Underfloor/Radiant Heating: A Step-by-Step Design Guide

Underfloor Heating Design Guide Introduction

When it comes to heating your home or building efficiently, underfloor heating—known as radiant heating in the USA—is a top contender.

With competitive price and timely delivery, Mufeng sincerely hope to be your supplier and partner.

This modern heating solution offers a range of benefits, from evenly distributing warmth across every room to reducing energy bills by operating at lower temperatures.

Whether you’re building new or retrofitting an existing space, a well-designed system can bring unparalleled comfort and energy savings.

In this guide, we’ll take you through the step-by-step process of designing an underfloor/radiant heating system.

Also, from calculating heat requirements and choosing the right pipe sizes to optimising flow rates and selecting the best manifold location, you’ll learn everything you need to know to ensure your system runs efficiently and effectively.

How To Design Underfloor/Radiant Heating

1. Manifold Placement and Setup

The heart of any underfloor (or radiant) heating system is the manifold.

Acting as the control centre, the manifold distributes heated water from the boiler or heat pump to the circuits under your floors.

Properly positioning and setting up the manifold is critical to ensuring the efficiency and performance of your system, whether you’re installing it in a small home or a large commercial space.

Suitable Placement for the Manifold:

• Centralised Location: Ideally placed centrally within the heated space to minimise the length of pipe runs and ensure even heat distribution.
• Accessible Area: Should be installed in a location that’s easily accessible for maintenance, such as a utility room, cupboard, or basement.
• Ventilated Space: Place the manifold in a well-ventilated area to prevent overheating and ensure the system operates efficiently.
• Avoid Damp Areas: Ensure the manifold is installed in a dry area, away from potential water damage.
• Height Considerations: For easier installation and maintenance, mount the manifold at a comfortable working height (typically between 1m to 1.5m from the ground).

Limitations to Consider:

• Distance from Heat Source: Avoid placing the manifold too far from the boiler or heat pump to minimise heat loss in the pipes.
• Pipe Length Restrictions: Limit the pipe runs from the manifold to prevent pressure drops and ensure consistent water flow; generally, pipe runs should not exceed 100m for a 16mm pipe.
• Space Constraints: The manifold requires sufficient space for installation, including enough clearance around the pipes, valves, and controls for easy access.
• Noise Sensitivity: In residential settings, avoid placing the manifold near bedrooms or living spaces, as it can produce operational noise.
• Multi-Story Buildings: In multi-story installations, consider separate manifolds for each floor to simplify the pipework and improve system control.

2. How to Calculate the kW/BTU for Underfloor/Radiant Heating

Before you can accurately size an underfloor (or radiant) heating system, it’s crucial to first understand the room’s heat loss.

The system’s heat output must match the heat loss to maintain a comfortable temperature.

Failing to account for the heat loss could result in a system that either underperforms, leaving rooms too cold, or wastes energy by oversizing the heating system.

Heat Loss:

Heat loss isn’t just about the size of the room; it also involves factors like insulation, window quality, and even heat lost through ventilation.

By calculating the total heat loss, you ensure that your underfloor heating system is appropriately sized to keep your space warm and efficient.

Additionally, factors contributing to heat loss include:

• Room Size and Surface Area: Larger rooms have more surface area for heat to escape, especially through walls, ceilings, and floors.
• Insulation Quality: Poorly insulated walls, floors, or windows increase heat loss significantly.
• Ventilation: Heat is also lost through ventilation, whether it’s natural airflow or mechanical systems like extractor fans.
• Desired Indoor Temperature: The greater the temperature difference between inside and outside, the higher the heat loss.

Heat Loss Formula:

Transmission losses

Each building component (walls, windows, roof, etc.) has its own U-value, measuring heat transfer, and requires separate calculations.

They are calculated using the following equation:

Metric:

Imperial:

Ventilation losses

This happens when hot indoor air is replaced by cooler outdoor air through ventilation or infiltration.

They can be calculated using the following equation:

Metric:

Imperial:

Where the Air Change Rate indicates how frequently the building’s air is completely replaced.

3. How to Calculate the Flow Rate for Underfloor/Radiant Heating

One of the key aspects of designing an efficient underfloor (radiant) heating system is calculating the correct flow rate.

The flow rate determines how much water needs to circulate through the pipes to deliver the required heat output.

Several factors determine this calculation, including the heat loss being overcome and the temperature difference between the supply and return water (ΔT).

