THE HEAT IS ON – Why powder coated radiators have a higher heat output than metal finish radiators
When you’re looking for a radiator, you want to know two things. How much heat will it give me and what’s it going to look like? If you choose an Eskimo radiator, and you really should, then you’ll get the answers you need and feel a whole lot of joy. High heat outputs that promote cost, and energy efficiency. Stunning finishes and beautiful architectural forms. Perfect. However you’ve got a budget that needs to meet a heat requirement so sometimes selecting a powder coat colour can be a helpful option, when it comes to finish. And you’re not being ‘boring’ either. Not only are their price tags lower due to process and materials, but colour radiators can also often give up to 30% higher heat outputs. Nothing boring about that. Of course, patinated brass or copper. Concrete, Bamboo or Supermirror finishes are stunning statement pieces. But in our experience, and one of the reasons that we will always present colour options too, colour radiators have the power to blend and ‘sooth’ a space and an ability to enhance incredibly beautiful lines within a well thought out interior.
Which leads us seamlessly to the other kind of power that you definitely want from your radiator. Why does a radiator in a powder coated colour finish have a higher heat output than your ‘fancier’ metal / reflective finishes?
The physics behind it is all related to something called surface emissivity. This is the ability of a surface to emit radiant heat. Radiant heat is when the heating system supplies heat directly to the room through the surface. So in our case through a front fascia or a module. Radiant Heat accounts for up to 20% of the heat output of a radiator. The rest being made up of convected heat. Convective heat transfer, often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. So in the UK, that’s water through our central heating system. How much radiant and convection heat you feel is entirely dependent on the surface finish characteristics of the radiator.
Emissivity is measured on a scale of 0 (least emissive) to 1 (most emissive). The perfect surface for radiating heat is a very matt black surface (measuring close to 1), the worst surface is any highly polished surface which will measure something like 0.01. Emissivity is effected at the microscopic scale in terms of the surface finish, and powder coating provides a microscopically matt surface even when using gloss powders, hence white gloss powder coat has a surface emissivity of 0.9, not far off matt black, which is why we don’t change the heat output for the different gloss levels or colours. Polished aluminium however has an emissivity of 0.02 meaning that it radiates very little heat at all, delivering almost exclusively convected heat, hence the 18% de-rating below our powder coat outputs.
You’ll note that some manufacturers don’t de-rate their polished products – this means they haven’t tested them as surface emissivity is a matter of physics and cannot be avoided. Either their polished product is over-rated (most likely) or their powder coat product is underrated. Also, chrome surfaces should always be de-rated below powder coat since all parts that are chrome plated are polished first. With our RON radiators in Polished aluminium or Matt aluminium finish, we took a decision to rate them the same. Technically Matt aluminium would have a higher output than a Polished aluminium. But as it’s polished before the anodising process, we wanted to under estimate its heat output to be on the safe side and give you an as accurate and as honest figure as possible.
One of the things to note with a mirror polished surface, because it doesn’t emit radiant heat, is that you won’t feel the heat from a distance, not until you touch it. Conversely you’ll be able to feel the heat from a powder coated radiator at a distance of several metres. This is particularly important in rooms with very high ceilings where a balance between convected and radiant heat is important, especially before the room warms up, since a proportion of radiant heat will operate directly on the user of a room before the air temperature has reached comfortable levels.
Like any decision on a finish, colour is an incredibly personal choice. Colour can be used to blend and tone, pop or accent. Be quiet or be loud. We can colour match to any paint. There is a vast variety of RAL reference colours to choose from. You can have whatever you want. So bathe in colour. Feel the heat. Let Eskimo and physics make your World complete.