Steel vs Aluminium Framed Glazing

Many homeowners opt for steel windows or are cautious about replacing them due to the aesthetic it gives the house. The idea of changing these windows to anything else can be daunting.

However, as modern glazing technology has advanced, the benefits of using aluminium framed windows have become more appealing. The use of steel against aluminium is at the forefront of the argument, as both offer great properties when considering updating your home.

Both materials have their own great characteristics which can make it difficult to know which material is right for your project. There are many factors to consider and this article will explain which factors should be considered to ensure you choose the right glazing for your project.

steel look aluminium casement doors with side lights and steel look casement window


Aluminium’s main advantage over steel would be how cost-effective the material and manufacturing process is in comparison with using steel.

The complexity of manufacturing that steel must go through in order to produce a window frame often results in a higher price.

The cost of steel alone would factor into the overall outlay on your development project as it is a considerably more expensive material.



Steel frames require a great amount of maintenance as they must be treated and checked regularly. This must be undertaken to prohibit the natural occurrence of rust and corrosion that steel can be plagued with if not kept protected.

Once aluminium has been powder coated and finished in the desired colour it will not require any further care, other than being occasionally cleaned with minimal effort and products.

There are a few steps that can be taken to ensure the longevity of your aluminium glazing, which you can read more about in our technical advice article on the topic.

steel patio doors designed as a casement door with sidelights and dark steel framed glazing
sieger legacy tilt and turn aluminium windows with grey frames on a traditional English country home

Frames and Sightlines

Steels main advantage over aluminium would be its strength, as steel is 3 times stronger than aluminium it tends to be able to offer smaller frames. Slim frames help to create a light-filled living space, offering panoramic views and inviting a vast amount of natural light into the property.

That being said, the use of steel would make the frames and doors heavier in comparison to an aluminium frame requiring more effort to open and close.

Sieger has engineered aluminium-framed glazing with some of the most minimal sightlines on the market. Our slim framed sliding doors have sightlines as small as 20mm and the Sieger Lux Bifold Door is the slimmest aluminium framed bifold door available on the market.

To achieve steel look aluminium windows and doors, glazing bars are used to mimic the industrial style. True glazing bars have a sightline of 48mm and applied bars can be as slim as 25mm.

Sieger’s Legacy Range is specifically designed to have the aesthetic of traditional steel glazing systems but without the disadvantages. As aluminium glazing is now able to offer ultra slim sightlines but with the benefit of being more cost effective and lightweight, it is often chosen over steel.

Our Legacy Range includes a casement door, a bifold door, a conservation rooflight and a range of window designs. All of these systems are flexible in design and can be manufactured to suit specific requirements. 

The aluminium manufacturing process is more simplified and refined. The frames are crimped and have mechanical joints allowing them to be easily slotted and fixed together in comparison to steel.

Aluminium is extremely robust and flexible allowing it to be easily framed to hold the glass with only a small amount of material on show.

Thermal efficiency

There are many companies that manufacture and sell steel windows and doors that do not create their frames with a thermal break. As metal is a conductive material, lack of a thermal break leads to thermal bridging.

If the frame is cold on the outside the cold would be drawn into the house and can create condensation, and heat from within the home can be lost.

This will lead to possible damage to fabrics and furnishings that are in close proximity to the windows and can result in higher energy bills due to the thermal energy transfer.

All Sieger aluminium-framed glazing is manufactured in our state of the art facility with a modern thermal break that uses the latest in glazing technology.

With a thermal break installed the aluminium frames offer higher thermal insulation than can be achieved with the majority of steel frames.

For more information check out our technical advice article on thermal bridging and thermal breaks.

a full glazing package from sieger including grey framed aluminium bifold doors - casement windows - juliet balcony
aluminium steel look glazing with sliding patio doors and gable end windows with glazing bars

Many homeowners now desire aluminium glazing as a replacement for the existing old steel windows. That can be closely accredited to three main reasons for comparison.

Firstly, the cost-effectiveness of aluminium is a major deciding factor as the steel frames can cost more than double what you would have to pay out for aluminium frames without many advantages.

Secondly, the maintenance that steel requires is considerably more as steel can rust and corrode it must be treated every so often. Aluminium on the other hand requires minimal maintenance once it has been treated to protect the frames.

Lastly, the thermal efficiency of the two materials has a considerable difference as most steel frame manufacturers do not have a thermal break installed as standard. All Sieger systems are manufactured with a thermal break built-in which ensures high thermal efficiency is achieved.


If you have any questions about aluminium frames or our glazing solutions don’t hesitate together in touch with our team.

Our technical team are on hand to ensure you choose the right glazing for your project.

Call 01494 722 882 or email [email protected]

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