What Is ΔT (Delta T)?

ΔT (Delta T) refers to the temperature difference between the water as it enters the underfloor heating system (flow temperature) and as it leaves (return temperature).

The value of ΔT influences the flow rate required to transfer the necessary heat to the room.

Typical values for ΔT:

UK Systems: Commonly designed with a ΔT of 5-10°C.

US Systems: Often use a ΔT of around 10-20°F.

Metric Flow Rate Formula:

The basic formula for calculating the flow rate is:

Flow Rate (L/s) = Heat Output (kW) / (ΔT × 4.18)

Where:

• Heat Output is the amount of heat required by the room, calculated in kW (kilowatts).
• ΔT is the temperature difference between the flow and return water (in °C).
• 4.18 is the specific heat capacity of water (in kJ/kg°C).

Imperial Flow Rate Formula:

Flow Rate (GPM) = Heat Output (BTU/h) / (ΔT × 500)

Where:

• Heat Output is the amount of heat required, calculated in BTU/h.
• ΔT is the temperature difference between the flow and return water (in °F).
• 500 is a constant based on the specific heat of water and conversion to GPM (gallons per minute).

How to Calculate Pipe Size for Underfloor/Radiant Heating

Selecting the correct pipe size is crucial to the efficiency and performance of your underfloor (or radiant) heating system.

The pipe size you choose affects the system’s overall energy consumption.

While the most commonly used pipe size is 16mm / 5/8″, variations in pipe diameter may be necessary depending on the specific requirements of the space you’re heating.

Simplify your heat load calculations in alignment with industry standards within h2x.

Common Pipe Sizes and Their Uses

• 12mm (3/8″) Pipes: Often used in retrofit projects with limited floor height. These pipes are smaller and easier to install in thin layers of screed but may require closer spacing and higher flow rates to achieve the same heat output.
• 16mm (5/8″) Pipes: The most common size for both residential and commercial underfloor heating installations. It offers a good balance between ease of installation, flow rates, and heat output. Suitable for most room sizes and floor types.
• 20mm (3/4″) Pipes: Typically used for larger or commercial spaces that require higher heat output over larger areas. These pipes allow more water flow, making them suitable for spaces with higher heat loss or larger floor areas.

Factors to Consider When Choosing Pipe Size

• Room Size and Heat Demand: Larger rooms with higher heat demands may benefit from larger pipes (e.g., 20mm or 3/4″) to ensure adequate heat output, while smaller rooms typically use 16mm or 12mm pipes.
• Pipe Length and Flow Rate: Longer pipe runs can create pressure drops and reduce system efficiency. The larger the pipe diameter, the lower the pressure drop, which can benefit large installations with long pipe runs. However, excessive pipe lengths should be avoided; pipe runs should typically not exceed 100m (328ft) for 16mm pipes.
• Pipe Spacing: Closer pipe spacing can compensate for smaller pipes, but wider pipe diameters typically allow for wider spacing without sacrificing heat output. For example:
• 100-150mm (4-6″) spacing is common for smaller pipes (12mm).
• 150-200mm (6-8″) spacing works well with standard 16mm pipes.
• 250mm (10″) or wider spacing may be used with larger pipes (20mm or more) in commercial applications.
• Floor Type: Certain floor finishes, like tiles or concrete, conduct heat more efficiently than wood or carpet, which may influence the pipe size and spacing needed. If a floor has poor thermal conductivity, you might opt for smaller pipes with closer spacing to ensure even heat distribution.
• Water Velocity: Keep the velocity of water within recommended limits—usually not exceeding 1 m/s (3 ft/s)—to avoid noise and excessive wear on the system.

How to Calculate Underfloor Heating Output

Determining the output of your underfloor (or radiant) heating system is essential to ensure that it can meet the heat demand of the room.

Several key factors, including pipe spacing, the type of floor finish, and the mean water temperature in the system, influence the heat output.

There are two primary methods to calculate the heat output of an underfloor heating system:

1. Manufacturer’s Data: Many manufacturers provide performance data for their specific underfloor heating products. This data often includes charts or tables that show heat output (in watts or BTU) for various pipe spacings, water temperatures, and floor finishes. Using this data allows you to design the system based on real-world testing of your components.
2. CIBSE (UK) or ASHRAE (US) Tables: For a more generalised approach, you can refer to industry-standard guidelines like the CIBSE tables (Chartered Institution of Building Services Engineers) in the UK or ASHRAE standards (American Society of Heating, Refrigerating and Air-Conditioning Engineers) in the USA. These tables offer guidance on typical heat output based on system design variables, such as pipe spacing and water temperature.

