Radiators are now available in a huge range of models including contemporary, designer and traditional styles with each coming in its own range of finishes, from the whitest whites to outrageous oranges and gleaming chrome. Customers demand not just comfort but a stylish product to add to their interior décor, therefore heat output as well as design and finish are all critical when it comes to choosing a heating product.
However, when it comes to heat outputs, customers can find it all rather confusing. One reason is that the heat output can vary depending on purely the finish.
For example, a contemporary style design, may come in white, black or chrome. You would think that in the same size, they would all give the same heat output, but this is not the case. Instead the white and black models give out 20% more heat output than the chrome version. Chrome versions will always give out less heat (up to 30% less) than a painted equivalent.
So why do chrome radiators give out less heat than painted ones?
There are 3 key reasons why chrome models are not able to radiate as much heat out:
1. Firstly, this is down to the scientific phenomenon known as "surface emissivity". Chrome has a low emissivity value; this means that chrome tends to trap heat and it is difficult for it to emit or radiate heat. This explains why the seatbelt buckle in your car gets so hot on a sunny day. Although this may not make them ideal for "radiators", chrome does provide an excellent material for drying towels on.
2. Chrome is coating applied on top of another metal, usually mild steel or brass. This means that the heat has to penetrate through 2 layers of metal; and
3. Chrome is as shiny on the inside as it is on the outside meaning it reflects heat back in on itself reducing the amount it can radiate; it has an effect similar to the space blankets you see wrapped around long distance athletes after a race.
10 years ago, a chromium or chrome finish was the most popular finish option, but increasingly there is a movement away from chrome because of the lesser heat outputs. Now customers often opt for a polished stainless steel finish instead as this alternative option is very similar in appearance to chrome but, as it is bare metal rather than a coating, it is better at "radiating" heat.
There is also some difference in emissivity between not just finishes but also even colours. However the industry has agreed that this difference is negligible in practice and advertising heat outputs for every shade would over-complicate the decision for the consumer. Also manufacturers would require highly accurate, sophisticated and, consequently, expensive measuring apparatus to quantify the difference adding unnecessary costs.
Therefore models finished in white and other "painted" or powder coated finishes are always advertised as the same.
Bear in mind that retailers also may advertise the same products in the same finish with different heat outputs due to the variation in measuring standards used in Britain versus Europe. For more information on variations in heat outputs see our article "Different companies sometimes state different heat outputs for the same radiators, why?"