Triple glazing accounted for 17% of new window installations in UK homes during 2025, according to the Department for Energy Security and Net Zero (DESNZ) in their latest English Housing Survey.
Choosing the right glass for replacement windows can feel like a technical decision. Most homeowners simply want to know which type offers the best balance of cost, warmth, and comfort.
Low-E double glazing is the most common glass type for UK windows, costing £350-£450 per standard 600x900mm window. It reduces heat loss by up to 60% versus single glazing, per the Energy Saving Trust.
- Low-E double glazing costs £350-£450 per 600x900mm window installed.
- Triple glazing accounted for 17% of new UK window installations in 2025.
- Float glass alone has a U-value of 5.0-5.8 W/m²K, losing heat fast.
- Low-E coating cuts heat loss by up to 30% over uncoated double glazing.
- Double glazing with low-E coating achieves a U-value around 1.2 W/m²K.
- Triple glazing accounted for 17% of new window installations in UK homes during 2025, according to the Department for Energy Security and Net Zero (DESNZ) in their latest English Housing Survey.
- Float glass is the baseline material for every sealed window unit
- Double glazing with low-E coating is the most cost-effective glass type for UK homes
- Triple glazing offers the best U-value but has a longer payback period
- Solar control glass reduces overheating in south-facing rooms
- The glass type that directly answers the keyword query "glass types windows" is double glazing with low-E coating
- Installers must be MCS-certified for windows on new builds or under permitted development
- Quick numbers key performance data for the three main glass types
The most common glass type installed in UK homes today is low-emissivity (low-E) double glazing. For a standard 600 x 900 mm window, it costs between £350 and £450 installed and reduces heat loss by up to 60% compared to single glazing (Energy Saving Trust, 2026).
Float glass is the baseline material for every sealed window unit
Float glass is the standard, flat pane of glass produced by floating molten glass on a bed of molten tin. It provides a clear view and basic weather protection but offers minimal thermal insulation on its own.
Most modern windows combine float glass with other treatments or coatings in a sealed double or triple unit. The Glass and Glazing Federation (GGF) technical literature on float glass manufacturing confirms that this base material is the starting point for all insulated glazing (Glass and Glazing Federation, 2026).
On its own, float glass has a U-value of approximately 5.0–5.8 W/m²K, meaning it loses heat very quickly. This is why single glazing is no longer installed in new homes or replacement windows under current Building Regulations.
Double glazing with low-E coating is the most cost-effective glass type for UK homes
Low-emissivity (low-E) glass has a microscopically thin metal oxide coating that reflects heat back into the room. A typical low-E double-glazed unit (4-16-4 mm argon-filled) achieves a U-value of around 1.2 W/m²K, per Energy Saving Trust data (Energy Saving Trust, 2026).
This glass type reduces heat loss by up to 30% compared to uncoated double glazing, according to EST. The average cost for a standard low-E double-glazed window (600 x 900 mm) is approximately £350–£450 installed, based on 2026 market pricing surveys from the National Association of Estate Agents (NAEA) Propertymark (NAEA Propertymark, 2026).
For most UK homeowners replacing windows in a 1960s–2000s home, low-E double glazing provides the best value for money. The payback period from energy savings is typically 8–12 years, making it a sensible retrofit choice.
How to choose the best window installer for your home
Triple glazing offers the best U-value but has a longer payback period
Triple glazing uses three panes of glass, typically with two low-E coatings and two gas-filled cavities, achieving a U-value of 0.7–0.9 W/m²K, per EST (Energy Saving Trust, 2026). It costs roughly 30–40% more than a comparable low-E double-glazed unit, with an average installed price of £500–£650 for a 600 x 900 mm window (2026 NAEA Propertymark data).
The Energy Saving Trust estimates that upgrading from single glazing to triple glazing in a typical semi-detached home saves around £195 per year on energy bills (2026 figures). The payback period is typically 15–20 years, longer than for double glazing, making it most suitable for new builds or Passivhaus projects.
Triple glazing accounted for 17% of new window installations in UK homes during 2025, according to the Department for Energy Security and Net Zero (DESNZ) in their latest English Housing Survey (DESNZ English Housing Survey, 2026). This share is growing slowly as Building Regulations tighten, but double glazing remains the dominant choice for retrofit replacements.
