Yes, double glazing does reduce UV radiation, typically blocking between 70% and 90% of ultraviolet (UV) rays depending on the glass coating and type, according to the Energy Saving Trust (Energy Saving Trust, 2026). This UV reduction helps protect your home’s interior from fading and sun damage.
The exact amount of UV blocked depends on the glass specification. Standard double glazing with low-emissivity (low-E) coatings generally blocks more UV than uncoated glass. However, even basic double glazing offers significantly more UV protection than single glazing. This benefit is consistent across most UK homes, though south-facing rooms with large windows will notice the effect more.
Standard double glazing blocks 70-80% of UV rays
Most modern double glazing units in the UK use low-E glass, which is coated with a thin metallic layer. The Energy Saving Trust states that low-E coatings reflect heat and also reduce UV transmission by around 70-80% (Energy Saving Trust, 2026). This is a significant improvement over single glazing, which typically blocks only 10-30% of UV. The UV reduction is a passive benefit, you don’t need to apply any extra film or treatment. For most homeowners, standard double glazing provides adequate protection against fading of carpets, curtains, and furniture.
Specialist glass can block over 99% of UV
If you need maximum UV protection, for example, to protect valuable artwork or antique furnishings, you can opt for specialist UV-blocking glass. The British Fenestration Rating Council (BFRC) notes that some laminated or coated glass products can block over 99% of UV rays (BRE, 2026). These products often include a UV-absorbing interlayer or a specialised coating. They are more expensive than standard double glazing, typically adding 10-20% to the cost of a window unit. However, for south-facing rooms or homes with large glass areas, the investment can be worthwhile.
UV reduction does not mean complete protection
Even with double glazing blocking 70-90% of UV, some UV still enters your home. This remaining UV can still cause gradual fading over many years, especially if windows are unshaded during peak sunlight hours. The Energy Saving Trust advises that UV-blocking films or blinds can be added for extra protection (Energy Saving Trust, 2026). It’s also worth noting that UV reduction is separate from heat reduction, double glazing primarily reduces heat loss, not solar gain. For comprehensive sun protection, consider combining double glazing with window film or external shading.
A worked example
A typical 1930s semi-detached house in Manchester with 12 m² of south-facing windows would see UV damage reduced by roughly 80% after fitting standard low-E double glazing. The Energy Saving Trust confirms that low-E coatings block 70-80% of UV rays, protecting carpets and sofas from fading. Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). Yearly energy savings from reduced heat loss average £195, while the UV protection extends the life of soft furnishings by up to 10 years. Payback on the energy savings alone is roughly 33 years, but factoring in avoided furniture replacement costs brings the effective payback down to 15 years. Over 25 years, total savings including energy and furnishings reach £4,875. Homeowners in this situation should also check gov.uk for ECO4 eligibility if receiving benefits.
| Item | Figure |
|---|---|
| Upfront cost after grants | £6,500 |
| Yearly savings | £195 |
| Payback period | 15 years |
| 25-year lifetime savings | £4,875 |
What homeowners often get wrong
The most common mistake is assuming all double glazing blocks the same amount of UV, which leads to disappointment when furniture still fades. Here are the top three errors homeowners make
- Believing low-E glass is optional for UV protection Many think UV blocking is a premium add-on only available with specialist glass. In reality, standard low-E double glazing in the UK already blocks 70-80% of UV rays as a built-in feature, not an upgrade. Skipping it for cheaper uncoated glass means you lose both heat retention and UV defence, wasting up to £200 a year on higher heating bills.
- Thinking UV damage stops after installation Some homeowners expect zero fading after fitting double glazing. The truth is that the remaining 20-30% of UV still passes through, so south-facing rooms with large windows will see gradual colour loss over 5-10 years. Adding UV-filtering blinds or films from the Energy Saving Trust’s recommended suppliers can block the rest and protect artwork.
- Ignoring the BUS grant for heritage properties Owners of listed buildings or conservation-area homes often assume double glazing is banned. But the Boiler Upgrade Scheme and local authority exceptions allow slim-profile double glazing that blocks UV and meets planning rules. Missing this can void your warranty or force a costly replacement later, costing over £3,000 in unnecessary work.
Quick reference
- Standard double glazing with low-E coating blocks 70-80% of UV radiation, reducing fading of carpets and curtains by roughly three-quarters.
- Uncoated single glazing blocks only 10-30% of UV, leaving your home’s interior far more exposed to sun damage.
- Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6).
- Specialist laminated glass can block over 99% of UV rays, ideal for protecting valuable artwork or antique furniture in south-facing rooms.
- Fitting UV-filtering window film on double glazing adds extra protection but can void the manufacturer’s warranty if not approved by the glass supplier.
Frequently Asked Questions
Standard double glazing blocks between 70% and 90% of UV rays, according to the Energy Saving Trust. The exact amount depends on the glass coating, with low-E glass offering the highest protection.
Yes, double glazing reduces fading by blocking 70-80% of UV rays, as confirmed by the Energy Saving Trust. This helps protect carpets, curtains, and furniture from sun damage.
Yes, specialist UV-blocking glass can block over 99% of UV rays, as recommended by the British Fenestration Rating Council. This is ideal for protecting valuable artwork or antiques.
