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.
This metal rooflight system offers considerable flexibility for unheated areas where thermal insulation is not an important criterion. White frames and kerbs are standard but
coloured kerbs are also available. X-Five rooflights can be square, rectangular or circular in shape and single glazed as standard with enhanced UV protected polycarbonate or glass.
A security frame is also available as an option.