Exel Composites business unit manager for Australia, Stephen Smith, explains why the market should switch to composite windows and doors.

Since the first aluminium smelter opened in Tasmania in 1955, the aluminium industry has been a key contributor to the Australian economy. As of 2018, the industry produced 96 million tons of aluminium bauxite. While the volume of aluminium offers opportunities for a range of sectors and products, its production is carbon emitting.

Reducing emissions from aluminium production is a challenge of its own but replacing some of its uses with composites can help create more sustainable buildings. Composites such as fibreglass are already used in building applications such as roof, wall and floor insulation — though composite windows and doors are still a rare sight in Australia.

Thermal insulation

Summer temperatures in Australia frequently reach 40 degrees Celsius, so air conditioning is a vital system to help keep buildings cool. In fact, it’s thought that 49% of Australians have some form of air conditioning unit in their homes.

However, air conditioning requires a lot of power to run. The average central air conditioning unit uses 3,000W to 5,000W of power for nine hours of cooling a day. According to Australian electricity provider Blue NRG, ten per cent of the world’s energy use is spent on air conditioning.

A typical home loses around 40% of its energy through windows and doors. If a building’s entry and exit points are not thermally efficient, all that cool air risks — quite literally — going out the door. Aluminium is a highly conductive material, which means heat can pass through it very easily. As a result, the warm air from outdoors easily enters a home, completely counteracting efforts to keep it cool.

Composites have a higher thermal insulation than aluminium, which means they retain internal temperatures and minimise the chances of energy escaping. Ensuring energy does not escape means less heating and cooling is needed to maintain a comfortable temperature indoors. Composites also have a lower thermal expansion, which means they don’t warp in extreme temperatures, so doors and windows don’t become stuck and difficult to open.

Time to change

Keeping homes cool won’t just benefit a homeowner’s utility bills. As well as a reliance on aluminium, Australian infrastructure has also been recognised for its energy inefficiency in recent years. Using energy efficient materials for windows and doors aligns with the latest energy performance requirements assigned by Australia’s National Construction Code (NCC). In 2019, the NCC determined that all new housing in Australia must meet a minimum energy performance of six stars, which is demonstrated though a Nationwide House Energy Rating Scheme (NatHERS) assessment.

A six-star rated home is classed as having good thermal performance, whereas it’s thought that a ten-star rated home may completely eradicate the need for artificial cooling or heating. Before these standards were introduced the average performance of housing was only one and a half stars.

In addition, an energy efficient material contributes to a lower U-value of a window or door, which measures the rate that heat escapes through the frame, glass, seals and spacers. The lower the U-value, the greater the resistance to heat loss. Composites like fibreglass have a similar rate of expansion to glass, further minimising the likelihood of energy escaping.

Improved lifecycle

As well as saving energy, providing a more sustainable solution should also mean that it’s built to last. Composites eliminate corrosion, which also makes them more favourable than aluminium for windows and doors. In Australian climates that feature many coastal and extremely hot environments, aluminium can be more susceptible to corrosion. Often, frequent maintenance or complete replacements are required due to corrosion of the door and window frames, which adds to the lifetime costs of those products.

Corrosion weakens material structure and damages its appearance. Composites, on the other hand, demonstrate stability in a range of temperatures and are ultraviolet (UV) resistant, which prevents colour from excessive fading and delivers a long operational life.

Combined, these properties extend and improve the lifecycle of windows and doors. After all, it’s no use having energy efficient windows and doors if they don’t last long enough to demonstrate their full energy and cost saving potential.

Exel Composites manufactures a range of durable and thermally efficient fibreglass and carbon fibre solutions for window and doors, such as frames, sills and internal stiffener profiles. Profiles are produced using pultrusion and pull-winding continuous manufacturing processes, enabling creation of high-volume products with consistent quality.

While Australia thrives as a leading bauxite producer, the overall energy efficiency of its buildings has proven to be poor. To adhere to the new energy performance requirements laid out by the NCC, material efficiency is crucial. Particularly in Australia’s hot and harsh climates, composites are far better suited to achieving durable and efficient windows and doors.