Saffet Kalender, Director at AEON by Pitacs, explains why it’s important to get the balance between cost, design, and efficiency of radiators right to ensure satisfied customers.

To create a standout product, designers need to get the optimum balance of: low water content, wet surface and convector area, material, water circulation, working pressure, build quality, aesthetics, finish quality, and price. We should constantly strive to both manufacture and specify products that achieve high efficiency and represent good value to the end-user. As an installer, here’s what to look for when evaluating the potential of a new radiator design for your customers.

Low water content

Less water going through the radiators optimises efficiency, saving on energy and cost, while also allowing for the specification of a smaller central heating system. We still see strong consumer demand for Victorian-inspired, column designs that evoke the old cast iron models, to complement a traditional interior or help to create a vintage-industrial look. However, these designs feature wide tubes which require a much higher water volume and have to compromise on energy efficiency. 

Ultra-slim profile radiators, on the other hand, are on-trend for the modern interior. They also offer the benefit of exposing more of the wall behind the radiator, allowing colour or texture to show through. However, this aesthetic can also weigh down on efficiency. A small internal diameter for water flow is optimal but, when it becomes too small, the water will not pass through easily, compromising circulation and causing pressure to drop. In this situation, the heating system will slow down or fail completely, similar to the result when the pipework used to plumb the radiator is too narrow.

Surface area and circulation

The greater the wet surface area, the more effectively a radiator will transmit heat. Square or rectangular shaped radiator rungs will give a better output compared to round tube cross-sections, due to their greater surface area across the same dimensions. 

Tube-in-tube designs further increase this efficiency; building round section tubes inside larger square section outer tubes increases the wet surface by about 40%, increasing the heat output by almost that much as well. Or, if a smaller size is desired, tube-in-tube designs can achieve the same heat output with a product that is 40% smaller in its dimensions. Of course, this size reduction is only possible to a certain point before circulation is compromised.

Speed and area of circulation are other significant issues in the search for optimum efficiency. A fast circulation is preferable so that heat is not lost before the water reaches the radiators however, once there, the water should circulate everywhere through the radiator with no ‘dead spots’. The superior circulation, larger external surface area, and internal wet surface area of the tube-in-tube design allows the radiator to transfer its heat more effectively to the room. 


The choice of material largely determines the cost of a designer radiator. Mild steel is a popular choice for panel radiators produced in bulk quantity for commercial and residential use, and increasingly allows manufacturers to offer items with designer aesthetics at budget prices, finished in chrome plating or paint. While chrome finishes have the advantage of complementing a range of themes and interiors, custom paints give the consumer the option of truly integrating their heating solution with their interior design, matching colours and tones exactly with other pieces in the room.

Colour finishes are certainly a major trend for 2020, but choosing a paint finish should not be an excuse to cut cost and select a budget material. In as little as six months after installation, a mild steel towel rail can start to flake or discolour from corrosion.

This deterioration usually begins near the valves, where paint or chrome plating is thin. In comparison, stainless steel won’t suffer flaking or discolouration, whether painted, brushed, or polished. 

Stainless steel is also a more efficient heat conductor than its mild steel equivalent. However, aluminium performs even better. Aluminium radiators both emit heat and respond to changes in water temperature quickly, which gives the consumer greater control over their environment. 

Being corrosion-resistant, aluminium also avoids the pitfalls of discolouration and flaking when painted or plated and, furthermore, the material is lighter than steel, which can make installation easier. 


The challenge is not limited to material; manufacturing and labour also impact cost. Producing an equivalent heat output on a smaller scale is ideal for a small space that needs a high output, such as a bathroom. However, the extra material required for the inner tube and the extra labour required to manufacture and weld it also increases the cost. A less expensive version of the square tube-in-tube design is tubes with a rectangular cross section; using less material, so less cost, but resulting in reduced heat output. 

As an installer, and key influencer for your customer, it is perhaps most important to call out the features and factors that the consumer can’t see when they consider a potential radiator purchase. The customer knows their own aesthetic preference; it falls to the designer to balance that aesthetic demand with the practical requirements of an efficient heating solution.