Key Factors Affecting Heat Output

• Pipe Spacing: The distance between the pipes in the system plays a significant role in the overall heat output. Closer pipe spacing increases the heat output, as more pipes distribute heat more evenly across the floor. Typical pipe spacings include:
• 100-150mm (4-6″): Provides higher heat output, ideal for spaces with higher heat demand or poor insulation.
• 200-300mm (8-12″): Suitable for well-insulated spaces with lower heat demand.
• Floor Finish: The type of floor covering dramatically affects the system’s ability to transfer heat. For example:
• Tiles and stone: Excellent heat conductors, allowing maximum heat transfer from the pipes to the room.
• Wood and laminate: Moderate conductors, often requiring slightly higher water temperatures or closer pipe spacing to achieve the desired heat output.
• Carpet: Acts as an insulator, reducing heat output. Systems designed for carpeted rooms may require smaller pipe spacing or higher water temperatures.
• Mean Water Temperature: The temperature of the water circulating through the pipes directly impacts the heat output. The higher the water temperature, the greater the heat output. However, the system should remain within recommended operational limits to avoid inefficiency or overheating. Typical flow temperatures range from:
• 35-55°C (95-131°F) for most residential systems.
• Higher temperatures may be necessary for poorly insulated spaces or those with less conductive flooring materials.

How to Work Out the Coil/Roll Length for Underfloor/Radiant Heating

Accurately calculating the coil or roll length required for your underfloor (or radiant) heating system is essential to ensure you have the right amount of pipe for your installation.

Factors like the total area being heated, the pipe spacing, and the system layout determine this calculation.

Having the correct coil length prevents delays, ensures optimal system performance, and avoids unnecessary wastage.

Key Factors to Consider

• Room Size: The total surface area of the heated space largely determines the overall pipe length.
• Pipe Spacing: The distance between the pipes significantly affects the required pipe length. Closer pipe spacing increases the total pipe length needed.
• Manifold Placement: The distance from the manifold to the heated area will also affect pipe length.
• Pipe Bends and Layout: Always account for extra pipe required for bends, connections, and any overlap between zones. It’s a good idea to add 5-10% to your calculated pipe length to cover these adjustments.
• Coil Sizes: Coils typically come in standardised lengths, such as 100m, 200m, or 500m. Be sure to choose the coil size that best fits your project to avoid wastage or having to join multiple coils.

Formula to Calculate Coil/Roll Length for Underfloor/Radiant Heating

Metric Formula:

Imperial Formula:

Where:

• Pipe Length: The total pipe length required for the room or zone.
• Pipe Spacing: The distance between each pipe loop (common values: 100mm – 300mm or 4” – 12”).
• Transit Pipe Length: The length of pipe required to connect the manifold to the heated area.
• 1.10: This multiplier adds 10% to account for extra pipe needed for bends and connections.

Underfloor/Radiant Heating Calculation Example

1. Heat Loss Calculation

First, calculate the room’s heat loss to determine how much heat is required.

And whilst this is a complex calculation, we will simplify it to keep this example concise.

Metric:

Imperial:

2. Flow Rate Calculation

At this point, once you know the heat loss / the desired heat output, you calculate the flow rate for the underfloor/radiant heating system.

Metric:

Flow Rate (L/s) = 2.4 kW / (10°C × 4.18) = 0.057 L/s

Imperial:

Flow Rate (GPM) = BTU/h / (18°F × 500) = 0.90 GPM

3. Pipe Size Calculation

For example, we will aim to use a 16mm (5/8″) pipe, which is commonly used in residential underfloor/radiant heating systems.

We need to verify the velocity is within the correct range, ideally less than 1m/s / 3 ft/s.

Metric:

Imperial:

You can also calculate fluid velocity flowing through pipes easily using our free online Pipe Velocity Calculator.

4. Heat Output Calculation

And then, the table below shows that a carpet floor finish, a room temperature of 20°C (68°F), and a mean water temperature of 40°C (104°F) require 200mm pipe spacing to achieve 60 watts per square metre.

CIBSE Underfloor Heating Design Guide ().

