GLASS ENGINEERING / SOLAR CONTROL
SOLAR-CONTROL
GLASS
A large glazed area cannot be specified by choosing a “warm” IGU alone. Solar gains, daylight, Ug, reflectance and façade appearance have to be balanced together.
PRINCIPLE
g-value, LT and Ug work together.
g-value describes the share of solar energy transmitted through the glazing. LT describes visible light transmission. Ug describes centre-of-glass thermal transmittance. The right specification depends on façade orientation, glass area, shading, climate and building use.
Solar energy transmitted indoors
Visible light transmission
Centre-of-glass thermal transmittance
Coating selectivity
The figures on this page are there to explain how solar-control glass is selected. For a project, g-value and light transmission are checked on the actual IGU build-up and façade orientation.
WHAT WE CHECK
Specification starts with the problem.
Solar control is not selected in isolation. Glass area, orientation, external shading and the desired neutrality of the façade are considered together.
Orientation comes before a product name
Large south- and west-facing glazed areas usually require stronger solar-gain control. North-facing façades can need a different balance between daylight and heat.
We do not reduce g-value blindly
Excessive solar control can darken interiors and change exterior reflection. We compare g-value with LT and the architectural brief.
Heat-treatment compatibility is checked
Large or thermally stressed panes often need tempering or heat strengthening. The coating and its version must be compatible with the required processing.
Façade consistency is part of the specification
Production batch, coating orientation, reflected colour and consistency between heat-treated and annealed panes matter on large façades.
PRACTICAL EXAMPLE
Example: neutral solar control for residential glazing
Saint-Gobain publishes g = 0.42 and Ug = 1.0 W/m²K for PLANITHERM 4S in a defined double-glazed configuration. It illustrates how one coating can support both summer and winter comfort, while the final build-up still has to be selected for the actual façade.
TECHNICAL SOURCES
START A PROJECT
We specify glass around orientation and façade area.
Send elevations or a window schedule. We can develop an IGU strategy that coordinates solar control, thermal performance, safety and architectural appearance.
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