The Ultimate Guide to UK Radiators March 21, 2024

The Ultimate Guide to UK Radiators

The ultimate guide to UK radiators. WarmZilla blogs.
UK Radiators Explained
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    The ultimate guide to UK radiators. WarmZilla blogs.

    According to a YouGov survey, only 16% of the UK population in 2023 has maintained the usual spending habits and can afford to do so during the Cost of Living Crisis.

    This forced adjustment in habitual spending has resulted in some new consumer behaviour. According to Citizens Advice, around 8 million UK citizens had to borrow money to pay for their energy bills, and over a million had to disconnect for extended periods over the first six months of 2023.

    As a UK citizen, this makes for bleak reading. But these statistics and figures give us insight on what changes you can make to understand how your radiator works and ultimately save money.

    By doing so, you can run it more effectively for longer and perform simple maintenance jobs, which have several benefits.

    Before we get ahead of ourselves, let’s go through the basics of how a radiator works.

    A Breakdown Of How Radiators Work

    Radiators work by transferring heat from a central source (think boiler) to the rest of your house.

    How radiators work in your home. Showing the functions of the boiler, radiators, distribution pipes and return pipes. WarmZilla Blogs.

    To understand how your home’s radiator transfers, you must learn these terms/ideas:

    What’s The Heating Source?

    As mentioned, your radiator is fed heat from a central heat-producing source. Various energy sources, such as gas, electricity, oil, etc fuel these heating sources.

    Most central heating systems (86%) in the UK run off gas. While the UK government is trying to phase out the country’s reliance on using gas, it’s unlikely to become a reality for many years.

    Now, let’s focus on transferring this heat.

    Heat Transfer

    Heat transfer occurs when hot water or steam flows from the central heating source through the system’s piping and valves. This heated liquid or gas flows into the radiator and transfers heat energy into the metal panels or fins.

    Think of the sides of a kettle that is boiling. As the water heats up, it transfers heat energy into the sides of the kettle.


    Once the heat energy has transferred to the metal panels or fins on your radiator, convection comes into play.

    Convection is the process where heat is distributed through a fluid or air.This is the reason why you feel warmth radiating from your radiator.

    This radiating warmth now affects the surrounding air.

    Air Circulation / Or Air Flow

    When the air surrounding your radiator is heated up, it becomes less dense than the colder air around it, which means the hot air rises above the cold air.

    This repeated and continuous circulation or flow of air where warmer is replaced by colder air is responsible for the distribution of warmth.

    Another way a radiator can develop heat is via radiation, which, through emitted infrared radiation, can heat objects and surfaces in a room.

    Now that we understand how heat is distributed from a radiator. How do you control the heat emitted from your radiator?

    Thermostat Control And Valves

    Usually, a thermostat controls your home’s heating system. Thermostats work by monitoring the temperature in a room and regulating the flow of hot water or steam via valves.

    There are different types of valves, including the following:

    Lockshield Valve

    The name refers to the fact that you can lock the valve, stopping the water flow. As a generalisation, you need to have a screwdriver to loosen this type of valve, and it is normally on the outlet side of the radiator.

    These valves allow you to balance the system to ensure appropriate heat in certain areas.

    Manual Valve

    A manual valve allows homeowners to adjust it via a dial or knob, which will give a flow-rate indication (increase or decrease). Manual valves can be fitted to inlet and outlet points on the radiator.

    The main bonus of having a manual valve fitted to your radiator is it allows complete control over your heating system. But for those not interested in manual labour.

    Thermostatic Radiator Valves (TRVs)

    Far more common nowadays, as installers have tended to fit TRVs as the go-to solution, these valves allow for automatic temperature adjustments.

    TRVs are fitted on inlet and outlet pipes and indicate the desired temperature on a dial. Simply turn the dial to the desired temperature, and it does the rest.

    There are now also options for smart TVRs, which allow the user to adjust the temperature remotely at any time. This is great for those moments when you’ve forgotten to switch the radiator off and are out and about.

    Now that we understand how a radiator (or a plumbed radiator - we will explain more now) works. Let’s talk about the different fuelled radiator options in your home.

