Part L | U Values | Sunsquare
Sunsquare

Sunsquare: The market leaders in skylight and roof light design and installation

If you are planning to install new windows and doors, you should be made aware of the need to comply with the requirements of the Building Regulations regarding the amount of heat that can pass through a window or door, including the frame. This is measured as a U-value.

These requirements are relevant to rooflights too and the Building Regulations’ Approved Document L-1B, Table 1 outlines the maximum U-values allowed during the installation of new flat roof skylights, as well as other windows and doors.

Updated back in April 2016, Approved Document L1B covers the Conservation of fuel and power in existing dwellings and subsequent amendments.

Approved Document L1B places rooflights under the umbrella of ‘controlled fittings’ i.e. a new window, roof window, rooflight or door that also incorporates a new frame. In the event that glazing is replaced in an existing dwelling but the existing framework is maintained, this is not regarded as a controlled fitting and, as such, is not notifiable and does not have to meet Part L standards.

In addition, Approved Document L1B states that if a window is enlarged – or a new one is created – the area of rooflights should not exceed 25% of the total floor area of the dwelling unless compensating measures are incorporated elsewhere in the project.

The U-values for rooflights given in Approved Document L1B are based on the U-value having been assessed in the vertical position. For units assessed in a plane other than a vertical position, the standards within Approved Document L1B should be modified by making adjustments in relation to the slope of the unit as noted in BR 443.

At Sunsquare, our state-of-the-art manufacturing centre enables us to provide accurate calculations of the U-values of every single rooflight that leaves our factory. All Sunsquare skylights comfortably surpass Building Regulations requirements with U-values below the 1.4 U-value threshold.

Please find below a list of U-Values for our stock products available to purchase in our online store.

If you are ordering a bespoke skylight, we will happily provide calculated U-Values - just contact our Sales Team for more information.

Rooflight type

Size

U-value (rooflight)

U-value

(upstand & rooflight)

Weight (kg)

Square-shaped SkyView

800x800mm

1.23W/m²K

0.93W/m²K

46kg

Square-shaped SkyView

1000x1000mm

1.21W/m²K

0.95W/m²K

64kg

Square-shaped SkyView

1200x1200mm

1.19W/m²K

0.94W/m²K

86Kg

Square-shaped SkyView

1400x1400mm

1.18W/m²K

0.98W/m²K

110Kg

Square-shaped SkyView

1500x1500mm

1.17W/m²K

0.98W/m²K

124Kg

Elongated SkyView

1000x1500mm

1.19W/m²K

0.97W/m²K

89kg

Elongated SkyView

1200x1500mm

1.18W/m²K

0.97W/m²K

103Kg

Elongated SkyView

1000x2000mm

1.18W/m²K

0.97W/m²K

114kg

Elongated SkyView

1000x2500mm

1.18W/m²K

0.98W/m²K

139kg

Elongated SkyView

1000x3000mm

1.17W/m²K

0.98W/m²K

164kg

Aero Electric Vent

1000x1000mm

1.40W/m²K

1.13W/m²K

86kg

Aero Electric Vent

1000x1500mm

1.37W/m²K

1.13W/m²K

114kg

Aero Electric Vent

1000x2000mm

1.35W/m²K

1.13W/m²K

143kg

Aero Electric Access

1000x1000mm

1.40W/m²K

  -

93kg

Aero Electric Access

1000x1500mm

1.37W/m²K

  -

122kg

Aero Electric Access

1000x2000mm

1.35W/m²K

  -

151kg

Pyramid 30° Square

1000x1000mm

1.45W/m²K

1.17W/m²K

71kg

Pyramid 30° Square

1200x1200mm

1.45W/m²K

1.17W/m²K

94Kg

Pyramid 30° Lantern

1000x1500mm

1.42W/m²K

1.18W/m²K

98kg

Pyramid 30° Lantern

1000x2000mm

1.40W/m²K

1.18W/m²K

124kg

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