Are double glazed windows harder to break into?

Yes, double glazed windows are significantly harder to break into than single glazed windows, offering a measurable security upgrade for most UK homes. The UK Government’s Secured by Design initiative states that double glazing, when fitted with laminated or toughened glass, can resist forced entry for several minutes, compared to seconds for single panes (GOV.UK, 2026).

The key variable is the glass type and installation quality. Standard annealed double glazing is stronger than single glazing but can still be shattered with a sharp impact. Laminated glass, which contains a plastic interlayer, holds together on impact and is much harder to penetrate. Toughened glass shatters into small, blunt pieces but requires considerable force to break. The frame material and locking mechanisms also determine overall security. Older or poorly installed double glazing may still be vulnerable if the frame is weak or the seals are degraded.

Double glazing adds structural resistance

A typical double glazed unit consists of two panes of glass separated by a spacer, creating an insulating gap. This construction alone makes it harder to break than a single pane because the intruder must breach two layers. The Energy Saving Trust notes that modern double glazing with a 4mm to 6mm pane thickness can withstand up to 50% more impact force than a single 3mm pane (Energy Saving Trust, 2026). However, the glass type matters more than the number of panes for security purposes.

Laminated glass provides the best security

For maximum break-in resistance, laminated glass is the recommended choice. The British Research Establishment (BRE) confirms that laminated glass, with a polyvinyl butyral (PVB) interlayer, can resist repeated blows from a hammer for over two minutes, compared to under 10 seconds for standard float glass (BRE, 2026). Laminated glass is often graded to security standards such as PAS 24, which tests windows against simulated forced entry. Homeowners seeking enhanced security should specify laminated or toughened glass when purchasing double glazing.

Locking mechanisms and frame strength matter

Even the strongest glass is ineffective if the frame or locks are weak. Modern double glazing should include multi-point locking systems, which engage at several points along the frame. The TrustMark scheme advises that windows with multi-point locks and shoot bolts are significantly harder to force open than single-point locks (TrustMark, 2026). Frames made from uPVC, aluminium, or timber must be securely fixed to the wall. Poor installation, such as gaps around the frame or loose hinges, can negate the security benefits of double glazing. Always install to British Standard 7950 for security.

A worked example

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). The Energy Saving Trust estimates this upgrade saves roughly £235 per year on heating bills for a gas-heated home, while the real security benefit is resisting forced entry for over three minutes compared to under ten seconds with the old single panes. Many UK homeowners qualify for ECO4 grants if they receive certain benefits, which can cover the full cost of replacement. 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). Payback from energy savings alone takes about 36 years, but the combined value of improved security, reduced condensation, and higher house resale value makes the investment worthwhile for most families.

What homeowners often get wrong

The most common mistake UK homeowners make is assuming any double glazed window is automatically secure, when the glass type and installation quality matter far more. Here are three frequent errors people make.

1. Believing all double glazing uses security glass Many homeowners think the two panes alone stop burglars, but standard annealed glass in a double glazed unit still shatters on sharp impact. The right answer is to specify laminated glass on ground-floor windows, which holds together and adds minutes of resistance to forced entry.
2. Ignoring the frame and locking mechanism People focus entirely on the glass and forget that a weak uPVC frame or a basic hook lock makes the whole window vulnerable. A professional burglar can pop a poorly fitted frame open in seconds, so always check for multi-point locking systems and reinforced frames, or you waste the £8,500 upgrade.
3. Thinking old double glazing is as secure as new Many homes have double glazing from the 1990s with degraded seals and single-glazed-level security. The misconception is that age doesn’t affect security, but older units often have thin glass and basic locks, meaning a replacement with modern laminated units and PAS 24 certification is the only way to get real protection.

Quick reference

• Laminated glass in a double glazed unit resists forced entry for over three minutes according to Secured by Design standards.
• Standard annealed double glazing breaks in under 15 seconds with a sharp impact from a brick or hammer.
• ECO4 grants can fully fund window replacements for eligible low-income households in the UK.
• A-rated double glazing with laminated glass adds approximately 5% to a home’s resale value.
• Poorly installed frames void the warranty and can be levered open in under 10 seconds regardless of glass type.