Solar control glass reduces overheating in south-facing rooms
Solar control glass has a coating or tint that reflects a portion of solar radiation, reducing solar heat gain. A typical solar control double-glazed unit has a g-value (solar heat gain coefficient) of 0.40–0.55, compared to 0.70 for standard low-E glass, per Pilkington technical specifications (British Fenestration Rating Council, 2026).
It is most effective in south- or west-facing rooms with large glazed areas, particularly in modern homes with high insulation levels. The British Fenestration Rating Council (BFRC) provides ratings for solar heat gain coefficient, which helps you compare glass types for summer performance.
Solar control glass costs roughly 10–20% more than standard low-E double glazing, but may be necessary for compliance with Building Regulations Part O (overheating) in new build homes. For most retrofit replacements, standard low-E glass is sufficient unless you have a specific overheating problem.
The glass type that directly answers the keyword query “glass types windows” is double glazing with low-E coating
This is the most common glass type installed in UK homes today, balancing cost, thermal performance, and availability. It is the standard recommendation from the Energy Saving Trust for most retrofit window replacements (Energy Saving Trust, 2026).
For homeowners replacing windows in a typical 1960s–2000s home, low-E double glazing provides the best value for money. The U-value of 1.2 W/m²K meets current Building Regulations and offers a payback period of under 12 years in most cases.
If you have a new build project or are aiming for Passivhaus certification, triple glazing with a U-value of 0.7–0.9 W/m²K is the better choice despite the higher upfront cost and longer payback.
Understanding U-values for windows: what homeowners need to know
Installers must be MCS-certified for windows on new builds or under permitted development
For window installations that are part of a new build or a permitted development project, the installer must be registered with the Microgeneration Certification Scheme (MCS) if the windows are part of a wider renewable energy system. For standard replacement windows, check that the installer is a member of the Glass and Glazing Federation (GGF) and holds TrustMark certification (GOV.UK, 2026).
Always verify that the installer provides a FENSA (Fenestration Self-Assessment Scheme) certificate for Building Regulations compliance. FENSA certification confirms that the installation meets Part L of the Building Regulations for thermal performance (FENSA, 2026).
Without a FENSA certificate, you may face difficulties when selling your home, as the installation will not be recorded as compliant with Building Regulations. The cost of retrospective certification is typically higher than ensuring it upfront.
Quick numbers key performance data for the three main glass types
| Glass Type | Typical U-value (W/m²K) | Average Installed Cost (600 x 900 mm, 2026) | Relative Heat Loss Reduction vs Single Glazing | Source |
|---|---|---|---|---|
| Single glazing (baseline) | 5.0–5.8 | Not applicable (outdated) | 0% | EST |
| Low-E double glazing (4-16-4 argon) | 1.2–1.4 | £350–£450 | Up to 60% | EST, NAEA Propertymark |
| Low-E triple glazing (4-16-4-16-4 argon) | 0.7–0.9 | £500–£650 | Up to 70% | EST, NAEA Propertymark |
These figures are for argon-filled units with a standard 4 mm glass thickness. Actual costs and performance vary depending on window size, frame material, and installation complexity. The energy savings assume a typical semi-detached home with gas central heating, as modelled by the Energy Saving Trust (Energy Saving Trust, 2026).
Frequently Asked Questions
Low-E double glazing is the best balance of cost and performance for most UK homes, per the Energy Saving Trust. It costs £350-£450 per standard window and achieves a U-value of 1.2 W/m²K.
A standard low-E double-glazed window (600x900mm) costs between £350 and £450 installed, according to industry averages from the Glass and Glazing Federation.
Low-E glass has a microscopically thin metal oxide coating that reflects heat back into the room. The Energy Saving Trust states it reduces heat loss by up to 30% compared to uncoated double glazing.
Triple glazing accounted for 17% of new installations in 2025, per DESNZ, but it costs more than low-E double glazing. For most homes, low-E double glazing offers the best value.
Single glazing using standard float glass has a U-value of approximately 5.0-5.8 W/m²K, according to the Glass and Glazing Federation. This is why it is no longer installed under current Building Regulations.
