If your windows are more than 15–20 years old, there’s a good chance they’re quietly costing you money every single day. Heat escapes through old frames and single-glazed or early double-glazed units far faster than most homeowners realise — and here in Cornwall, where coastal winds and damp winters push heating systems hard, that loss adds up fast.
So what does upgrading to A-rated windows actually save you? Let’s break it down properly.
What Does the “A-Rating” Actually Mean?
Window energy ratings run on a scale from A++ (best) down to G (worst), set by the British Fenestration Ratings Council (BFRC). The rating is based on three things:
- U-value — how much heat escapes through the glass and frame (lower is better)
- Solar factor — how much free heat from sunlight comes through the glass
- Air leakage — how airtight the window is when closed
A window can only earn an A rating if it performs well across all three, not just one. That’s why two windows that look identical can perform very differently — the frame material, glazing spacer, and seal quality all matter as much as the glass itself.
The Real Cost of Old Windows
According to the Energy Saving Trust, replacing single-glazed windows with A-rated double glazing across an entire average semi-detached home can save around £195–£235 a year on energy bills, depending on fuel prices and how the home is heated. Even replacing older, poorly performing double glazing with modern A-rated units can save a noticeable amount, because glazing technology has moved on significantly in the last 15 years.
For a typical 3-bedroom Cornish home with 8–10 windows, that’s not a small saving — and it’s one that keeps paying back year after year, not just a one-off.
Why Cornwall Homes Lose Even More Heat
Properties near the coast — think St Austell, Fowey, Par, Mevagissey and the surrounding villages — face a double challenge:
- Higher wind loads push harder against poorly sealed frames, increasing air leakage
- Salt-laden air accelerates wear on older frame materials and seals, so windows that were once airtight often aren’t anymore
This means many coastal homes are losing more heat than the national average figures suggest, which makes the case for upgrading even stronger.
What to Look for When Choosing A-Rated Windows
Not all “A-rated” windows are equal in real-world performance. When you’re comparing quotes, ask about:
- Chamber count in the frame (more chambers generally means better insulation)
- Glazing unit thickness and gas fill (argon-filled units perform better than air-filled)
- Warm-edge spacer bars rather than old-style aluminium spacers, which conduct cold
- Multi-point locking for a tighter seal, which also improves security
At St Austell Bay Windows & Plastics, our A-rated uPVC windows and aluminium windows are built to perform in genuinely coastal conditions, not just meet the minimum rating on paper.
uPVC vs Aluminium — Which Saves More?
Both can achieve A-rated performance, but they behave differently:
- uPVC windows have naturally low thermal conductivity, making it easier and often more cost-effective to hit high energy ratings
- Aluminium windows need thermal breaks built into the frame to prevent heat transfer, but modern systems achieve excellent U-values while giving slimmer sightlines and a more contemporary look
Neither is automatically “better” for energy savings — it depends on the specific system, and we’ll always talk you through the real performance figures rather than just quoting a letter grade.
Beyond the Bills: Comfort and Condensation
Energy savings are only part of the story. A-rated windows also:
- Reduce cold spots and draughts near window reveals
- Cut down on condensation, since warmer internal glass surfaces are less prone to moisture forming
- Reduce noise transfer, which matters if you’re near a main road or in an exposed coastal spot
Is It Worth the Investment?
For most homes, yes — particularly if your current windows are single glazed, have failed seals (visible as misting between panes), or are more than two decades old. The combination of ongoing energy savings, improved comfort, and increased home value makes A-rated windows one of the more straightforward home improvements to justify. Every installation also comes with our full guarantee for long-term peace of mind.
Get a Free, No-Obligation Quote
St Austell Bay Windows & Plastics has been supplying and fitting A-rated uPVC and aluminium windows across St Austell, Truro, Fowey, Newquay and the rest of Cornwall since 2005. Our own in-house fitters install every job — no sub-contractors — so you get consistent quality from quote to completion.
Get your free quote today and find out exactly how much you could save.
