The Importance of BTU Calculations for Your Central Heating System

Published: January 13, 2015 - by Anna Gillespie

Categories: For Homeowners

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The concept of central heating, to most, is something we generally expect and pay no real attention to. Until it goes wrong.

Whether you are undergoing a home move, a renovation or simply replacing a boiler or radiator, understanding and identifying the components of a central heating system can help you run your home more efficiently, save money and get the most out of your heating. That is why it is important to take BTU calculations into consideration. Broadly speaking, a BTU (British Thermal Unit) is a unit used to measure the amount of heat energy needed to raise the temperature of one pound of water by one degree Fahrenheit. When used as a unit for heating and cooling systems, it is measured per hour. If you correctly measure the BTU calculations, you will, therefore, find the most effective way of heating your home.

Why is it Important?

Not all radiators are created equally and if you get a radiator with the wrong level of BTU it may not heat your room adequately and efficiently. This then means higher bills and you may end up being reliant on other heating sources. By calculating the BTU’s required to heat a room you can sufficiently assume how many radiators will be needed to heat the room and what the output of those radiators needs to be in order to heat the room well.

Temperatures such as 21°C (70°F) for the lounge and 18 °C (64.4°F) for the bedroom are typically preferred temperatures. If your radiator has too high a level of BTU, you run the risk of wasting energy each time it is turned on. But, then again, if the BTU is too small you’ll never achieve the heat required to heat the room. Furthermore, your boiler could be going into overdrive trying to achieve the desired temperature.

Also, environmental factors need to be considered too. Determining the number of windows, type of floor, types of walls and whether or not there are outside walls can have a huge bearing on the amount of heat needed. Rooms with large windows, for example, take more energy to maintain at a comfortable temperature. Similarly, for rooms with high ceilings a larger radiator size is needed due the hot air rising.

How do I do it?

First, you need to determine the square footage of the room. Measure the length, width and height of the room. Multiply these three amounts. This should give you the volume of your home and dictates the amount of space that needs to be heated.

Next, work out the standard level of heating output in BTU to heat a room of this size. Multiply the volume by 153.

Then, you need to consider some of the main factors that can affect your BTU.

For example:

  • For high ceilings add 20% onto the figure.
  • For solid floors minus 10%
  • For upstairs bedrooms minus 25%.

It is also worth sizing the boiler to ensure that it will run efficiently alongside your radiators. Some suggest that getting a larger BTU-rated radiator is better than a lower one as the temperatures of individual radiators can simply be turned down if the room is too hot.

If math isn’t your thing, then use a heat output calculator that does all the BTU calculations for you. Check out this simple and effective calculator from BestHeating.

What Are the Calculations Based On?

Dan Holohan explains that this was due to Spanish flu, in around 1918 and actually had a huge effect. Because the flu was airborne, people were advised to keep their windows open and manuals from the 1920s urged for radiators and boilers to be manufactured based on the coldest day of the year, with the wind blowing and windows open.

What Other Options Are There to Control My Heating?

Temperature controls are definitely key elements when deciding on how much or how little heat you want. The thermostat on the front of your boiler will dictate how hot the water gets when it circulates around the house. Additionally, room thermostats and thermostatic radiator valves dictate how warm (or cool) you want each room to be, ensuring you are in control of your central heating and therefore your bills. 

Historically, heating systems were never linked with the influx of smart technology. Now, though, that has all changed. With the introduction of smart thermostats you are more in control of your home heating than ever, all done remotely from your smartphone or tablet.