    Types of Fuelled Radiators Used In The UK

    As with anything in life, there are multiple options of radiators to choose from. They come in all shapes, sizes, styles, and materials.

    But most radiators installed in UK homes can be categorised into plumbed, electric, or dual-fuel. Let’s look at the main differences between these three fuel types.

    Plumbed Radiators

    As the name suggests, a plumbed radiator uses the water supplied by the premise’s boiler. It is also the most common type of radiator used in UK homes.

    Replacing older radiator models with more efficient ones is a simple task, but does need to be done by a professional.

    Electric Radiators

    In 2021, some 301,035 units of electric radiators and heaters were sold in the UK. While this seems like a large number of units, the demand for electric radiators and heaters has decreased. Despite the fact that electric radiators have come on leaps and bounds in efficiency.

    Also, electric radiators need less maintenance and can be installed relatively easily. But unfortunately, it is still more expensive to run an electric heating system in the UK.

    According to price guides by Ofgem Energy Price Guarantee published for 1 January to 31 March 2024:

    Type of Radiator Energy Price per Unit
    Electricity 28.62p per kWh & 53.35p daily standing charge
    Gas 7.42p per kWh & 29.60p daily standing charge

    As we mentioned, there is a cost of living crisis in the UK, so the price difference might make you reconsider switching to an electrical radiator.

    But there is also a dual fuel system to talk about.

    Dual Fuel Radiator

    A dual-fuel radiator utilises two heating sources: plumbed and electrical. This means you can tap into the benefits of both systems.

    If you’re looking to heat a bathroom or kitchen area, you can use a plumbed system, while in sitting rooms or bedrooms, you can use the electrical heater. This means you’ll be able to cut down on piping.

    Now that we know the types of fuels, let’s focus on the materials.

    Radiator Material Types

    In the UK market, there are four radiator material types. These include:

    • Cast iron
    • Aluminium
    • Mild steel
    • Stainless steel

    All these materials have benefits and drawbacks, which means weighing up what is best for your needs.

    Cast Iron

    Older radiators were made from cast iron. In the past, the material's low melting point made it easy to manufacture radiators. The ease of using the material meant it was popular, and it also retains heat well and releases it slowly.

    The material, while heavy, helps to ensure that the radiator is strong, and a generalisation is that cast iron radiators are well made and created to last.

    However, cast iron radiators take a long time to warm up. If you’re expecting cold weather, plan for the pre-heating process. But once it has reached temperature, you can turn it off and enjoy the heat for a while.

    Reaching the optimum temperature will be an expensive exercise many would rather avoid.


    One of the more recently used radiator materials, Aluminium warms up the fastest. Aluminium radiators are known for their ability to heat a space quickly and efficiently. Also, compared to the other materials on this short list, aluminium radiators make roughly two to three times more heat.

    In addition, aluminium radiators are lighter and more thermally efficient. However, with these great benefits, aluminium radiators are not perfect

    While lightweight, aluminium radiators are more fragile than other materials. Also, aluminium will require a substantial cash investment.

    However, with fuel costs skyrocketing, it could be an investment for the future.

    Mild Steel

    Currently, mild steel radiators are the most common in UK homes. Mild steel is popular because it is inexpensive to produce and, thus, cheap to buy.

    Because mild steel is cheaper, there are more radiator options to select from, and because it is steel, it’s tough.

    However, mild steel is prone to rusting from the inside, which requires regular services. This potential risk of rust shortens the guarantees and warranties for mild steel radiators.

    But with a regular service, there should be nothing to worry about.

    Stainless Steel

    Stainless and mild steel share many of the same characteristics. Both options are strongly built, available in multiple designs, and will last if treated correctly. However, the main difference is that stainless steel is rust-resistant.

    Being rust-resistant means that stainless steel radiators have longer extended warranties and guarantees.

    However, stainless steel can actually rust if poorly treated, and it is more expensive. Even though they are rust-resistant, they will require regular services from a professional.

    Now that we’ve investigated the types of materials used to create radiators, it’s time to look at the different styles.

    Different Radiator Styles

    For those interested in the aesthetics and interior design of the home, knowing what radiator styles are available will be the most crucial aspect.

