During long, sunny summers, homes with large glazed areas can heat up like a greenhouse. We explain how solar control glass works, the concepts of g-value and light transmittance, and how to choose the right glass for each facade orientation.
In Ortaca and the surrounding area, summer is a sunny, hot season that starts in May and lasts until mid-October. In this climate, living rooms with large glazed areas, west-facing bedrooms and glazed balconies can turn into a greenhouse in the afternoon. Running the air conditioning harder is one solution, but the energy bill rises accordingly. Solar control glass offers a lasting solution by stopping a large share of the heat before it even enters through the glass. In this article we explain how solar control glass works and how to make the right choice.
Why Does Glass Heat Up a Home?
Sunlight passes through the glass and strikes the floor, furniture and walls inside. These surfaces warm up and emit heat as long-wave radiation. However, this radiation cannot easily escape back out through the glass and is trapped inside. Known as the greenhouse effect, this causes the indoor temperature to rise quickly, especially on west facades that receive direct afternoon sun.
Standard double glazing reduces heat conduction, but provides limited protection against heat arriving with solar radiation. For this reason, in hot climates you need to look not only at the U-value but also at the glass’s solar energy transmittance.
g-Value and Light Transmittance
Two key values stand out when assessing solar control glass:
- g-value (solar energy transmittance): Shows how much of the total solar energy falling on the glass passes inside. It is expressed between 0 and 1; the lower the value, the less solar heat enters.
- Light transmittance (LT): Shows what percentage of visible light passes through the glass. A high value means a brighter interior.
An ideal solar control glass lets in as much light as possible while keeping the heat outside. The ratio of light transmittance to g-value is called "selectivity"; the higher this ratio, the more heat the glass blocks while maintaining brightness.
How Does Solar Control Glass Work?
The solar control glass used today works with very thin metal oxide layers applied to the glass surface. These coatings reflect most of the infrared part of solar radiation while transmitting a large share of visible light. The coating is applied to the inner face of the outer pane of the double-glazed unit (surface 2), where it is protected from the elements and reflects heat before it gets in.
Combined glass, which brings thermal insulation and solar control together in a single coating, gives a window that stays cool in summer and warm in winter. In climates like ours, where the summer cooling load exceeds the winter heating load, this type of glass is particularly advantageous.
Comparison Table
| Glass type | Approximate g-value | Light transmittance | Suitable use |
|---|---|---|---|
| Standard clear double glazing | 0.75–0.78 | Very high | North facades, shaded areas |
| Thermal Low-E double glazing | 0.55–0.63 | High | East and north facades |
| Combined solar control + Low-E | 0.30–0.45 | Medium-high | South and west facades |
| Reflective solar control glass | 0.20–0.35 | Low-medium | Facades with very intense sun |
Choosing by Facade Orientation
- West facade: Low-angle sun in the afternoon and early evening causes the most heating. Here, combined glass with a low g-value makes the biggest difference.
- South facade: Because the sun is high in summer, eaves and balcony projections provide some shade; still, a solar control coating is recommended for large glazed areas.
- East facade: Morning sun is gentler; thermal Low-E glass is often sufficient.
- North facade: With little direct sun, preserving daylight should be the priority.
Things to Keep in Mind
Solar control glass comes in different tints and levels of reflectivity. Highly reflective glass can look like a mirror from outside and may not be preferred in some residential areas for reasons of facade harmony. Neutral-looking combined glass offers both a natural appearance and good solar control. In addition, very low light transmittance can leave the interior dim during the day and increase the need for lighting, so striking this balance is important.
Solar control glass does not solve everything on its own. It gives the best results when used together with shading measures such as shutters, awnings, external blinds and planting. Choosing solar control glass for glazed balconies also keeps the balcony usable on summer afternoons.
Holiday Homes and Rental Villas
In holiday homes around Dalyan, Sarıgerme and Dalaman, guests usually stay during the hottest months. Solar control glass reduces the air-conditioning load, lowering running costs and increasing guest comfort. Slowing down the fading of furniture, parquet and textiles in the sun is an added benefit.
Conclusion
The most lasting way to stay cool in Ortaca’s long, hot summers is to stop heat before it even enters through the glass. The right g-value, sufficient light transmittance and glass suited to the facade orientation offer both energy savings and comfort. During a free site survey our team examines the sun exposure of your facades and recommends the right glazing unit for each window.
