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Glass

Glass

Glass is ubiquitous in our lives and sometimes overseen. Globally 33 billion glass bottles are produced every year for wine production alone. Glass appears throughout commercial and residential interiors — glazing, splashbacks, partitions, mirrors, shelving, balustrades and decorative finishes as well as doors, windows and solar panels outside. Glass is valued for its clarity, durability and recyclability in principle, but the reality of its supply chain, energy intensity and end-of-life recovery is more complicated than ‘glass is infinitely recyclable’ suggests.

Within the glass industry, sustainability efforts have focused on production methods, minimising energy requirements, weight reduction, and cleaner transportation logistics. Core ingredients of glass are minerals - primarily silica sand (structural framework), soda ash (lowers the melting temperature) and limestone (stabiliser). Other additives are included depending on the type of glass being produced.  

Facts

  • UK flat glass (used in windows, doors and partitions) has a recycling rate of just 11%, compared with 32% for container glass such as bottles and jars. Source: Business Waste, Glass Recycling Facts
  • The UK glass industry produces 2.4 million tonnes of glass annually with an average recycled content of only 38%, and emitted 2.2 million tonnes of CO2 in 2021 — equivalent to 2.7% of the UK's total industrial greenhouse gas emissions. Source: Cambridge Institute for Sustainability Leadership, ‘Glass Sector Deep Dive’
  • Using 100% recycled cullet in place of virgin raw materials could reduce the embodied carbon of glass by up to 58%. Source: FEVE, 2016 (cited in CISL Glass Sector Deep Dive)
  • Less than 5% of end-of-life flat glass in the UK is currently recycled back into new flat glass, despite around 26% being remanufactured in other ways. Source: ScienceDirect, Mapping Material Use and Embodied Carbon in UK Construction 

Key Points

Reuse

Before removing or recycling existing glazing, consider whether it can be upgraded in place: solar control film, low-E retrofit film or secondary glazing can improve thermal or acoustic performance without full replacement.

Upgrade

Secondary glazing is particularly relevant in period or listed properties, where replacing original glass isn't possible or desirable.

Low-carbon glass

Products using a mix of recycled content, alternative fuels and green electricity are increasingly available from UK manufacturers — ask whether one is an option for the specification.

Recycled content

Avoid virgin material mineral mining - give preference to glass with the highest proportion of recycled content (cullet) available; ask suppliers to disclose the percentage.

Soda ash 

This is one of the world's largest yet least-known commodities, serving as an essential component in glass manufacturing and numerous everyday items (detergents, chemicals, lithium processing, foodstuffs, and animal feed). As a mined or synthetic material ingredient of solar panels, soda ash also plays a critical part in the global energy transition. The industry lacks standards or verifications to guide responsible production.

Consider salvage and reuse

Consider for architectural or decorative glass elements before specifying new.

Recyclability 

Be aware that coloured and coated glass (low-E, solar control, laminated or toughened) is harder to recycle back into flat glass, since coatings and interlayers must be separated before remelting — ask what coatings are present and how they affect recyclability.

Look for Environmental Product Declarations (EPDs)

Some manufacturers now provide this to compare the lifecycle. While having an EPD doesn’t mean a product is necessarily environmentally good and healthier. But having the EPD means transparency and makes it easy to compare the life-cycle environmental impact of the product when compared to another.

Where full replacement is unavoidable

Ask whether the removed glass can be collected separately for genuine flat-glass-to-flat-glass recycling, rather than being downcycled into lower-grade uses such as aggregate.

Supply chain 

Glass manufacture relies on silica sand, one of the most heavily mined natural resources globally; ask suppliers about sourcing and whether recycled cullet reduces virgin sand extraction in their process.

Glass is heavier than comparable clear materials 

Materials such as acrylic or polycarbonate and can break easily in transit — specify appropriately, particularly for large panels, and consider whether a lighter-weight alternative is suitable for lower-risk applications.

Installation

The primary installation risks are cuts from broken glass or cutting tools, and manual handling injury from large or heavy panels — proper lifting equipment and trained handling reduce both.

Installer safety 

Edge-grinding, polishing or on-site cutting can generate fine dust; where this is required, extraction or wet-cutting methods and appropriate respiratory protection should be used in line with HSE COSHH guidance.

Occupant safety 

Specify appropriate safety glazing (toughened or laminated) in line with UK Building Regulations wherever glass is used at low level, in doors, or in high-traffic areas.

End of use

Ask whether the glass product can be collected for genuine remelting rather than crushed for low-grade uses such as construction aggregate, which forecloses future recycling.

Mirrors, laminated and coated glass

These are more difficult to recycle than plain float glass due to backing materials and interlayers — factor this into specification decisions for items likely to be replaced or discarded.

Alternative recycling 

Where flat-glass-to-flat-glass recycling isn't available, crushed cullet still has genuine secondary uses — glass fibre insulation, glass block and terrazzo aggregate all use recycled glass, and specifying these products supports demand for that recycling stream even if it isn't strictly closed-loop.

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