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Beating the Heat: The Complete Guide to Solar Control Glass
Beating the Heat: The Complete Guide to Solar Control Glass
How to stop your conservatory or south-facing extension from overheating.
- ☀️ The “Greenhouse Effect”: Standard glass traps solar heat inside, causing conservatories and large extensions to overheat rapidly in the summer months.
- 🛡️ The Technology: High-performance Solar Control Glass uses a microscopic metallic coating to actively reflect up to 75% of solar heat back outside before it enters the room.
- 📉 The Metrics: We measure this performance using “g-values” (solar gain). A lower number means much better cooling performance.
- ✨ The Benefits: Beyond temperature control, it heavily reduces harsh glare for TV/computer screens and blocks 98% of furniture-fading UV rays.
We all love a bright, sun-drenched room—until it becomes a sweltering greenhouse. If you have an older conservatory or a newly built extension featuring large south-facing bi-fold doors, you already know the struggle: it is freezing cold in the winter and unbearably hot from May to September.
Historically, the only solutions were expensive air conditioning systems, heavy blinds that blocked out the view, or dark, unsightly tinted films that peeled over time. Fortunately, modern glass technology has completely evolved.
In this comprehensive technical guide, KJM Group explains the exact science behind Solar Control Glass and details the specific Pilkington products available to transform your home into a comfortable, year-round living space.
Page Contents
1. What is Solar Control Glass? (The Physics)
Solar control glass is a highly engineered glazing product designed to actively reflect infrared heat while still allowing natural visible light to pass through.
Unlike older tinted glass that simply absorbs heat (which often radiated back inwards anyway), modern solar control glass utilises Selective Filtering technology to literally bounce solar radiation away from the building.
This impressive performance is achieved through an invisible, microscopic metallic coating applied to the inner surface of the outer glass pane during manufacture. This coating is “spectrally selective.” It allows Short-Wave Radiation (the visible light you want to see) to pass through easily, but reflects Long-Wave Radiation (the infrared heat you want to avoid) straight back into the atmosphere.
2. The Data: g-Values Explained
To choose the right glass for your project, you need to understand the “g-value” (often referred to as the Solar Factor). This is the metric used to measure exactly how much solar heat enters a room through the glass.
- g-value of 1.0 (100%): Every drop of heat enters the room (equivalent to an open hole in the wall).
- g-value of 0.0 (0%): Absolutely no heat enters the room (equivalent to a solid brick wall).
Standard Clear Glass: Has a high g-value (typically around 0.76), meaning 76% of the sun’s intense heat gets inside.
High-Spec Solar Control Glass: Has a significantly lower g-value (e.g., 0.33), meaning only 33% of the heat gets in, keeping the room drastically cooler.
3. Comparison: Standard vs. Solar Control
Here is the quantitative data comparing standard modern double glazing against Pilkington’s high-performance solar control options to help you understand the sheer difference in performance.
| Glass Type | g-value (Heat In) | Light Transmission | Total Heat Rejection |
|---|---|---|---|
| Standard Clear Double Glazing | 0.76 | 82% | Low (24%) |
| Pilkington Activ™ Blue | 0.33 | 52% | High (67%) |
| Pilkington Suncool™ | 0.37 | 70% | High (63%) |
4. The Pilkington Product Range: Choosing Your Glass
At KJM Group, we partner directly with Pilkington, the world leader in advanced glass technology. Understanding the subtle visual and performance differences between their products is key to getting the right result for your specific room.
Pilkington Product Spotlight
The Look
Features a highly attractive, sky-blue tint.
The Performance
Blocks 67% of Heat. Allows 52% of Light.
Best Application
Conservatory & Orangery Roofs. The blue tint provides excellent, soothing glare reduction for very bright summer days.
The Look
A subtle, neutral grey tint.
The Performance
Blocks 60% of Heat. Allows 59% of Light.
Best Application
Neutral aesthetics. Perfect for homeowners who dislike blue roofs but still critically need high heat rejection from above.
The Look
Virtually Clear to the naked eye.
The Performance
Blocks 65% of Heat. Allows a massive 70% of Light.
Best Application
Vertical Windows & Large Bi-folds. Offers exceptionally high light transmission with elite heat blocking, so your views aren’t darkened.
5. Pros & Cons (The Trade-offs)
Before investing in upgraded glass, it is important to weigh the massive benefits against the minor potential limitations.
✅ The Benefits
- Total Comfort: Makes the room highly usable in peak summer without relying on expensive, energy-hungry A/C units.
- UV Protection: Blocks up to 98% of harmful UV rays, saving your expensive sofas, flooring, and artwork from sun-bleaching and fading.
- Self-Cleaning Features: Activ™ products come with an external coating that actively breaks down organic dirt using sunlight, then washes it away smoothly in the rain.
❌ The Minor Downsides
- Light Loss: Heavily tinted roof products reduce light transmission by 15-40% compared to clear glass (though many find this reduction in harsh glare preferable).
- Initial Cost: This is a premium, highly engineered product, costing more upfront than standard double glazing.
6. Local Advice: Hampshire & Berkshire Conservatories
🏡 Designing for UK South-Facing Gardens
Across our service area—from Andover, Winchester, and Basingstoke up to Newbury and across to Salisbury—south-facing or south-west-facing conservatories can easily reach internal temperatures of over 40°C in the height of summer. For these extreme-exposure projects, our surveyors strongly recommend a combined “fabric first” approach:
- Low g-value glass (like Activ™ Blue) specifically for the roof panels.
- Adequate High-Level Ventilation (manual or automatic roof vents) to allow the rising hot air to quickly escape.
- Solar Control vertical glazing (like Suncool™) if your design features expansive, full-height bi-fold or sliding patio doors facing the sun.
This combined approach actively prevents the solar radiation from entering the room in the first place, which is infinitely more efficient than trying to cool down a boiling room later.
7. Frequently Asked Questions
It completely depends on the specific product chosen. Pilkington Activ™ Blue has a noticeable blue tint, which is highly desirable for conservatory roofs to reduce harsh squinting glare. Pilkington Suncool™, however, is specifically designed for vertical doors and windows; it is virtually clear and largely indistinguishable from standard glass to the naked eye.
It is absolutely essential for conservatory, orangery, and lantern roofs, as overhead glazing is the primary cause of severe overheating. It is also highly recommended for large vertical glazed areas (like wide bi-fold or sliding patio doors), especially if those elevations face directly south or south-west.
Yes. Providing your existing window frames (uPVC, aluminium, or timber) are in good structural condition, you do not need to rip them out. We can simply “de-glaze” the frames and replace the older, inefficient sealed units with new, high-performance solar control units, instantly upgrading the thermal comfort of the room at a fraction of the cost of a full replacement.
No. Solar control glass is combined within a double or triple glazed unit that also features “Low-E” (Low Emissivity) technology on the inner pane. This means while the outer pane reflects the sun’s heat away in summer, the inner pane reflects your central heating back into the room during the winter, giving you excellent year-round temperature regulation.
📚 Explore Our Glass Knowledge Hub
Compare other modern, high-tech glazing technologies below:
Is your conservatory too hot to use?
Contact the glazing experts at KJM Group today. We can upgrade your existing conservatory roof or specify the perfect solar control glass for your new extension project across Hampshire, Berkshire, and Wiltshire.
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Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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