Rooflights: What Are U Values and Why Are They Important?
Increasingly, new build projects as well as existing buildings are maximising the use of natural light together with the thermal properties of modern glass, to create a revolution in how we look at heat retention and accessing light sources.
When you consider the costs involved in paying for artificial light and heat, especially at a time when energy prices are soaring so significantly, rethinking our approach to and reliance on these basic needs makes a lot of sense.
A U value tells us how much heat is lost from a building through different elements, such as windows, walls and floors.
It is a measurement of heat transference, also known as the “overall heat transfer co-efficient”, meaning the higher the number value, the more heat is being lost, and the less environmentally friendly the building is. A lower value therefore indicates greater insulating properties and is more energy efficient.
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Calculating the U Value
The U value of a building element is calculated by working out heat loss for each component of the building. This is determined by the material used, its thickness, and its positioning.
Current building regulations in England and Wales allow for all non-domestic applications, the worst acceptable standard for the thermal performance (U-value) of rooflights in new build work is stated as 2.2 W/m2k. For refurbishment or domestic applications, this figure is reduced to 1.8 W/m2k.
Rooflights are made up of a number of different component materials that each have different properties when it comes to heat transference. Therefore, to find out the U value of this type of element, a number of factors need to be determined.
It is simply not enough to state the glass centre pane U value of the glass unit as this does not represent the U value of the entire rooflight product.
Equally, thermal comparisons between competing rooflight products can only be made when U values for the whole rooflight are considered. A poorly designed triple glazed rooflight product may in fact perform worse than a well-designed double glazed product albeit the centre pane U value of the triple glazed glass unit may be better than that of the double glazed glass unit.
Energy Effecient Rooflights.
Energy efficiency is at the core of our product range at EOS, each of our rooflights boasts U Values significantly lower than current and future building regulations. Our standard fixed products boast a 0.97 W/m2K U Value whereas our ECO Range is tested to a market leading 0.65Wmk system U Value.
In fact our U values are so low that official building standards permit you to increase the amount of glass within your roof area.
So, as well as flooding a building with daylight to naturally enhance the indoor environment, EOS rooflights ensure green energy efficiency by reducing the need for CO2-emitting artificial lighting, whilst guaranteeing that heat isn’t lost unnecessarily.
For green efficient skylights with low U Values, speak to the EOS Rooflights team today
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