Glass

Glass has become popular in modern construction due to its aesthetic aspects and transparency, which allows large amounts of natural light to enter a building, improving the comfort of tenants and users.

Environmental impact

The environmental impact of glass production is associated predominantly with raw materials consumption (i.e., quartz sand, sodium carbonate, and calcium oxide) and high-intensity production processes resulting in pollutants emission (e.g., greenhouse gases, nitrogen oxides, sulfur oxides). Additionally, due to their fragility, the transportation and assembly of glass components require more vehicles and special equipment and, thus, more fuel-consuming. Lastly, glass affects energy consumption during the building operation as its relatively low thermal insulation can amplify heat loss and increase energy demand for heating. Glass is, however, a material that can be easily recycled without losing its original properties. Recycling glass can require much less energy than manufacturing it, so the greater the amount of glass recycled, the less energy is used to produce new glass, minimising its environmental impact.

How to reuse and recycle

• The direct reuse of glass elements: direct glass reuse is often associated with technical problems due to glass fragility and disassembly problems. However, glass elements are being used successfully in construction, as in the case of the facade and roof made of glass from end-of-life vehicles at the Glass Chapel in Masons Bend (USA).

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There are several challenges related to reusing of old windows, such as, for example:

• shorter lifetime than new windows;

• poorer properties, sometimes even not meeting current requirements (e.g., U-factor values);

• containing hazardous substances;

• often not matching the existing windows in refurbishment projects.

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Despite the above challenges, it is possible to dismantle windows into individual elements (i.e., frame, glazing/glass, and other functional parts) and reuse them separately. This also allows for easier and safer transport of the individual elements. An Icelandic example of such is Lendager Island's reusing of glass from Smáratorg together with waste wood from Húsasmiðjan as a partition wall in their office. There are also windows designed for disassembly available on the market (e.g., Velfac's).

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Most commonly, however, windows from surplus/unclaimed or mistaken orders are reused. An example is a Háteigsvegur 59 project in which several windows from Gluggagerðin were reused.

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• Production of glass components and products from cullet: cullet can be recycled many times, allowing the production of new products, such as facade components, balustrades, doors, windows, and lighting, for example.

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It is essential to sort glass waste properly, considering its colour, type, and production method. Proper sorting ensures the quality of the material during processing as the glass batch can become contaminated without proper sorting, and thus, its quality can deteriorate significantly.

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• Production of insulation from cullet: cullet can be used in producing insulation materials, such as glass wool or foam glass, which reduce energy consumption in buildings and improve room acoustics.

• Production of building materials from cullet: cullet can be used as a substitute for raw materials used in the production of building materials, for example, as a substitute for aggregate in the production of concrete or as a source of silicon in the production of ceramic products or bricks.

Sources and further reading

1)    The CIRCON's project website and compendium