Pro Installer December 2019 - Issue 81 - Page 33

DECEMBER 2019 | 33 Products Read online at www.proinstaller.co.uk which ultimately means 40% less light entering a building. One of the easiest ways to lower a U-value on a window or rooflight is to increase the thickness of the glazing. A decent double glazed unit will give a centre pane value of 1.0W/m²K and a triple around 0.5W/m²K. Then of course there are some that offer quad glazing, which reduces this figure further. However, it should also be noted that by reducing the U-value in this way, you will be significantly in- creasing the weight of the product, the cost and also the depth of the rooflight profile. If you are working on a Listed Building or in a Conservation area then you will require a conservation rooflight design, which should sit completely flush with your roofline. If you are looking to use quad glazing or modern bulky rooflights to improve ther- mal performance then this will most certainly be to the detriment of the build- ings aesthetics. There are a few excep- tions relating to the ther- mal requirements in certain buildings and it is always a good idea to take profes- sional advice should your project fall into one of the following categories: i. Where the replace- ment roof windows are unable to meet the requirements because of the need to maintain the external appear- ance of the façade or the character of the building, replacement windows should meet a centre pane U-value of 1.2 W/m2K. ii. Buildings which are; Listed in accordance with section 1 of the Planning (Listed Build- ings and Conservation Areas) Act 1990; In a conservation area designated in accord- ance with section 69 of that Act; or Included in the schedule of mon- uments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979; Car- ports. iii. Buildings which are; Listed in accordance with section 1 of the Planning (Listed Build- ings and Conservation Areas) Act 1990; In a conservation area des- ignated in accordance with section 69 of that Act; or Included in the schedule of monuments maintained under section 1 of the Ancient Monuments and Ar- chaeological Areas Act 1979; Used primarily or solely used as places of worship; Stand-alone buildings with floor area less than 50m2; Carports; Temporary building with a planned time of use less than two years. a U-value figure is very important when ‘ both choosing products and in the overall construction of your property. The lower the figure the more thermally efficient a product or building is and this can contribute to reducing heating costs and ultimately helps in the fight against global warming ’ In conclusion, despite the fact that the testing methods for obtaining a rooflight’s thermal perfor- mance could do with an overhaul, a U-value figure is very important when both choosing products and in the overall con- struction of your property. The lower the figure the more thermally efficient a product or building is and this can contribute to reducing heating costs and ultimately helps in the fight against global warming. It is also important that the figures provided are genuine and it is advisa- ble to request proof that U-values being quoted are not only correct but are applicable for the appli- cation that you are using that product. Nowhere is this more important than rooflights because of the current way in which these products are tested. If you have any questions or require further technical information concerning the use of rooflights in your own project, please contact one of the Stella Rooflight team on 01794 745445 or visit www.stellarooflight. co.uk