Robby Branson
A Professional You Can Trust.
Robby Branson Builders Ltd
A Professional You Can Trust.
Robby Branson Builders Ltd
Windows and doors are the second most popular upgrade when it comes to conservatories—and with good reason. To be officially classed as a conservatory and take full advantage of permitted development rules (including avoiding the need for full building regulations), your structure must have at least 50% glazed walls and 75% glazed roof area.
No one typically comes out with a tape measure to check exact percentages, but we have seen cases where a neighbour, unaware of the rules, contacted the local council assuming a full extension was being built. So, to avoid unnecessary hassle, we always recommend letting your neighbours know in advance—even if relations aren’t great. A simple note through the door can prevent surprises.
The range of window and door types on the market today is vast, and understanding some of the technical basics can help you make a more informed decision.
Glass units for windows and doors can vary slightly from those used in roofing, but the core principle is the same. One key difference is that toughened (tempered) safety glass is only required in certain areas—mainly doors or windows set below 800mm from the finished floor. Self-cleaning glass, while common in conservatory roofs, is rarely used in the side glazing unless requested.
Double-glazed units are rated as a complete unit, not by the individual panes. The British Fenestration Rating Council (BFRC) grades thermal performance from G (worst) to A++ (best), similar to how appliances are rated. So, when someone says a window is “A-rated,” it means it has excellent thermal efficiency overall—not just good glass.
Improvements in frame design have increased energy efficiency across all materials, though the effect on total heat loss is modest compared to the large glazed areas in conservatories.
1: uPVC (PVCu) frames are typically the most thermally efficient due to how they’re extruded during manufacture. Many achieve U-values around 1.2 or better and are fully recyclable.
2: Timber frames can match these figures, but only the higher-end, engineered timber models reach similar thermal performance. Standard timber frames are often closer to 1.6 U-value, unless you invest in multi-layer hardwood constructions.
3: Aluminium frames, once poor performers, have now caught up thanks to thermal break technology—but U-values still vary widely between manufacturers, so it’s important to check specs carefully.
4: Hybrid frames, like those from Andersen (a high-end American manufacturer we’ve worked with), combine the warmth of timber with the durability of aluminium cladding. These are premium products with a long lifespan.
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