X-Three Rooflight
This thermally broken, metal rooflight offers considerable flexibility whilst complying with the maximum allowable U value (under Part L) of 2.2. Frames and kerbs are finished in white—standard colour—coloured kerbs are also available. X-Three rooflights can have double glazed or triple glazed polycarbonate. The integral cascade water management system ensures that moisture drains to the outside of the building and air leakage meets Part L criteria. A security frame is also available as an option.
U Value Calculation |
The U value of a rooflight is calculated by dividing the heat transfer across the system (measured in Watts) by the environmental temperature difference across the test element (measured in degrees K) multiplied by the area of the aperture in the surround panel—called the projected area (measured in m²). This latter dimension is equivalent to the opening in the building envelope. One consequence of this is that the ‘U’ value of the product will increase as it gets deeper, despite the thermal properties of the individual components staying the same.
The building energy software SBEM uses the actual area (often called the developed area) of the product, to calculate the heat transfer through the product.
To show what this value is, a “supplemental” U value has been calculated using developed area and it is this relevant value that we quote in this document. |
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How to specify Xtralite rooflights |
If you need to know more about the elements that make up the X-Three rooflight, click on the following for more information: Understanding glazingUnderstanding ventilationUnderstanding roof fixing and security |
If you would like to specify exactly which X-Three configuration you require, click on the following to go to the specification guide: Go to specification guide |
To find a full range of PDF and CAD drawings for the Xtralite range, click on the following to go to the downloads section: Go to downloads section |