    It’s also worth mentioning that radiator styles will affect the unit's functionality.

    So, here are some radiator styles to consider:

    Conventional Radiators

    Conventional radiators are the most common type of radiator installed in UK central heating systems. Working by circulating warm water or steam through the unit, heat is transferred via convection, where the radiator's walls warm up, and excess warmth heats the cold air.

    Panel Radiators

    Similar to conventional radiators, these have a flat panel, as the name suggests. This makes them perfect for compact spaces. Also, you can order panel radiators in multiple configurations, such as single, double, or triple panel configurations.

    Towel Radiators

    Generally, towel radiators are found in bathrooms. Used to warm bath towels, these are usually a ladder structure made from stainless steel.

    Column Radiators

    When most people imagine a radiator, the image will likely be a column radiator. These will give any room a traditional look and feel. And because we live in the modern world, there’s a vast variety of sizes.

    Low Surface Temperature Radiators (LSTs)

    Usually, LSTs are installed in public spaces such as schools, hospitals, and other public places due to safety requirements. As the name suggests, LSTs provide heat with a reduced risk of burns.

    Skirting Board Radiators

    As the name would suggest, these are installed in the skirting boards of a room. This means that they are out of sight and a great space saver.

    But if you want complete discretion?

    Underfloor Heating

    Piping the heating system under the floor can provide even and efficient heat throughout the home.

    While these are all styles for radiators, what do types 10, 21, 11, and 22 mean when purchasing a radiator?

    Different Types of Panels

    When looking through radiator catalogs, you’ll see the terms Single Panel Radiators (Type 1-1), Double Panel Plus Radiators (Type 2-1), and Double Panel Radiators.

    Let’s break down each type of panel layout:

    Single Panel Radiators (Type 1-1)

    Single Panel Radiators or Type 1-1s have a single panel in the front of the unit with convection fins (which circulate the water from the boiler) fixed on the back. Type 1-1 radiators will produce around 1kW.

    As you can imagine, Type 1-1 is:

    • An economical radiator
    • Slim and easy to fit into smaller spaces
    • While smaller, produces an impressive amount of heat

    If you’re looking for a radiator to suit a medium-sized space, the Type 21 is for you.

    Double Panel Plus Radiators (Type 2-1)

    As the name would indicate, a double panel plus radiator has two glossy metal heating panels at the front and back of the unit. But between these panels is one layer of convection fins.

    The double panels mean that a Type 2-1 can channel the cold air more cleanly over the convection fins, producing more heat. Its designation as a Type 2-1 refers to having two panels and one set of convection fins.

    Usually, a Type 2-1 will generate roughly 1.5 kW of heat. Now that we’ve broken down what a Type 2-1 radiator is, we’d recommend installing them if you’re looking for:

    • A higher heat output than from your Type 1-1
    • Something more space-efficient than the following option (Type 2-2)
    • Efficient heating (it has the best balance)

    Double Panel Radiators (Type 2-2)

    Now that we understand the product designation code, it’s obvious that these radiators have two panels with two heating fins wedged in between.

    As you’d imagine, these radiators produce more heat and are better for larger rooms. A Type 2-2 radiator will require a large boiler to keep it going, producing up to 2.5kW of heating power.

    While we’ve been referring to the kW of heating power, all radiators will also display a British Thermal Units (BTUs) rating in the product's main headline.

    So, what are BTUs, and how do they affect your decision to purchase a radiator for a room in the home?

    What Are British Thermal Units (BTU)?

    British Thermal Units (BTU) are a measurement of heat energy. It was originally defined as measuring the amount of heat to raise the temperature of one pound of water by a single degree of Fahrenheit.

    Over the years, the scientific definition of a BTU has changed. But nowadays, BTUs give the consumer a specific idea of how many square feet the potential radiator can heat rather than vague generalisations about room sizes. This is regardless of whether the room is empty or a collection of kids beds.

    The higher the rating of BTU a radiator can put out, the more potential space it can heat. This means if you’re looking for a radiator for a smaller room, you’ll be looking for a unit with a lower BTU rating.