This also means the floor temperature is: 25.7°C (78.26°F).

5. Coil Length Calculation

Finally, calculate the coil length required for the underfloor/radiant heating system, including extra length for bends and connections.

Metric:

Imperial:

Summary:

Floor Finish: Carpet

Floor Temperature: 25.7°C (78.26°F)0.

Total Heat Loss: 2.4 kW ( BTU/h)

Flow Rate: 3.42 L/min (0.90 GPM)

Pipe Diameter: 16mm (5/8″)

Velocity: 0.50 m/s (1.64 ft/s)

Pipe Spacing: 200mm (8″)

Mean Water Temperature: 40°C (104°F)

Final Pipe Length: 225.5 metres (723.6 feet)

How h2x Can Enhance Your Underfloor Heating Design Guide

h2x software can simplify the entire process for your radiant aka underfloor heating design, from planning to implementation.

The tool automates calculations for pipe spacing, loop length, and heat output, ensuring accuracy and optimal performance.

Automatically generate loop layouts with required pipe spacings in h2x.

It also allows you to input specific project parameters, such as floor construction and desired temperatures, and instantly generates tailored layouts.

With detailed reports and CAD/Revit export options, h2x helps engineers present professional, client-ready designs for both new builds and retrofit projects.

Book a free demonstration or start a free trial with h2x today!

Underfloor Heating Design Guide FAQs

What is radiant/underfloor heating, and how does it work?

Radiant heating, also known as underfloor heating, is a system that heats a space by circulating warm water or using electric heating elements beneath the floor surface.

This provides even, comfortable heat throughout the room without the need for traditional radiators.

What’s more, our underfloor heating design guide above details insights into how these systems function.

Is radiant/underfloor heating more efficient than traditional radiators?

Yes, radiant/underfloor heating systems typically operate at lower temperatures, making them more energy-efficient compared to radiators.

They provide consistent heat, which can reduce energy consumption and lower utility bills, especially when designed according to industry best practices outlined in this underfloor heating design guide.

How much does it cost to install radiant/underfloor heating?

Installation costs vary depending on the size of the room and labour rates.

On average, radiant/underfloor heating systems in the UK range from £75 to £100 per square metre, while in the USA, they typically cost between $8 and $12 per square foot.

What is the running cost of radiant/underfloor heating?

Running costs depend on factors like insulation, room size, and energy prices.

Generally, radiant/underfloor heating is cheaper to run than traditional heating systems.

Furthermore, our underfloor heating design guide can help you predict running costs more accurately by tailoring the system to your needs.

If you want to learn more, please visit our website 3D Underfloor Heating Module.

In the UK, running costs can range from £4 to £6 per day, while in the USA, it may be around $5 to $8 per day.

Can radiant/underfloor heating be installed in existing homes?

Yes, radiant/underfloor heating can be retrofitted into existing homes.

However, they may require raising the floor height or additional structural work.

Nevertheless, using our underfloor heating design guide will help to avoid common mistakes and ensure the system delivers maximum comfort and efficiency.

What type of flooring works best with radiant/underfloor heating?

Tile, stone, and concrete are the most effective floor coverings for radiant/underfloor heating because they conduct heat well.

Wood and laminate can also work but may require careful temperature control, while carpet can insulate and reduce heating efficiency.

How long does it take for radiant/underfloor heating to warm up?

Warm-up times vary based on the system and floor type.

In fact, wet radiant/underfloor systems with tiles or stone may take 30-60 minutes.

However, these systems are designed to maintain a consistent, comfortable temperature rather than quick bursts of heat.

What’s the difference between wet and electric radiant/underfloor heating systems?

Wet radiant/underfloor heating uses warm water circulated through pipes beneath the floor, while electric systems use heated cables or mats.

Wet systems are typically more efficient for larger spaces, while electric systems are easier and cheaper to install in small areas or retrofits.

Is radiant/underfloor heating safe to use with all floor types?

Most floor types are compatible with radiant/underfloor heating, but following the manufacturer’s guidelines is important.

Also, some natural woods and high-resistance carpets may need special consideration or temperature regulation.

How do I control a radiant/underfloor heating system?

A thermostat typically controls radiant/underfloor heating systems, allowing you to set the desired temperature and schedule.

You can also integrate smart thermostats to control zones and optimise energy use.

Does radiant/underfloor heating increase home value?

