Aluminium radiators are increasingly seen as an alternative to the steel and cast iron radiators we are more familiar with. However, as a relatively new offering in the UK, radiator retailers are often asked the following questions:
• What are the benefits of aluminium radiators?
• What is the difference between aluminium and steel or cast iron radiators?
• Is there anything I need to be aware of when buying aluminium radiators?
The benefits of using aluminium to make radiators
Aluminium's physical properties make it a perfect material to construct a radiator from. It offers the following positive characteristics:
• Recyclable - as aluminium can easily be re-worked, recycled aluminium is widely used in every day products including radiators;
• Inexpensive - using recycled aluminium keeps production costs down;
• Light-weight - this makes transportation and installation easier and, consequently, cheaper;
• Long guarantee periods - aluminium radiators come with guarantees of up to 10 years as this material has a protective film of surface oxide making it naturally resistant to corrosion, although, other inputs can cause a risk of corrosion. See below for more information*;
• Quick to react or "thermally conductive" - aluminium ensures rapid heat transfer from the water within the radiator to the air in the room. In practical terms this means that the radiators only need to be switched on just before the room is needed. On the flip side, aluminium cools down equally quickly unlike cast iron which retains heat for hours.
• Variety of shapes and styles - aluminium is relatively soft, yet durable and has a high "ductile strength" meaning it can be stretched or "extruded" into long strips. Therefore aluminium is often used in vertical radiator models and is commonly used for contemporary style "feature radiators"; and
• "Sectional" options - the "extrusion" process means that uniformly shaped sections can be formed and radiators can be of "sectional" construction. A sectional aluminium radiator is assembled by joining any number of sections together to create the desired width; this allows for a vast selection of widths and means that radiators can be easily sized to fit onto existing pipework. The same sectional construction method is used for cast iron and some steel radiators. Scope for large radiators means that huge heat outputs can be achieved.
Comparing aluminium to steel and cast iron
There is not one material that is better than the other; there are pros and cons for each. Your choice will depend on your particular circumstances and specification.
• Price - there is a common misconception that the cost of a radiator is entirely dependent on the material it is made from but there are so many other factors at play.
• Weight - Aluminium is light-weight whereas cast iron is heavy and steel sits somewhere between the two.
• Guarantee periods - aluminium radiators usually come with 10 year manufacturer's guarantee but so do cast iron radiators. Steel tend to come with less at 5 years as steel is more prone to corrosion, though if the radiator is installed and maintained properly, this should not be a problem.
• Speed of reaction - aluminium heats up quickly, but then cools down quickly whereas cast iron takes longer to heat up, and retains the heat for longer after switch off. Steel sits somewhere in the middle.
• Shapes and sizes - aluminium is relatively more ductile and malleable than steel and cast iron.
*Prevention against corrosion
In order to comply with your radiator guarantee, your radiator must be installed in accordance with BS5449, section five commissioning, which is a process your installer should be fully aware of. This means on completion of installation, the system should be properly flushed and filled to remove debris and minimize the presence of solid particles and chemical residue that may cause corrosion and damage within the system.
Any radiator (except those on a secondary hot water system) must be used in conjunction with a suitable corrosion inhibitor.
Corrosion inhibitor should be used in accordance with the manufacturer's instructions and recommendations and should take into account the particular metals within the system. Corrosion inhibitors are available from most plumbers' merchants and DIY stores.