When designing an underfloor heating (UFH) system, one of the most common questions is:

Should I use 12mm or 16mm MLCP pipe?

Both pipe sizes are widely used in modern underfloor heating systems, but they perform very differently in terms of:

• Heat output
• Flow rate
• Pressure loss
• Maximum loop length
• Installation flexibility

In this guide, we’ll compare 12mm vs 16mm MLCP pipe and explain which is best for different UFH applications.

What Is MLCP Pipe?

MLCP stands for Multi-Layer Composite Pipe.

It combines:

• An inner PE-RT or PEX layer
• An aluminium core
• An outer protective plastic layer

This construction gives the pipe:

• Excellent flexibility
• Shape retention
• Low thermal expansion
• Oxygen barrier protection
• High durability for heating systems

MLCP is now one of the most popular choices for wet underfloor heating systems in the UK.

Heat Output Comparison: 12mm vs 16mm MLCP Pipe

The biggest difference between the two pipe sizes is the amount of heat they can transfer into the floor.

Because 16mm pipe has a larger surface area and carries more water, it can generally emit more heat per metre than 12mm pipe.

Typical Heat Output at 50°C Flow Temperature

Actual output depends on floor finish, screed depth, pipe spacing and room temperature.

In most UFH systems, 16mm MLCP pipe delivers approximately 30–35% more heat output per metre compared to 12mm pipe.

Why Does 16mm Pipe Produce More Heat?

The main reason is simple:

Larger Pipe = More Surface Area

16mm pipe has:

• Greater external surface area
• Higher water volume
• Increased flow capacity

This allows more thermal energy to transfer into the floor structure.

Surface Area Comparison

That additional surface area directly improves heat transfer performance.

Flow Rates & Hydraulic Performance

Heat output is only part of the equation.

Pipe size also dramatically affects:

• Water flow rates
• Pump pressure
• System balancing
• Loop lengths

12mm MLCP Pipe

Advantages

• Easier to bend
• Ideal for low-profile retrofit systems
• Better for tight installation areas
• Faster floor response times in some overlay systems

Disadvantages

• Higher resistance to flow
• Shorter loop lengths required
• Higher pressure drops
• Lower overall flow capacity

Typical maximum loop length:

• Around 50–70 metres

16mm MLCP Pipe

Advantages

• Lower pressure loss
• Longer circuit lengths
• Better overall efficiency
• Higher heat output potential
• Easier manifold balancing

Disadvantages

• Larger bending radius
• Requires deeper floor build-up
• Slightly slower response in thick screeds

Typical maximum loop length:

• Around 80–120 metres

Which Pipe Size Is Best for Underfloor Heating?

Choose 12mm MLCP Pipe If:

You are installing:

• Low-profile retrofit UFH
• Overlay panel systems
• Renovation projects with limited floor height
• Small rooms or short heating circuits

12mm pipe is extremely popular in:

• Timber floor retrofits
• Upstairs renovations
• Existing property upgrades

Choose 16mm MLCP Pipe If:

You are installing:

• New build UFH systems
• Screeded floors
• Large open-plan areas
• High heat demand rooms

16mm remains the industry standard for most wet underfloor heating systems because it offers:

• Better hydraulic performance
• Easier system balancing
• Greater heat transfer
• Longer circuit capability

Does Smaller Pipe Heat Up Faster?

Technically, yes.

Because 12mm pipe contains less water volume, it can respond slightly faster to temperature changes.

However, in real-world UFH systems, floor construction and screed thickness usually have a much bigger effect on response time than pipe diameter alone.

Final Verdict: 12mm vs 16mm MLCP Pipe

There is no universal “best” option — it depends entirely on the application.

In Summary

Overall Recommendation

• 12mm MLCP is ideal for retrofit and low-profile UFH systems.
• 16mm MLCP is generally the better choice for maximum heat output and system efficiency.

For most new-build underfloor heating installations, 16mm MLCP remains the preferred option.

Need Help Designing Your UFH System?

Choosing the right pipe size is critical for:

• Correct heat output
• Efficient flow rates
• Proper loop balancing
• Long-term system performance

Whether you’re designing a retrofit overlay system or a full screeded UFH installation, selecting the correct MLCP pipe diameter can make a huge difference to overall efficiency and comfort.

The post 12mm vs 16mm MLCP Pipe for Underfloor Heating appeared first on The Underfloor Heating Site.

