Electric Underfloor Heating - What You Need to Know

It is a good idea to know all of your options when it comes to installing underfloor heating in your home or workplace. With an electric system, you will benefit from its convenience, simple installation process and quick heating time. Here is everything you need to know about electric underfloor heating. 

What is underfloor heating?

As a way of replacing radiators, underfloor heating works as the main source of heat in a property by heating up your floor. There are 2 types of underfloor heating: electric systems, which use electrical wires or mats to pump heat; and wet/water systems, where pipes are connected to your property’s boiler through a manifold and water is distributed along underfloor pipes. Below is an overview of each underfloor heating type. 

Wet/water underfloor heating

• Cheaper running costs compared to electric systems.
• A better choice for larger rooms and areas.
• Air source heat pumps can be installed to minimise energy use.
• A cheaper option for new build properties. 
• More options for control via a smartphone or tablet.

Electric underfloor heating

• Scope to choose wattage outputs for different rooms.
• Simple to install in your property.
• Floor height will only rise by 3mm. 
• An effective choice for smaller spaces such as bathrooms and kitchens.
• Can be added to older properties with minimal disruption. 

What is electric underfloor heating?

An electric underfloor heating system is made from a combination of either underfloor heating mats or wires under the flooring. It is a great alternative to traditional radiators and, on average, electrical underfloor heating systems run on a temperature range between 25°C - 31°C. This also depends on the type of flooring you have. 

Electric underfloor heating can be bought in 2 different options.

1. Loose wires

A good solution for awkwardly shaped rooms, loose wires can be flexibly laid. But you must make sure that there is an even amount of space between the wires. If the wires are too close, this can disrupt the heat distribution across the floor. 

2. Mats

At regular intervals, a group of wires are attached to mats. The mats can be cut to size and are laid on a smooth and level surface. The flooring, whether it is tiles or carpet, is laid on top of this. Despite being an easier option for installation, mat-based electric underfloor heating is not suitable for irregular-shaped or small spaces - this might prove tricky to work around the wires. 

How does electric underfloor heating work?

Primarily used for bathrooms and kitchens, electric underfloor heating is laid on top of floor insulation which helps the heat to be transported upwards instead of down. A system is placed on top of either suspended timber or screed - made from cement and sand - which creates a completely flat surface. A thermostat will help you to control the temperature of your electric underfloor heating system. You can also pre-set the system to turn on and off at certain times. Some are also available to monitor from your smartphone. 

Systems are varied from 100W or 200W per sqm and there are a few factors to consider when choosing the right one for you, such as the shape and size of the room, the type of flooring, the insulation of the room and the condition of the floor below. 

Will you need planning permission?

In most circumstances, whether you want to install electric underfloor heating for tiles or underfloor heating for carpet floors, you will not need to get planning permission. But if the building is of historical significance or a listed property, you will need to get planning permission. Visit the government’s Planning Portal to check whether planning permission applies to you. 

Electric underfloor heating pros and cons

Advantages of electric underfloor heating

Installing an electric underfloor heating system will bring a range of benefits to your property or place of work. Here are the main advantages to consider.

1. Low installation cost - particularly for electric underfloor heating mats, it is likely you will be able to do this yourself without the help of a professional. This will save you money on labour costs. For context, the cost of installing wet underfloor heating, as an alternative, could be around £300 per day. 
   
2. Quick heat - if you only want a short burst of heat, an electric system heats up quicker than its water counterpart. Also, with an electric system, the heat is transported upwards from the floor. This is more effective than a traditional radiator system where you are likely to get cold spots. 
   
3. Zero maintenance - an electric system is maintenance-free once it has been installed compared to a wet underfloor heating system, where the pipes may need to be flushed of debris build-up from time to time. 
   
4. No manifold needed - because it is electric, you will not need an underfloor heating manifold. A manifold system circulates water throughout the underfloor heating and transports water at the right temperature from either a heat pump or a boiler (through a blending valve). 
   
5. Localised heating - electric underfloor heating can be installed in one room instead of the whole house or workplace. You will not have to upgrade your central heating system. Because it will not need to be connected to a central manifold, an electric system can be installed in one room without compromising another. 

Disadvantages of electric underfloor heating

Electric underfloor heating is considered a safer option, but there are cons and potential dangers to be aware of.

1. Running costs - the running cost for electric underfloor heating can prove to be high in comparison to wet underfloor heating. The reason is that one unit of electricity costs more than a unit of natural gas which heats up the boiler that links to a wet underfloor heating system. As a result, electricity costs more to run - especially in larger rooms and spaces. 
   
2. Furniture placement - you have to be careful with where you place furniture after an electric system has been installed. For example, a piece of furniture with a flat bottom should not be placed over an area where cables or mats have been installed. This could cause damage to the flooring because the airflow is limited, resulting in hot spots. 
   
3. Difficult to fix - if any problems arise with the flow of heat, finding the issue with electric underfloor heating is tricky. Whereas with a water system, you are able to easily identify the problem area. 
   
4. Quick to lose heat - although electric underfloor heating is quick to heat up, it can also lose heat once quickly when turned off. It cools down much quicker than a wet underfloor heating system. 
   
