Traditional Roof Lights
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Pilkington ActivSolar Control
Solar control is a key issue in terms of energy saving. In hot conditions or for homes/buildings with high internal loads, solar control glass is used to minimize solar heat gain by rejecting solar radiation and help control glare. In more temperate conditions it can be used to balance solar control with high levels of natural light.

During the winter, low-emissivity glass can reduce heat loss while allowing high levels of valuable free solar gain to heat homes/buildings with no significant loss in natural light. However, unless combined with solar control, in the summer it can become uncomfortably hot.

The correct choice of glass for your glass unit to be installed in your sliding doors, bifold doors or skylights which will be manufactured with non metallic super spacer bars and argon gas filled cavities between panes which both assist in the non heat transfer between panes and stopping the ingress of moisture points, can help to reduce your capital outlay, running costs and associated carbon emissions of your home/building throughout the year.

Given the variety of house/building designs and climatic conditions and the different levels of exposure to solar radiation during the year, the choice of glass must be able to protect the inside of your home/building to ensure maximum comfort, minimize energy consumption, guarantee safety and, not least, provide the optical and aesthetic qualities that compliment your sliding doors, bifold doors or skylights.

How it works – Pilkington activ Neutral/Blue glass controls solar heat radiation (figure 1 outer pane) from the sun by reflectance, transmittance and absorptance. For solar control purposes these are defined in terms of the following parameters:

Reflectance - The proportion of solar radiation reflected back into the atmosphere.

Direct Transmittance - The proportion of solar radiation transmitted directly through the glass.

Absorptance - The proportion of solar radiation absorbed by the glass with the solar control coating (figure 1 outer pane)

Total Transmittance (also known as g value) -The proportion of solar radiation transmitted through the glass by all means. This is composed of the direct transmittance and that which is absorbed by the glass and re-radiated inwards.

Glass Solar Image
Figure 1
Light transmittance - The proportion of the light that is transmitted by the glass.

Light reflectance - The proportion of the light that is reflected by the glass.

Total Shading coefficient - The ratio between total solar heat transmittance of the glass and that of a single 3 mm thick clear float glass.

Selectivity index - The ratio between light transmittance and total solar heat transmittance


Advances in low-emissivity (low-e) glass technology have made windows an essential contributor to energy conservation and comfort, minimizing heat loss and internal condensation. The measure of heat loss is usually expressed in terms of Ug-value, which is the rate of heat loss in Watts per square metre per degree Kelvin temperature difference between inside and outside (expressed as W/m K); the lower the Ug-value, the better the insulation of the product.

How it works - Effectively, Pilkington Clear low-emissivity (low E) glass will reflect energy back into a building, to achieve much lower heat loss than ordinary float glass. Additionally, different types of low-emissivity glass allow different amounts of passive solar heat gain which helps reduce heating requirements and costs, especially in colder months.

Solar energy enters the building mainly as short wave radiation but, once inside; it is absorbed by objects and re-radiated as long wave radiation. Low-emissivity glass has a coating (figure 1 inner pane) that allows the transmission of the suns short wave radiation but reflects long-wave radiation from the heaters, lights and equipment in the room, providing an effective barrier to heat loss. To maximize energy efficiency all year round, often the ideal glazing solution balances both solar control and low-emissivity performance.

Easy Clean and Tinted glass

An addition to solar control energy efficient glass would be to have the glass outer layer coated (figure 1, Pilkington activ, with or without solar control) with an easy clean layer where the glass will utilize the daylight and rainwater to break down and wash away organic dirt from the exterior surface, minimizing maintenance.

Tints may be added to the glass to reduce glare further and assist the solar control efficiency by further reducing the effects of Infra red (IR) and Ultra Violet (UV) on bleaching furniture.