Why installers usually go with one manifold per floor

1. Better temperature control (zoning)

Each floor has different heating needs:

• Ground floors lose heat to the ground
• Upper floors retain more heat
• Lofts and basements behave very differently

A manifold per floor lets you:

• Control each floor independently
• Set different temperatures and schedules
• Avoid overheating upstairs while trying to warm downstairs

2. Easier system balancing

Underfloor heating relies on balanced flow through each loop. With a manifold per floor:

• Pipe runs are shorter and more consistent
• Flow rates are easier to adjust
• Less risk of some rooms not heating properly

3. Shorter pipe runs = better efficiency

If you try to serve multiple floors from one manifold:

• Some loops become very long
• You may need a larger pump
• Heat losses increase in the distribution pipework

Keeping manifolds local to each floor keeps things efficient.

4. Simpler installation and maintenance

• Easier to install in stages (floor by floor)
• Faults can be isolated to one floor
• More accessible if placed in cupboards on each level

When a single manifold might be acceptable

You might get away with one manifold if:

• The property is small (e.g. compact 2-storey)
• Total floor area is relatively low
• Pipe runs can all be kept within recommended lengths (~80–100m per loop)
• Heat loads across floors are similar

Even then, many installers still prefer splitting by floor.

Typical “good practice” layout

• One manifold per floor
• Located centrally on that floor (cupboard, utility space, etc.)
• Each room has its own loop (or multiple loops for larger rooms)
• Controlled via individual room thermostats and actuators

Rule of thumb

Go with a manifold per floor if:

• You have 2+ storeys
• Total area is over ~100 m²
• Different floors are used differently (e.g. bedrooms vs living areas)
• You want proper zoning and energy efficiency

Bottom line

It’s not a strict requirement, but a manifold per floor is the preferred approach because it gives you:

• better control
• better efficiency
• easier installation and commissioning
• fewer headaches long term

The post Is it best practice to have a manifold per floor for water-based UFH? appeared first on The Underfloor Heating Site.

Step-by-step: Laying loose UFH cable

1. Prepare the subfloor

• Surface must be clean, dry, and level
• Install insulation boards (very important for efficiency)
• Prime the surface if required (especially for screed/adhesive)

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2. Plan your layout carefully

• Avoid fixed objects: toilets, cabinets, kitchen units
• Maintain consistent spacing (usually 50–100mm between runs)
• Never cross cables
• Mark out your layout before you start

Tip: Keep cables slightly closer together in colder zones (like near external walls)

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3. Fix the cable in place

You have 3 main fixing methods:

• Fixing strips (best option) – pre-spaced clips for even layout
• Hot glue / tape – for small areas
• Mesh systems – if partially pre-mounted

Lay in a zig-zag pattern for even coverage.

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4. Install the floor sensor

• Place it centrally between two cable runs
• Run inside a conduit (so it can be replaced later)
• Avoid touching the heating cable directly

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5. Test before covering

• Use a multimeter to check resistance
• Compare with manufacturer specs
• Test again after installation

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6. Cover the cable

7 Options:

• Self-levelling compound (SLC) → best for most installs
• Tile adhesive (for tiles only)
• Screed (for thicker builds)

Make sure cables are fully embedded and protected.

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Common mistakes to avoid

• Crossing or touching cables (causes overheating)
• Uneven spacing → hot/cold spots
• No insulation → massive heat loss
• Cutting the heating cable (only trim the cold tail)
• Skipping testing

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Pro tips

• Take photos before covering (helps if you drill later)
• Use a thermostat with floor probe for better control
• Plan cable spacing based on required wattage (not guesswork)

Is a decoupling mat a good idea when using loose cable?

Short answer: yes—using a decoupling mat with loose cable UFH is often a very good idea, especially under tiles. But it depends on your floor build-up and goals.

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What a decoupling mat does

A decoupling mat (like Schluter-DITRA-HEAT or similar systems) acts as:

• Movement buffer → prevents tile cracking from subfloor movement
• Cable holder → keeps spacing perfectly consistent
• Stress relief layer → ideal over timber floors or mixed substrates

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When it’s a great idea

Use a decoupling mat if:

• You’re tiling over timber floors (plywood/OSB)
• The subfloor has potential movement or slight flex
• You want easy cable layout with no guesswork spacing
• You want a premium, belt-and-braces install

In these cases, it’s often better than fixing strips.