5. Vinyl problems - the combination of vinyl flooring and electric underfloor heating is a potential issue. As a rule of thumb, it is advised that vinyl should not come into contact with temperatures above 27°C. Other flooring types should work well with an electric system. 

Electric vs water underfloor heating

Both electric and wet underfloor heating types have proved to be very effective, but they also come with possible problems. Before you go ahead with the installation, you should know the main differences and how you can benefit.

Can I use electric underfloor heating over timber flooring?

Electric underfloor heating for wooden floors will need to be supported with a base of plywood. This is to make sure that the heating system does not damage the timber. You will also be able to install electric underfloor heating underneath the concrete. To prepare, you will need to make sure the existing floor is stripped back, is free from any dust and is completely dry and flat. For the best results, add a layer of insulation - it will help to decrease downward heat loss. 

How to install electric underfloor heating

If you are not sure about where to start with installing electric underfloor heating, it is advisable to hire a professional with the correct skill and experience. Depending on the system you wish to lay, the floor height and the floor space size, the installation will be difficult and a professional is required to complete the job. But if you are confident about your DIY skills, you can install it yourself. Here are the steps you should follow to install electric underfloor heating.

1. Measure up

Before you start to install the system, be sure to measure the area where you want it to be placed. If installing it in a kitchen or bathroom, you should leave out installation under units. Another tip is to leave approximately 50mm of space around the edges of a room. 

2. Prepare your floor

You will likely find concrete substrate if you are installing electric underfloor heating downstairs. For upstairs - such as a bathroom - the substrate will likely be timber or plywood. An uncoated insulation board should be used for concrete and a coated insulation board for timber. Using an insulation board will allow a room to warm up quickly and help to reduce running costs. 

With a self-adhesive strip around the edge of a room, lay out the perimeter insulation foam and place the insulation boards on top of the floor. Create a brickwork effect as you move along. Make sure the floor is level and clean from any dust and dirt. You can use washers or screws to attach the boards to the substrate. 

3. Pinpoint unheated areas

For new builds, it is important to highlight any areas covered by fixtures such as sinks, toilets and bathtubs. To put this into context, if you place fixtures over any heating cables, it will limit the airflow to the floor. This will result in thermal blocking - the floor finish can become damaged and the heating system will overheat. 

4. Install the mat

To start the installation, it is best practice to begin where your thermostat will be (unless you have a smart thermostat). If you need to cut the mat at any awkward edges or corners, make sure to use scissors and be careful not to cut through any wires. Rotate the roll by 90 degrees with the wire side upwards and continue to lay the mat away from unheated areas. Keep repeating this method until you have covered the whole floor.

5. Secure loose wire

Space the heating wire at a minimum of 50mm when you come to secure the mesh mat from the loose heating wire section. To position this safely, it is important not to use fixing tape over the wire and not cross the wires. Using mesh tape will hold the heating wire in place and avoid issues such as wire failure and overheating. 

6. Add a floor sensor

This will help you to run your electric underfloor heating system more efficiently. In addition to the thermostat, an air sensor will help you to reduce your energy consumption. A floor sensor - controlled by a smart thermostat - works by identifying your room’s temperature via the heat that is coming from the floor. It can help to determine whether your underfloor heating system is overheated. Be sure that when adding a floor sensor, do not feed the heating wire into the wall. This could result in wire failure. 

7. Attach the mesh heating mat

After you remove the plastic backing, press down firmly onto the mat so it locks in its position and continue this until the whole area is covered. Make sure to not tape over the end electrical termination - this could cause overheating. But you can use fibreglass mesh tape which lets the levelling compound or tile adhesive through. Use fixing tapes for the mesh mat edges if they need to be fixed down more securely. 

8. Spare floor sensor and coil tail joints

It is recommended to cut in coil tail joints into the floor substrate or the insulation and fill the void with tile adhesive or self-levelling compound. Also, introduce a spare floor sensor - just in case the original floor sensor stops working. Simply place the sensor in between two heating wires - use fixing tape to secure everything in its place.

9. Lay the floor finish

For tiling over heating mats, you will first need to work tile adhesive through the mesh and over the cold tail joints. The heating wires should be completely covered by tile adhesive. Tiles should then be placed across the whole floor. When tiling over a self-levelling compound, make sure it covers all the heating wires and terminations. Before you tile the floor, spread tile adhesive across the full surface. 

10. Start using your electric underfloor heating 

You should hire a qualified electrician to make sure everything is connected correctly and safely. But before you turn the underfloor heating on, you need to wait between 7-14 days for the curing process to complete. After the process, turn on the thermostat and set the temperature to 27°C. The heating should be switched off and you should leave the floor limit at this temperature for 24 hours. 

How long does electric underfloor heating last?

On average, electric underfloor heating systems can last around 25 years. A couple of factors can affect the lifespan of electric underfloor heating.

1. General wear and tear

It is inevitable that a system will eventually lose its strength. Because an electric underfloor heating system turns on and off, this will affect its performance over time. 

2. Wrong materials

Poor quality wires used for the heating installation. The wires regulate how much voltage or current is sent through the system and the wire quality is important for the system to handle any heat fluctuations from the source of power. 

Electric or water underfloor heating vs radiators

If you are not sure whether to stay with traditional radiators or explore the option of electric or water underfloor heating, we have created a comparison table to help you make a decision.

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