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Better windows for better energy efficiency

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Soda ash to make glass: Solvay helping buildings consume less energy

Almost half the energy we consume is used on buildings. One of the reasons for this is the existence of windows, which account for 15 to 25% of a building’s heat loss. Therefore, one of the most efficient ways to improve insulation is to equip buildings with windows that do a better job at keeping the cold (and heat) outside.

Double and even triple glazing were invented for just that – but whatever the technology, the primal element remains glass, for which Solvay is a leading provider of one of the main raw materials needed to manufacture it: soda ash.

From burnt plants to manufacturing plants

Throughout history, soda ash, or sodium carbonate, has always been one of two main ingredients for making glass – the other one being sand. For centuries, it was obtained naturally, from the ashes of sodium-rich plants or from natron deposits. But since the major scientific discoveries of the 18th and 19th centuries, specifically the development of the Solvay process by our founder Ernest Solvay, glass making was revolutionized by industrially produced soda ash.

Note that there are two distinct types of glass: container glass for food and beverages and flat glass for construction, automotive and solar panels. Solvay’s soda ash is chiefly destined to flat glass. “Construction is the main end market for our business unit: it represents 20% of our sales,” says Jean-Charles Djelalian, in charge of strategic marketing and sustainability at Soda Ash & Derivatives. “And as the global leader, we work with all of the world’s leading glass manufacturers.”

If countries are to meet their climate objectives, it’s urgent to accelerate the renovation of existing buildings and equip them with good windows and insulating glazing.

Bernard Savaëte, glass expert

Decades of incremental improvements

Over the past few decades, windows have grown in complexity and efficiency. Up until the mid-20th century, they were only made up of a single pane of glass, offering poor insulation and posing problems such as condensation. “After WWII, due to increasing demand for better insulation, double glazing appeared: two sheets of glass separated by a layer of air, which became commonplace starting in the 1950s”, explains Bernard Savaëte, a renowned glass expert. “And the energy crisis of the 1970s accelerated this trend, as the need to save energy suddenly grew sharply.”

Progressively, a new standard appeared for double-glazed windows that increased their insulation efficiency: 12-14 mm of argon gas, instead of air, between two sealed sheets of glass, which are coated with a low emission film (Low-E), typically silver. Windows possessing all these characteristics enable heat loss reductions of up to 69%. And in climates where the cold is particularly intense, such as in Northern Europe, triple glazing appeared around the 1990s.


In mature markets such as North America, and especially Europe, current regulations impose double glazing for all new constructions. But in these low growth economies, the lion’s share of energy savings resides in the renovation of existing buildings. “If all the buildings in Europe were equipped with double glazing, the energy savings would be tremendous,” says Bernard, adding that though estimates are hard to make, it’s a matter of millions of tons of CO2 that would no longer be emitted, as about 75% of the continent’s buildings are currently ‘energy inefficient.’ “If countries are to meet their climate objectives, it’s urgent to accelerate renovations. And that will automatically boost the global production of sheet glass.” 

Solvay and its soda ash, along with all its other products and solutions that help promote resource efficiency, are up for the challenge!


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