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When it’s not essential

You don’t strictly need it if:

• You have a solid concrete/screed subfloor
• The floor is already very stable
• You’re happy using fixing strips + self-leveller

In those cases, a decoupling mat is more of a nice upgrade than a necessity.

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Downsides to consider

• Cost – mats aren’t cheap
• Floor height – adds a few mm build-up
• Slight thermal lag – tiny delay vs direct embed (usually negligible)

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Best practice if you use one

• Fully bond the mat to the subfloor (no voids)
• Press the cable firmly into the channels (don’t force it)
• Still install a floor probe sensor between runs
• Tile directly on top using flexible adhesive

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Honest verdict

• Timber floor + tiles → absolutely worth it
• Concrete floor → optional upgrade
• DIY install → makes life MUCH easier

The post How to Install Loose Cable Underfloor Heating (The Right Way) appeared first on The Underfloor Heating Site.

Both PERT-AL-PERT and PEX-AL-PEX pipes are multilayer composite pipes made of:

• Inner plastic layer
• Middle aluminium layer (for strength + oxygen barrier)
• Outer plastic layer

They’re widely used in plumbing and heating systems.

PEX-AL-PEX Pipe

4

Inner layer: Cross-linked polyethylene (PEX)

Key characteristics:

• Very strong and rigid
• Excellent temperature and pressure resistance
• “Shape memory” — holds its form once bent
• Slightly harder to bend than PERT

Best for:

• High-pressure plumbing systems
• Radiators and heating systems
• Long-term durability installations

PERT-AL-PERT Pipe

Inner layer: Polyethylene of Raised Temperature Resistance (PERT)

Key characteristics:

• More flexible and easier to install
• Can be bent tighter without tools
• Slightly less rigid than PEX
• Good temperature resistance (but not quite as tough as PEX long-term)

Best for:

• Underfloor heating (very popular choice)
• Systems where flexibility reduces install time
• Retrofits or tight spaces

Key Differences (Simple Comparison)

Can they be used for potable (drinking) water?

Yes — both can be used for potable water, provided they are certified (e.g. WRAS approval in the UK).

They are:

• Non-corrosive
• Smooth inside (resist scale buildup)
• Safe when properly rated

Can they be used for underfloor heating?

Yes — both are suitable, but:

• PERT-AL-PERT is often preferred
  → easier to lay in loops
  → quicker installation
• PEX-AL-PEX is also excellent
  → slightly tougher
  → holds shape better when clipped

Bottom line

• Choose PEX-AL-PEX if you want maximum durability and rigidity
• Choose PERT-AL-PERT if you want easier installation and flexibility (especially for underfloor heating)

The post What are the key differences between Pert-al-Pert Pipe and Pex-al-Pex pipe? appeared first on The Underfloor Heating Site.

Screed UFH vs Overlay UFH (simple view)

Screed UFH (traditional “in-slab”)

6

What it is:
Pipes are embedded in a thick layer of screed (cement or liquid anhydrite).

Pros

• Stable, even heat thanks to thermal mass
• Holds heat for hours after switching off
• Works at lower water temperatures (30–40°C) → ideal for heat pumps
• Generally most efficient long-term

Cons

• Slow to respond (takes hours to heat up)
• Needs drying/curing time before flooring
• Raises floor height significantly
• More disruptive install

Think of it like a storage heater: slow but very steady.

Overlay (low-profile) UFH

8

What it is:
Pre-formed boards (often EPS or chipboard) sit on top of your existing floor, with pipes in grooves.

Pros

• Fast response – heats up quickly
• Minimal floor build-up (great for retrofits)
• Quick install (no long drying times)
• Can often be used room-by-room

Cons

• Doesn’t store heat (cools quickly)
• Often needs higher water temps (45–55°C)
• Slightly less efficient with heat pumps
• Can feel more like radiators (on/off cycling)

Think of it like a radiator in the floor: quick but not “soak heat”.

The real-world difference

1. Heat behaviour (most important)

• Screed = slow, constant, background heat
• Overlay = quick, responsive, on-demand heat

This is the biggest deciding factor.

