What Size Radiator Do I Need?

As Product Manager for Plumbing and Heating at BestBathrooms.com I am often asked what size radiator is best for a room. My answer is that it depends on two factors:
1.       The temperature that you want the radiator to be capable of maintaining.
2.       The heat loss from the room.

The temperature that you want in a particular room is a matter of personal preference, but the ideal temperatures for the rooms in your house are generally agreed to be:

  • Lounge               21°C7539_image
  • Dining Room      21°C
  • Kitchen               16°C
  • Bedroom             15°C
  • Bathroom            23°C
  • Stairs & Hall       18°C

Calculating the heat loss from a room is a complex business, as it depends on a large number of factors: size of room, the number of doors, the number and size of windows, the type of window, the number of outside walls, the material used in the construction of the walls, what is beneath the floor and above the ceiling, the amount of insulation; to name but a few. So, the description of each radiator in the BestBathrooms.com collection comes with a handy BTU calculator that takes all these factors into consideration and gives you the approximate output that the room needs.

BTUs (British Thermal Units per Hour) are a measure of the heat output of a radiator, which can also be measured in Watts. (There are about 3.5 Watts to 1 BTU.) If you install a radiator that is too big, the central heating system will overshoot the desired temperature and be less economical to run but, if it’s too small, the room will be colder than you want.

You will be lucky if the output of any radiator exactly matches the output you need for that room, so choose the first size of radiator above the output indicated.  Also, if it is a big room, you may want to install more than one radiator, to reduce the chance of ‘cold spots’.

Obviously, the calculations are approximate, but should give you a good idea of the size of radiator you need for a room. If you are engaging a plumber to install the radiator, he will be able to check your calculations and give further advice, if necessary.

If you have any more questions about BestBathrooms.com’s plumbing and heating products, their application and installation, please do not hesitate to contact me via this blog.

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