    However, your BTU requirements are impacted by some factors, which are:

    Windows And Doors

    Your home’s capacity to reduce cold air flow from the outside, or convection transference of the cold, will impact the number of BTUs your room needs.

    If doors are well-insulated and windows are double-glazed, your heating source will not require a high number of BTU.

    The opposite situation, where doors are badly insulated and windows single-glazed, will result in your heating source requiring more BTU.

    Also, the size of the window and its area will affect your BTU requirements.

    Number of Outside Walls

    If the room you’re planning on heating is in the center of the home or has several walls between it and the outside, your BTU requirements will be lower.

    Room Size

    We already mentioned that the larger the floor space, the more BTU you’ll need to heat it.

    Ground Or First Floor

    If the room is situated on the ground or first floor, this will also affect your requirements for BTU. Rooms on higher floors will be generally warmer as heat rises.

    Now that we understand what BTUs are, let’s focus on how to work out what radiator you need for your space via a BTU rating.

    Calculating BTU Requirements

    Calculating your BTU requirements is complicated.

    Several methods exist, but we suggest using an online calculator.

    With these tools, you can determine the number of radiators required to heat a space.

    Now that we’ve clarified what a BTU is and what BTU unit you’ll need for your home, you might want to know how to ensure you’re running your radiator as efficiently as possible.

    How To Run A Radiator Efficiently

    As we discussed at the top of this article, the UK is experiencing an energy and cost of living crisis. While the UK’s record-high energy price of £363.70 in August 2022 has dropped, many are recovering from this financially turbulent time.

    Which means running radiators efficiently is important. You can do several simple tasks to ensure they operate at their best.

    Balance Your Radiator

    Achieving balance in your heating system involves making sure that there is a consistent flow of hot water circulating through the system at an even rate. This will ensure your radiators are optimised for efficiency.

    Tools you’ll need for this job are:

    • Radiator bleed key
    • A spanner (can be any tool that can loosen a bolt)
    • A screwdriver
    • A digital thermometer

    If you can’t find a digital thermometer or an old-school thermometer, you can feel the heat with your hands. Just be careful not to burn yourself.

    To balance your system, make sure to follow these steps:


    Start balancing your radiators by turning off the heating system or boiler. When the system is off, allow the radiators to cool down.

    Understanding Valves

    We’ve mentioned there are a few different valves you can expect to find attached to your radiator. Make sure that they are open. Typically, TRVs are on the radiator inlet pipes, while lockshield valves are on the outlets.

    Also, if you’re unsure what setting to have your TRVs on, ensure they are set at their highest setting.

    Remember, if you’re unsure what valve types you’re dealing with on your system, you can scroll back to that section in this blog.

    System Evaluation

    With all valves open, switch on the system and observe how each radiator heats up. Note the sequence of hot water distribution, as the closest radiator to the boiler will warm up first.

    If your home has multiple rooms, ask for help checking the radiator heating order. Once you know the order, turn off the heating system and let it cool completely before making precise adjustments.

    Which brings us back to step one.

    Initial Adjustment

    Restart the heating and begin with the first radiator. Close the lockshield valve and gradually reopen the valves to regulate the flow and temperature.

    Balancing the water flow going in and out will take time, so be patient. But when you’re ready, it’s time to monitor the temperature.

    Temperature Monitoring

    Once the radiator is warm, measure the temperature at the inlet and outlet valves. Adjust the lockshield valve until it reads 12°C lower than the inlet.

    When this has been completed, it’s time to repeat the process with all your home’s radiators.

    Moving further away from the boiler, you can expect to open lockshield valves more, ensuring a good, even heat distribution throughout the home.

    After you’ve adjusted your last radiator, you’ve officially balanced your system.

    It’s recommended that homeowners should have their radiators balanced once a year. By ensuring that the radiator is balanced regularly, you will prolong the unit's life and ensure it works efficiently.

    There are times that your radiator will need to be balanced immediately, which are:

    • When removing the radiator to paint the walls
    • After replacing the unit or valves
    • If you have to flush or cleanse your system* (we will get to this)
    • Something in your heating system has been replaced, like a boiler

    But what if your radiators still have cold spots towards the top and make a noise?