Yes, radiant/underfloor heating is considered a premium feature that can increase the value of a property.

It’s particularly appealing in modern or energy-efficient homes and adds to overall comfort.

Can radiant/underfloor heating be used as the sole heating system in a home?

In well-insulated homes, radiant/underfloor heating can often serve as the primary heating system.

However, supplementary heating may be required in larger homes or spaces with high heat loss.

Moreover, our underfloor heating design guide above provides more detail about using UFH as a home’s sole heating system.

How long does radiant/underfloor heating last?

Radiant/underfloor heating systems can last 50 years or more when properly installed.

Can radiant/underfloor heating be repaired?

Yes, you can make repairs, but accessing the pipes or electric mats may require lifting floor sections.

It’s essential to hire a professional for repairs to avoid further damage to the system.

What are the benefits of radiant/underfloor heating?

Some of the benefits are: distributes heat evenly, improves energy efficiency, eliminates visible radiators, enhances indoor air quality (since no dust is circulated), and increases comfort.

Does radiant/underfloor heating work with renewable energy sources?

Yes, radiant/underfloor heating is highly compatible with renewable energy sources like heat pumps and solar thermal systems.

Furthermore, it works efficiently with the lower temperatures these systems generate.

While underfloor heating was once considered mainly an option for new builds or extensions, developments in product ranges and technology means it's now a viable option for heating your home even when renovating.

And, as well as being efficient and effective – offering a consistent heat throughout a room – it also offers aesthetic advantages such as freeing up wall space without the need for radiators.

However, with a variety of types available, how do you decide which is the best option for your particular project? Based on expert advice from Tim Pullen and those in the industry, we take a thorough look at underfloor heating so you can weigh up the pros, cons and understand which one best suits the needs of you and the construction of your home.

How does underfloor heating work?

Underfloor heating in either of its forms involves running a system of pipes or wires underneath the floor of a room. This effectively transforms the entire floor into one huge heat emitter that warms up the space.

Unlike radiators, which work by heating the air around them through convection, underfloor heating (UFH) uses both convection and radiant heat to warm a space. This combination of heating methods results in a consistent temperature which can be improved further by the addition of a good underfloor heating thermostat and and well-planned zones.

Heating from the ground up, also not only results in better comfort levels, but also puts less of a strain on your boiler when compared to traditional radiator systems. This is because of the lower operating temperature (around 40°C) of underfloor heating – radiator systems usually operate at around 65°C.

In fact, UFH is actually closer to being a ‘radiator’ than a radiator is. It heats the mass of the floor (the screed and the floor finish) and that heat then (mostly) radiates into the room – there is some convection going on but over 80% of heat transfer is by radiation.

It is also useful to note that underfloor heating is great when used in combination with renewable technology, such as heat pumps, which have a low flow rate.

Types of underfloor heating

There are two main types of underfloor heating:

• Wet underfloor heating
• Electric underfloor heating

In basic terms, a wet underfloor heating system features pipes, filled by warm water. Underfloor heating and boilers is one scenario, but underfloor heating with heat pumps is becoming an increasingly popular option. These pipes are typically embedded within a floor screed.

This is the best type of underfloor heating for those building from scratch and/or planning a whole-house system. However, there are also different types of wet underfloor heating depending on the type of floor you have and how it is constructed.

Wet underfloor heating: Your options

Wet underfloor heating comes in two different formats which means that asking how to install underfloor heating will give you two different answers, depending on whether you are building new, or relaying your floor from scratch.

• Buried underfloor heating: This system involves placing the pipes into the floor screed. The floor screed is finished, the pipes buried and the different zones are controlled by the underfloor heating manifold. This is the most efficient wet UFH system, but better suited to extensions and new builds where new floor screeds are required.
• Surface mounted underfloor heating: Also known as low profile systems, ths method involves specialist products that have warm water pipes installed in insulated panels. They are designed to be low profile, adding just 1.5cm to the floor level, making them more suitable for retro-fitting – as long as the increased floor level doesn't impact head space.

Electric underfloor heating: A good option for single rooms or retrofits

Wondering when you might need to consider electric underfloor heating instead? Simon Cook, head of sales at Nu-Heat explains that it generally comes down to the size and space you're looking to heat.

"Electric and wet underfloor heating systems are both great solutions when applied in the right scenarios," he says, "but while wet underfloor heating is an extremely efficient and effective whole house heating solution when paired with a bespoke design, it can require a larger upfront investment to install.

