Issue 36 2023 - Journal - Page 18
New Clement Steel
Windows - A Sustainable,
Energy-Efficient Choice
Hot on the heels of COP27, with war in the Ukraine continuing and another UK recession
looming, climate change and energy price rises are the topics de jour. As people look for ways
to increase the energy efficiency of their properties, in order to make them more sustainable
and avoid incurring increased costs, it is worth noting that old windows and doors can be
among the most common causes of poor temperature control within a building.
New windows can help to reduce energy costs while also
improving the comfort of a property through better
thermal control and noise proofing. In double glazing,
argon and krypton gases are commonly used between the
two panes of glass, because they are heavier than air and
poor conductors of heat which slow down or even stop
energy from travelling through them. The type of gas
used is one factor affecting the Window Energy Rating
(WER) – to comply with current Building Regulations
all new windows should be rated ‘C’ or above and this is
calculated using several variables including:
The material a new window frame is manufactured from
is also important. From a sustainable point of view, steel
is one of the most recycled materials in construction.
Indeed, new steel requires an element of recycled steel in
its production process. The process of recycling steel is
very straightforward - the steel gets picked up by magnet
and melted down - so there are no complicated separating
procedures to follow. Waste from the manufacture of steel
building products is easily collected and separated for
recycling and on the construction site steel products
generate very little waste.
• Thermal transmittance (U value) – this measures how
much heat can escape through the glass in Kilowatthours, per sq m each year;
As it is so inherently strong, steel can be recycled infinitely
without losing that innate quality, giving it a high value as
a secondary raw material. At the end of its life cycle, a steel
product can be recycled and made into new products that
are of an equivalent standard to the original material.
• Solar factor (G value) – this measures how much solar
energy is gained through your windows from the sun in
Kilowatt-hours, per sq m each year; and,
• Air leakage (L value) – this measures the air leakage,
which should be minimal, in Kilowatt-hours per sq m
each year.
Steel is traditionally made using either the Basic Oxygen
Furnace (BOF) or the Electric Arc Furnace (EAF)
method; however, while the BOF route can only
accommodate 35% recycled steel, the EAF method can
Below, the recently refurbished Ladywell Convent in Surrey. Photography: Laura Kelly, LSK Photo.