2. How you live matters

• If you want heating on all day at a steady temp → screed wins
• If you want to turn rooms on/off quickly → overlay wins

3. Build context

• New build / extension: almost always screed
• Renovation / upstairs / low ceiling: overlay

4. Running costs

• Screed can be cheaper long-term, especially with heat pumps
• Overlay may cost slightly more to run due to higher temps

Quick recommendation

• Go screed UFH if:
  • You’re building from scratch or doing major renovation
  • You’re using a heat pump
  • You want maximum efficiency + comfort
• Go overlay UFH if:
  • You’re retrofitting into an existing house
  • Floor height is tight
  • You want faster responsiveness

Bottom line

There isn’t a “better” system universally:

• Screed = comfort + efficiency (but slow + disruptive)
• Overlay = convenience + speed (but less thermal performance)

The post Which water UFH system should I go for – In-screed or overlay appeared first on The Underfloor Heating Site.

Air source heat pumps (ASHPs) are becoming a go-to solution for low-carbon heating, especially when paired with underfloor heating (UFH). If you’re planning a setup with 16mm underfloor pipes and a fl

ow temperature of 45°C, you might be wondering: how much 

heat output per square meter can I actually expect?

Let’s break it down in simple terms.

What Determines Heat Output?

When using underfloor heating with an ASHP, the heat output (measured in watts per square meter, or W/m²) depends on a few key factors:

1. Flow and return temperatures – These affect the average water temperature.

2. Pipe spacing – The closer the pipes, the more even and higher the heat output.

   

3. Floor construction – Screed depth, insulation, and surface materials (like tile, wood, or carpet) all impact performance.

4. Room temperature – The bigger the difference between the floor and the room, the more heat is transferred.

A Typical Setup: The Numbers

Let’s assume a fairly standard UFH installation with the following specs:

• Pipe size: 16mm (common for UFH)

• Flow temperature: 45°C

• Return temperature: 35°C (typical for ASHP setups)

  

• Pipe spacing: 150mm

• Floor surface temperature: Around 27–29°C

• Room temperature: 20°C

This gives us an average water temperature of 40°C, and a temperature difference (ΔT) betwee

n the floor and the room of roughly 7–8°C.

Estimated heat output: 70–90 W/m²

This is usually sufficient for well-insulated homes built to modern standards, especially in living spaces and bedrooms.

A Few Quick Examples

The lower the flow temperature, the less heat you’ll get—but the more efficient your heat pump becomes. It’s all about finding the sweet spot between comfort and efficiency.

Pro Tips for Better Efficiency

• Insulate properly – Floors, walls, and especially under the screed.

• Use tight pipe spacing in high-demand areas (like 100mm in bathrooms).

• Choose the right floor finish – Tiles and stone transfer heat better than carpet or thick wood.

• Zone your system – Independent control for rooms improves comfort and efficiency.

So, Is 45°C Good for Underfloor Heating?

Yes! A 45°C flow temperature is ideal for combining an ASHP with underfloor heating. It provides good heat output without overworking the heat pump, maintaining excellent system efficiency.

If your home is well insulated, you might even get away with lower temperatures, which means even more savings and a greener footprint.

Wrapping Up

Underfloor heating paired with an air source heat pump offers a low-energy, comfortable heating solution. With a 16mm pipe and 45°C flow temp, expect around 70–90 W/m², enough to keep your space cozy while keeping running costs down.

Want to get the best out of your setup? Focus on insulation, pipe layout, and smart temperature control—and your ASHP + UFH system will serve you well for years to come.

The post 🏡 Using an Air Source Heat Pump with Underfloor Heating: How Much Heat Output Can You Expect? appeared first on The Underfloor Heating Site.

In short it’s a resounding YES from us but don’t juts take our word for it the results speak for themselves.

See below for some output information for the routed chipboard system with 6mm plywood cover boards.

• All simulations were done using 12mm pipes
• The numbers in the table is the average temperature on the top surface.

Since those case are isothermal, water temperature is constant 35 degrees and 55 degrees respectively.

The post Is Foiled Chipboard For Underfloor Heating Worth it? appeared first on The Underfloor Heating Site.

Are you looking to heat your home but unsure whether to choose underfloor heating or radiators? It can be a difficult decision to make – with so many factors to consider, such as cost, efficiency, installation, and maintenance. But the answer might surprise you! In this blog post, we’ll explore the cost comparison between underfloor heating and radiators, so you can make an informed decision on the best heating solution for your home.