"Electric underfloor heating on the other hand is slightly cheaper to install, but far more costly to run. And, while it has a great response time, electric underfloor heating does lose heat a lot faster than warm water UFH. Therefore, it is best suited to small spaces such as kitchens or bathrooms."

Underfloor heating controls

The majority of underfloor heating system controls feature two main parts:

• A digital zone control that determines the temperature of each room/area
• The underfloor heating manifolds and valves that the zone control operates

The zone control will be placed somewhere where the homeowner can make adjustments, while the underfloor heating manifolds will be placed out of the way – under the stairs or in a cupboard – so as to be unobtrusive.

There is no regular maintenance regime associated with underfloor heating, although knowing how to bleed underfloor heating can help ensure it's working to the best efficiency. If things do go wrong, it will typically be with the heating control systems rather than the system itself. In both electric and wet systems, you'll need to consider the best underfloor heating thermostats to make sure you have the required amount of control over your heating.

It's also important to understand what temperature underfloor heating should be set at to ensure you are getting the best out of your system and managing your energy as wisely as possible.

Pros and cons of underfloor heating

What are the advantages of underfloor heating?

Although underfloor heating is a popular option when self building, it can be harder to decide when it comes to choosing it for a renovation project or extension in a house that already has a radiator led system.

However, the experts say it's a matter that needs serious consideration when you way up radiators vs UFH.

"While most homes in the UK are still reliant on traditional radiator systems, they aren't the best solution for everyone," says Simon Cook. "Of course, a key advantage to radiators is that they are already installed in most homes and so are familiar to most and can be simple to upgrade.

"But, before you decide to stick with radiators though, there are some major drawbacks to consider," he suggests.

"Radiators heat through convection, and as well as this leading to uncomfortable cold spots and draughts, the air circulation can also worsen conditions for allergy sufferers by spreading dust and allergens, all while taking up valuable wall space," says Simon.

"In contrast, although underfloor heating can involve a higher initial investment and may require a slight adjustment period, it offers numerous benefits for health, efficiency, and comfort," he notes.

"Underfloor heating warms the room evenly from the floor up through radiant heat, making it 25% more efficient than radiators and up to 40% more efficient when combined with a heat pump.

"And of course, UFH saves valuable wall space as it is neatly concealed beneath the floor," he adds, "eliminating the design restrictions created by radiators, giving you complete design freedom."

Of course, each decision to install UFH or radiators will be dictated property by property, room by room, depending on heat loss and whether the output from an underfloor heating system is larger than this loss figure.

It's also worth noting that underfloor heating systems have a lifespan of 50 years plus, while the average radiator will only last between 8-12 years before becoming inefficient.

A wet underfloor heating system is estimated to be 25% cheaper to run than radiators when attached to a modern boiler and 40% cheaper when attached to a heat pump. Electric underfloor heating is believed to be around three times more expensive than wet systems however, as electricity is more expensive.

What are the cons of underfloor heating?

Of course there are also downsides of UFH to consider – particularly if you plan to retrofit underfloor heating.

• Underfloor heating is more expensive to install than a comparable radiator system
• Installation time can be longer, especially with wet UFH. Even electric underfloor heating may require work to self level before installation
• When retrofitting underfloor heating, changes to floor height will need to be considered. This may require extra work in digging out the floor for a level profile
• Not all floor coverings will work as well with UFH

Underfloor heating and renovations

In a new build, the extra cost of underfloor heating relative to the whole build cost is seldom a deal breaker.

However, if you're looking to retrofit underfloor heating in a renovation project, it can be disruptive and expensive as it often involves taking up floors that may otherwise be best left alone, or raising the floor level, which may have implications on the joinery (doors, skirting etc).

Low-profile systems tend to have smaller diameter pipes and run at a higher temperature. This means that the floor will heat up and cool down far more quickly than conventional underfloor heating.

Where underfloor heating is added to an existing radiator system then a different control system will be needed. Luckily, wireless underfloor heating thermostats (some of which can be controlled with a app) make installation far easier.

It is often a good idea to install electric underfloor heating in a small, single area like a bathroom or en suite, where it may be difficult to install wet underfloor heating.