    Cold spots on radiators are common and can be fixed by bleeding your radiators. It’s a common misconception that balancing and bleeding a radiator are the same process.

    Also, ridding your radiators of cold spots will ensure that your heating system is running efficiently, and it’s an easy task.

    How To Bleed Your Radiator

    If there are cold spots at the top of your radiator, you will need to bleed it. This happens because there’s trapped air inside your radiator where the cold spot is.

    By bleeding your radiator, you release this trapped air. It is a simple task, and all you’ll need is:

    • A radiator key or flat-head screw (depending on your system)
    • A container for water
    • A few towels

    Before bleeding your system, make sure it is turned off and cooled down. Each radiator will have a bleed valve. These are usually located at the top of the radiator to allow the air to escape.

    The bleed valve will look like a small square-shaped valve with a central spindle. When you’re ready and sure where everything is, prep the area with your towel in case of a small spill.

    Use the radiator key or screwdriver to turn the bleed valve counterclockwise. Listen for a hissing sound as air escapes, and have a container and cloth ready to catch any water.

    Keep the valve open until water flows steadily, then close it. Avoid overtightening to prevent future issues.

    After bleeding, ensure the system pressure is correct. Once this is done, you’ve officially bled your radiator.

    But what if there are still cold spots? Or, while balancing your radiators, you discovered a faulty TRV?

    Well, now it’s time to troubleshoot some common radiator issues.

    Common UK Radiator Issues

    Balancing your radiator will fix several issues, such as:

    • Radiators not working downstairs
    • Cold spots at the top of your radiator
    • Radiator noises

    But sometimes, when balancing your radiators, you encounter a stuck valve. Fixing this is a simple task you can do yourself.

    Checking Your TRV Valves

    If one of your radiators is not warming up, it could have something to do with a faulty valve.

    The most common valve in modern UK homes is a TRV, which controls the flow of hot water automatically with temperature-sensitive membranes. But sometimes, these can get stuck.

    To check if this valve is stuck, turn off the heating system and wait for it to cool down. Remove the rotatable head on the TVR, allowing you to look at the raised pin underneath.

    This should allow you to push down the pin with your finger. If it doesn’t pop up or is not moving well, then you’re looking at a problem valve.

    The simplest solution is to apply WD40 to the pin and use a small pair of pliers or mole grip to work the pin up and down. Doing this gently a few times should make it move easier. But be careful, as too much pressure can break it.

    If this hasn’t worked, we’d recommend calling in a professional heating engineer.

    If you’re struggling with cold spots at the bottom of your radiator, you will most likely have a sludge issue.

    Cold Spot At The Bottom Of Your Radiator?

    When there are cold spots at the bottom of the radiator, and the top is hot, it’s most likely caused by sludge. The sludge inside your radiator is a build-up of metallic elements and dirty system water.

    Over time, all systems will gather a bit of sludge, but if not addressed, it can build up at the bottom of your radiator, causing that cold spot.

    Another factor contributing to sludge is limescale, a common occurrence in areas with hard water. Over time, the minerals in the hard water can solidify and become limescale, which will eventually mix with the sludge gathering at the bottom of the radiator.

    But how can you solve this problem?

    Chemical Flush

    A chemical flush is exactly what it sounds like: purging your system with specialised chemicals to eliminate stubborn sludge buildup

    These chemicals break down the sludge, allowing it to be flushed out of the system with water.

    Following this flush, a chemical inhibitor is introduced to prevent future corrosion.

    But if this doesn’t work, you must call a heating engineer to conduct a powerflush.

    A powerflush requires a powerflushing machine, which applies a high-pressure water spray and chemicals to dislodge stubborn sludge.

    Beware that this is a vigorous procedure and can rattle loose pipes. Make sure to call a trusted heating engineer from the Gas Safe register to quote on it, as doing this yourself is not recommended.

    To prevent sludge from building up in your radiators, you can install specialised filters that are magnetic, and you can also add a scale reducer and inhibitor to the system regularly.

    If you haven’t found the answer related to your radiator question, we’d recommend reaching out to one of our agents. Simply click on the speech bubble in the bottom right-hand corner of the screen.