loss from the property can only be countered so far with energy efficient windows. Similarly, fitting 0.7 U-value windows in a standard new build project will cost up to 50% more but will only reduce overall house heat loss by around 5%.

Broxwood Windows & Doors product U-values

Standard, Broxwood’s entry level product, out performs the UK building standard requirement for new build projects.They are exceptional value and are suitable for new build and renovation projects.

Our ThermaSave windows provide real savings and are ideal for new build or replacing windows in an older style property.
How well insulated is the rest of the building? Our ThermaPlus windows are suitable for replacing windows in a properly insulated property or for a new build project.
Broxwood’s technically advanced Ultra product is compatible for use in a Passive House project or a building where your overall intention is to be as carbon neutral as possible.