he surge in popularity for aluminium products last year will have gone unnoticed by very few in

the construction industry. It is predicted that aluminium specification is set for a 17-year high by 2020. Once the first choice product in the 1970s and 1980s, aluminium has seen a resurgence in the residential market over the past five years or so as bi-folding doors have become more popular. With their slimmer sightlines, some housebuilders are now also opting for aluminium windows to match.

While the demand for aluminium aesthet- ics increases, the availability of thermally efficient aluminium systems remains limited and expensive. This is where “warm aluminium” comes into play – a desire to combine aluminium aesthetics with the U-values expected from PVCu products. Warm aluminium is a hybrid product boasting the benefits of a PVCu core and the hardwearing exterior of aluminium. There are a few products available on the market which utilise a composite profile like this, although the approach varies from product to product.

Some companies manufacture PVCu profile as standard and apply an aluminium cladding onto finished windows or doors. Other suppliers adopt a more integrated approach, where the aluminium and PVCu materials are combined during the manufac- turing process. This gives the product more rigidity, and makes it more inherently an aluminium product, rather than an overclad plastic solution.

Using a hybrid aluminium/PVCu product

offers consumers aluminium aesthetics with the thermal capabilities of PVCu products. Only a few years ago, many of the most highly specified aluminium products avail- able advertised U-values between 1.76 and 1.94 W/m²K when using standard double glazing – meaning that many systems weren’t able to meet current Building Regulations.

During this same period, aluminium products have become the high-end choice for homeowners with a bit more money to spend. This is particularly evident in the popularity of aluminium bi-fold doors. Typically, aluminium bi-fold doors operate better than PVCu ones as they are stronger, and usually have slimmer sightlines. With this demand comes the need for housebuilders and developers to find future-proof products which meet energy efficiency requirements, while still allowing them to build contemporary homes with aluminium aesthetics at an affordable price. However, specifying standard aluminium products can be a headache for housebuilders. To take this back to basics, the problem with using aluminium through the building


As aluminium windows and doors continue to grow in popularity in the housing market, Bruce Manning of the Synseal Group takes a look at the advantages of warm aluminium products.

envelope is that it’s a highly conductive material – creating spaces which are prone to being too hot or too cold. PVCu has experi- enced many years of success not only because it’s cheaper to manufacture, but also because it has gone through a period of quite intense scrutiny when it comes to thermal efficiency.

Building Regulations for PVCu windows and doors are relatively strict, and systems companies competitively market their PVCu products with A+ energy ratings and below 1.0 W/m²K U-values.

In order to combat the poor thermal performance in aluminium, product design- ers need to use a form of thermal break. As PVCu is so thermally effective, it makes the most sense to use a multi-chambered PVCu core as a full width thermal break – and it enables the finished products to achieve U- values of 1.4 W/m²K double glazed and 1.0 W/m²K triple glazed for doors. While thermal performance is typically the main driver in the development of warm aluminium products, you also benefit from easier installation and lower material cost than pure aluminium.

There really are very few downsides to working with a warm aluminium product – particularly if you are used to working with PVCu. For developers, builders and installers, the PVCu core in a warm

aluminium system makes installation very simple because along the jambs where fixings are applied, the material is the same. Although the aluminium exterior won’t have as much flex as a solely PVCu product, this is an additional advantage in bi-fold, French and patio doors, because the frames and sashes are less likely to distort during use. Aluminium is also intrinsically stronger and more rigid than PVCu products, so the exterior on warm aluminium products provides additional security.

Perhaps the biggest impact that warm aluminium products have had though is the shorter lead times from around 10 weeks down to just four, generated from the benefits of the composite structure. This means dual colour can be achieved at the point of manufacture. Anthracite grey or black with a white interior is so common now, the supply chain needs to be able to respond to this demand on the same lead times as single colour specifications. So, will aluminium overtake PVCu once again as the preferred materials? Quite possibly – but 40 years on from its initial popularity, the products available have been reconsidered and re-engineered to offer the best of both worlds.

Bruce Manning is commercial new build manager at Synseal Group


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