A significant portion of energy enters and leaves a building through windows, which can account for up to 30 percent of heat loss. With intelligent design and the choice of high-efficiency components, a building’s energy consumption can be substantially reduced. The slender lines of steel frames enhance the glass-to-frame ratio. As the thermal performance of windows is dictated more by the choice of insulating glass than the material of the frame, even solid steel windows can demonstrate compliance with the energy conservation requirements of the Build­ing Regulations. But to optimize the energy performance of windows the first consideration is passive design. Natural light and heat flow through a window can be controlled to some extent through appropriate size and solar orientation. Larger windows have more potential to lose or gain heat than smaller windows, and south-facing windows let through more heat and light than north-facing windows.

The steel bil­lets, rods and strips, from which steel window profiles are formed, is basic steel smelted from almost 100% recycled steel scrap. At the end of their life, steel windows can be systematically dis­mantled and the frames, fittings and glass recycled. Recycling of steel avoids the depletion of non-renewable resources and end-of-life waste disposal impacts. The ”green” credentials of steel windows are recognized by the Building Re­search Establishment “Green Guide”.

One of the most significant attributes of a sustainable building product is how long it will last before it needs to be replaced. If a product needs to be replaced every 15 years, the product’s overall environmental impact — and cost to the home owner — is far greater than a product that may only need to be replaced every 30 or even 60 years. Many innovative designs of the Modern Movement, listed buildings commissioned by patrons of the Arts & Crafts Movement, civic monuments of the Edwardian era, and examples of 1930s Art Deco, are characterized by steel windows, which are still in good working order; this demonstrates the longevity of steel when properly serviced and maintained.