It is worth noting that one of the most common – and worst – uses for electric underfloor heating is in a conservatory. Typically these areas need a lot of heat and are used for relatively long periods of the day (compared to a bathroom, for example). This means that running costs become an issue and the extra trouble and expense of a wet system may be well worthwhile.

Choosing the best flooring to use with underfloor heating

When it comes to choosing the best flooring for underfloor heating, there are a number of options available – some more suitable than others.

Although underfloor heating with tiles is one of the most popular combinations, there are pros and cons and specific requirements for other options such as UFH with laminate flooring and wooden flooring with underfloor heating.

Likewise, while underfloor heating with carpet can be considered, it won't be as efficient as when used with harder materials such as ceramic and porcelain tiles, luxury vinyl tiles and natural stone flooring.

Concrete is a superb heat conductor, so polished concrete floors also work really well with underfloor heating as the thermal mass of your concrete will retain heat and ensure your room stays warm for longer after your heating is switched off than would be the case with a radiator system. They are easy to pour over the pipework and they absorb and hold the heat produced well. Seek the advice of your installer before switching your underfloor heating on though – too soon and it could crack.

Most retailers will specify whether a flooring will work with underfloor heating, so look for that as your first guide when choosing what you will use to cover the floor.

FAQs

Should I leave underfloor heating on all the time?

Understanding how long does it take underfloor heating to warm up will help guide you towards the best way to run your heating.

With a wet system it can take two or three hours to warm up, so it is better to leave it turned on if you or your family are inside the house and need to keep warm.

To save costs, you can adjust the temperature instead, to make it lower during night time or times when you might not be using the space.

With electric underfloor heating meanwhile, the floor can heat up much quicker. The heating costs depend on how many kilowatts hours (kWh) of electricity you use and this will be more, the longer the heating is turned on or the more watts the underfloor heating uses. For a 125W system turned on for an hour, for example, this will use 1KWh for every eight square metres of electric underfloor heating

How thick should underfloor heating screed be?

The thickness of the floor screed during your installation process will make all the difference. The screed thickness in which the warm wet pipes sit will have a dramatic impact on how the system is used.

A thick screed will give a longer reaction time (the time taken to warm up and cool down), while a thin screed will have a quicker reaction time.

Which is right and best will depend on the construction of the house, your occupation habits and how the underfloor heating system is to be used, however, the following offers some guidance:

• If the pipes are housed in the concrete floor slab, this should be 150mm thick and give a reaction time of over four hours. In this situation, it is best to run the system all day, at a lower room temperature – say 15°C or 16°C – to provide background heating to the whole house. Highlight heating, such as a log burning stove, is a good idea in the rooms that are occupied
• A standard sand and cement screed would typically be 65mm to 75mm thick and the underfloor heating could take upwards of two hours to heat the room or cool down. This situation may be well-suited to rooms where we spend a lot of time, such as lounge or kitchen, but might be less acceptable in a guest bedroom
• With thinner flow screeds, we might expect a thickness of 35mm to 40mm and a reaction time of around 30 to 40 minutes – the system can be run in a similar way to a radiator system. Flow screeds offer better thermal conductivity than sand and cement, and being thinner and lighter means that they can be suitable for both renovations and new builds

How much does underfloor heating raise floor levels?

Underfloor heating will usually raise the profile of the floor. The amount it is raised by will depend on a number of factors such as how much insulation you need to add, pipe size, and whether you need a screed and floor finish.

There are also some products that get ‘carved’ into an existing screed, in which case there would be no additional build up other than the final floor finish.

If you want to retrofit a wet water system or have concerns about excavating or raising the floor, then low profile systems are a good option. "These have the advantage of coming in different heights and designs which allows them to be installed relatively quickly and easily on most substrates without impacting on the floor to ceiling height of the room," says Mark Dowdeswell, Senior Category Manager at Uponor.

Where should I buy underfloor heating?

Ultimately, the efficiency and success of an underfloor heating system will depend on the quality and design. Choosing a supplier who offers a good design service and aftercare is important. A specialist underfloor heating company is often best placed to achieve this.

If the design is wrong it is unlikely that the homeowner will know until they have lived in the house for a whole heating season – by which time it might be too late.

Finally, if you are choosing to pair underfloor heating with an air source heat pump or ground source heat pump, it is a good idea to choose one supply and install company. Both are complex systems and getting the whole heating system to work in perfect harmony is essential to a warm and toasty home.

For more information, please visit Underfloor Heating Staple Gun.