Well-maintained, high-quality aluminium and composite windows both have a lifespan of around 50 years, making them extremely worthwhile investments for large-scale window projects. However, which option is most suitable to the needs of your project?
In this article, we look at the differences between aluminium and composite windows in terms of sustainability, thermal performance, maintenance, and whole-life costs, to help you make an informed choice.
1. Thermal Performance
- Aluminium windows: Aluminium windows are thermally broken to reduce heat transfer. This allows commercial aluminium windows to not just meet the modern energy efficiency standards of Document L, and can often exceed it, whilst retaining a sleek design with durability. There has been a vast improvement over the last 10 years in the energy efficiency of aluminium windows and there are now many Passiv-haus options available which have the maximum thermal insulation properties.
- Composite Windows: They are an excellent choice for thermal performance due to their mixed-material construction. The internal layers, made of uPVC or timber, provide excellent insulation, helping maintain consistent indoor temperatures throughout your building, and delivering good energy savings.
Key takeaway: Although composite windows are well known for their excellent thermal properties thanks to the timber contained within them, similar performance can be achieved with commercial aluminium windows. A comparison between aluminium and composite windows can be found below when using the same sized window, glass specification and insulated panel. Composite windows are still marginally better in thermal efficiency.
- Composite Window: U Value 1.13 W/m2K
- Aluminium Window: U Value 1.2 W/m2K
2. Weight
- Aluminium windows: Aluminium is an exceptionally strong yet lightweight metal, making it the material of choice for many large-scale curtain walling systems. The low weight ratio reduces strain on the building’s foundation and structure, while its strength enables it to support expansive glass panels. Thanks to their lighter weight, commercial aluminium windows are often faster and easier to install, particularly in large curtain walling systems. This can reduce the time and labour required on-site, helping you to control project costs.
- Composite windows: The additional weight of these windows can complicate installation, especially in projects that require crane equipment or manual handling at height, which can have implications for project timeframes and costs. In tall buildings where every kilogram of extra weight added to the façade can increase pressure at the foundational level, composite windows may require additional reinforcement of the building’s structural framework.
Key takeaway: Aluminium windows are lighter which can help reduce costs of the structure and bracketry.
3. Sustainability
- Aluminium windows: Aluminium is one of the most recyclable materials used in the construction sector, capable of being recycled indefinitely without degrading in quality. Aluminium windows can be repurposed or processed into various new products when no longer functional, maximising their sustainability value.
- Composite windows: Recycling composite windows can be a challenge due to the multiple components made from a wide array of materials contained within them. Recycling requires the separation of the timber or uPVC from the aluminium. Timber can generally only be repurposed once and be made into wood chippings or sawdust whilst uPVC can be recycled many times.
Key takeaway: With sustainability at the forefront of many business decisions, it is important to indicate that aluminium is 100% recyclable. In fact, recycling aluminium windows can save 95% of the energy required to make new aluminium.
4. Costs
We ran a study where we priced the below window in both Timber-alu composite and Aluminium with the same glass specification and insulated panel and found that there was approximately a 5% cost reduction for aluminium vs composite windows at the point of sale. It is worth taking into account the whole life costings noted below.
- Aluminium windows: Commercial aluminium windows are an attractive choice for high-spec glazing projects as they also require less maintenance than composite windows, and do not rust, or warp. Having a long lifespan and minimal environmental and disposal costs, aluminium windows deliver superior whole-life value.
- Composite windows: The principal savings come from their excellent thermal efficiency which can decrease energy costs across the life of the building. Ongoing maintenance will also be more demanding, as timber-based components need to be repainted or resealed every 1 to 5 years (system dependent) to keep their appearance and weatherproofing ability.
Key takeaway: Commercial aluminium windows are around 5% more expensive at the point of sale and have very little maintenance cost over their lifetime however composite windows are around 5% cheaper at the point of sale but have extensive maintenance costs to maintain performance over their lifetime.
5. Options – Colours And Ironmongery
As with all windows currently on the market, there are many choices available for each option. Aluminium-clad Timber and UPVC composite windows typically come white internally but with aluminium windows, the standard would be for them to come the same colour internally as externally. There are many more colour combinations for Aluminium due to the ability for both the internal and external faces to be powder-coated or anodised vs only the external face of the composite window can be powder-coated or anodised.
Both options have many different options regarding ironmongery and handle with features such as monkey-tail handles and easy-clean hinges. To explore these options, as these vary between systems, if you have specific requirements, it is better to talk to us directly.
6. Size Limitations: Aluminium vs Composite Windows
When comparing aluminium vs composite windows, their sizes can differ due to differences in material strength. Here's how they compare:
- Aluminium windows: Are inherently stronger than composite windows; they are lighter and have a narrower frame depth of 65-90mm. An aluminium top hung open-out window can reach 2.5m x 2.5m with the right system and glass configuration. Aluminium windows are capable of achieving large sizes to maximise light into any property.
- Composite windows: These are heavier than aluminium windows and have a wider frame depth of around 150mm due to their composite structure which is why they offer great thermal performance. A composite top-hung window can achieve sizes of 1800mm wide and 1500mm when paired with the right glass specification.
Find Out More About Our Recent Projects
More information about the relative benefits of aluminium vs composite windows in different applications can be found on our recent projects page. Feel free to get in touch to find out more about any of these projects, or to discuss the best solution for your application.
