Guide written by:
Anne, Painter, Cambridge
The main factors to take into account when choosing a central heating radiator are:
Material - choose between:
cast iron: heavy, retains heat well, slow to heat up;
aluminium: lighter than cast iron, retains heat very well, quicker to heat up;
steel: lightweight, retains heat moderately well and quick to heat up.
Power - calculate according to:
surface (L x W) or volume (L x W x H) of the room you want to heat;
quality of your insulation: 0.1 kW / m² or 0.04 kW / m3 for well-insulated homes and 0.6 kW /m² or 0.024 kW / m3 for moderately well-insulated homes;
the type of thermal comfort you're after.
a low temperature heating system: radiator limited to 50°C for greater thermal comfort;
high heat output: radiator can heat up to 90°C; more energy-intensive but faster to heat up.
Shape, size and colour - according to your home layout and personal preferences:
skirting board heating to gain space;
underfloor heating (convection heating);
extra slimline horizontal or vertical radiator to save space.
CE standard (European standards).
BS standard (British standard).
EN 442: defines the thermal output of central heating radiators.
Warranty: 5, 10, 15 or 20 years.
Unlike electric heaters, central heating radiators are designed to be connected to your boiler, but can also be connected to a heat pump or solar heating system. Central heating radiators release heat through the water (or heat transfer fluid) contained within them.
These radiators are connected to the boiler and to each other through two pipes:
one pipe takes the hot water to the radiators;
another pipe collects cooled water from each of the radiators and sends it back through the boiler to be heated once more.
Central heating radiators release part of their heat through radiation. However, the majority of radiators release most of their heat through convection. The frame of these radiators is hollow which allows the thermal transfer liquid to travel through the unit. Their iconic shape – complete with pipes and fins – allows for more effective thermal transfer.
Low temperature radiators have a large heating surface which allows them to release a great amount of heat using cooler water. They are generally designed to be connected to a low temperature boiler or condensing boiler. This makes them much safer for homes with children and allows you to save a fair amount of energy.
Some models are even designed to heat by convection only; these models are known as convection radiators. These radiators tend to be used in underfloor heating or as skirting board heating systems. The heat is released by the natural movement of the air which flows upwards through the unit. These radiators work great as part of a low temperature heating system alongside a heat pump.
It'll come as no surprise to hear that the difference between these models comes down to water temperature. While both types of radiator perform the same basic function, the water temperature is able to reach up to 90°C for a traditional radiator and is limited to just 50°C for a low temperature heating system. In terms of energy consumption, low temperature heating systems are more economical as they require less effort from the boiler. However, these radiators do require a larger heating surface meaning they are a bit bulkier. For the most efficient system, it's a good idea to combine your low temperature radiator with a low temperature heating (LTH) boiler or a heat pump (which is designed to increase temperatures). Traditional radiators will heat up more quickly and stay warm for longer. However, they do consume more energy.
The amount of power you need to heat a home depends on the volume of the space you want to heat, the quality of your insulation and where your home is (in terms of region and altitude). The power output of a radiator is given in watts (W) or kilowatts (kW); remember: 1 kW = 1000 W. You can use the surface and volume of your rooms to calculate how much power you need from your central heating radiators.
The surface of your space is measured in m² and can be calculated by multiplying the length and width of a room. The volume of a room is indicated in m3 and is calculated by multiplying the surface of the room by the height. It's worth bearing in mind that the average room measures about 2.5 metres in height.
Homes can be categorised according to the quality of their insulation and the amount of resulting heat losses.
An older home is likely to have greater heat losses caused by inferior insulation. A home with average to good insulation will require a heat output of around 100 W per m² or 0.04 kW per m3. A room measuring 30 m², or 45 m3, will therefore require a central heating radiator with a heat output of 3 kW (30 x 100 or 45 x 0.04).
Newer homes tend to be very well insulated and don't lose a lot of heat. These homes only need about 60 W per m² or 0.024 kW per m3. In a very well-insulated room measuring 30 m², a radiator with a heat output of 1.8 kW will be largely sufficient (30 x 60 or 45 x 0.024).
The quality of heat transfer depends mainly on the temperature difference between the outer surface of the radiator and the surrounding air. It is therefore essential to pick the right type of material. Central heating radiators come in three main materials, each with different thermal properties.
Cast iron radiators retain heat very well as they have a great capacity for heat storage. However, they do take a long time to heat up. These radiators are strong but tend to be bulky, making them tricky to install (due to their weight), and are expensive.
Aluminium central heating radiators heat up very quickly and take a long time to cool down. They are therefore ideal for well-insulated homes. However, these radiators cannot be used in conjunction with radiators made from different metals due to the risk of corrosion. They tend to feature a fairly traditional design.
As they tend to feature thin fins and therefore less water than other radiators, steel radiators do not retain heat as well as cast iron radiators. They heat up quickly but also cool down at the same rate, meaning they can only really be used in well-insulated rooms or rooms that aren't used on a regular basis. That said, steel radiators come in a wide range of designs, sizes and colours.
In recent years, central heating radiators have taken on a whole range of new designs. From the most traditional to the most stylish radiator, there's a model out there to suit everyone! Of course, the most important factor in choosing a radiator is where it will be installed; the location of the radiator will pretty much dictate its shape and size.
Vertical or horizontal radiators are designed to be mounted on the wall; the design of the pipes differs accordingly. The amount of space these models take up will depend on their overall dimensions.
Skirting board heating systems are discreet but trickier to install. These are generally low temperature heating systems making them a safe option for those with children; these models are ideal for making the most of a smaller space.
Attractive and efficient, slimline radiators are designed to blend into your home. They can also be used to add a modern twist to your interior.
Gone are the days when radiators had to be basic 'accordion'-shaped units; these days, designer radiators can be seen as decorative items in themselves! From mirror effects and different colours to stainless steel, glass and various streamlined or original shapes... you're sure to find the perfect radiator for you – you just need to set aside the right kind of budget!
If you're looking to heat a particularly small or large space, it is possible to get a custom-made radiator. Bear in mind that it's usually more effective to install two small radiators rather than one big one for better heat distribution. Ideally, a radiator should be used to cover about 15 m².
It's a good idea to fit your radiators with a thermostatic valve; this will allow you to adjust your temperature for even greater comfort.
Clean your radiators using an angled brush to remove dust with ease. Never use any harsh chemicals.
Bleed your radiators at the start and end of winter to ensure they are working as efficiently as possible.
Guide written by:
Anne, Painter, Cambridge
After 8 years of trade, I turned professional: I trained myself to be a painter and carpet fitter, either on my own or with 16 year old comrades. 9 months later, following vocational training, I created my company. I’m a self-taught DIYer and decoration enthusiast, I love to find and restore furniture and to create unique decoration pieces. I completed the renovation of my sister’s house with my niece: electrics, tiling, plasterboard...we did it all. And today, if I can share my experience I'm happy to do it. Good Luck.