Introducing the two types of heating

When it comes to heating your home, there are two main options you can choose from – radiators or underfloor heating. Radiators are typically used in many homes and have been around for a long time. They use hot water heated by a boiler to provide heat. Underfloor heating on the other hand, is a more modern method that uses electric heating mats laid underneath your flooring. This type of heating tends to be more efficient than traditional radiators because it warms up the entire room instead of just one specific area. It also offers more flexibility in terms of design and can be used in almost any room. Both radiators and underfloor heating have their pros and cons, so let’s take a look at which one is cheaper.

The initial cost

When it comes to the initial cost of installing underfloor heating or radiators, there is no one answer that fits all. The type of heating system you choose will depend on your individual needs and budget.
Underfloor heating is typically more expensive than radiators when it comes to installation. This is because the installation process requires the laying of either electric cables or pipes into the flooring, which takes a significant amount of time and effort. However, this cost may be offset by the fact that it requires fewer radiators, so there are often fewer materials needed for the installation.
Radiators are generally cheaper to install as they don’t require any additional flooring or pipework to be fitted. Additionally, since radiators don’t require any additional building work, they can often be installed in a relatively short amount of time.
Ultimately, the cost of installation will depend on the type of heating system chosen, the size of the area, and the complexity of the job. It’s best to speak to a qualified installer to get an accurate quote before making a decision.

The running cost

When considering the long-term costs associated with heating your home, the running cost is a key factor to consider. Both underfloor heating and radiators are typically powered by electricity or gas, so both can have relatively high running costs depending on the fuel source.
Underfloor heating tends to be more efficient than radiators because it requires less energy to heat up a room. It also takes longer to heat a room as the heat is distributed evenly and slowly, but this means that once it has been turned on it takes less energy to maintain the desired temperature, resulting in lower running costs.
Radiators, however, tend to be more expensive to run because they have to be turned on and off frequently in order to maintain a constant temperature. Radiators also take more energy to heat up a room as the heat is distributed quickly and unevenly.
Overall, underfloor heating usually provides greater cost savings over the long-term than radiators. This is due to its more efficient use of energy, which leads to lower running costs.

Maintenance costs

When it comes to the cost of maintenance, there is not much difference between underfloor heating and radiators. Both systems require a yearly check-up and general upkeep to keep them functioning optimally. Depending on the type of underfloor heating you choose, however, you may require additional maintenance for your underfloor system such as repairs to the pipes or the water pump.
The biggest difference between the two types of heating systems when it comes to maintenance costs is the fact that radiators need to be regularly replaced due to wear and tear. Underfloor heating systems are typically much more durable and often last a lifetime without needing any replacement parts.
Overall, both underfloor heating and radiators have their own pros and cons when it comes to maintenance costs. To help determine which one is right for you, it’s important to weigh up all the factors involved including initial cost, running cost and long-term maintenance costs.

Which one is cheaper in the long run?

When it comes to the long-term costs of heating your home, both underfloor heating and radiators have their own pros and cons. The initial cost of installing underfloor heating can be more expensive than radiators, depending on the type you choose. However, running costs can be much lower with underfloor heating as it distributes heat more evenly throughout the home and can be controlled easily to avoid over-heating or wasting energy.
On the other hand, while radiators are less expensive to install initially, they may not be as cost-effective when it comes to running costs. Radiators need to be individually adjusted and can be prone to hot spots, leading to wasted energy and higher bills.
In terms of maintenance, radiators require more frequent cleaning and servicing, which can add up over time. Underfloor heating is low maintenance and typically requires only an annual check-up.
So when it comes to which is cheaper in the long run, it really depends on your individual circumstances. If you’re looking for a low-maintenance system with reduced energy costs, then underfloor heating could be the more cost-effective option for you. But if you’re looking for a cheaper installation cost and don’t mind doing a bit of extra maintenance, then radiators may be the best choice.

The post Is Underfloor Heating Cheaper Than Radiators? The Answer Might Surprise You! appeared first on The Underfloor Heating Site.

Are you considering installing underfloor heating in your home? If so, you may have questions about the cost of running it. In this blog post, we’ll take a look at the answer to the question “Is underfloor heating expensive to run?” We’ll look at factors such as energy efficiency and maintenance costs, to help you make an informed decision. So read on to find out more!

The upfront cost

When considering underfloor heating, the upfront cost can be a major factor. The cost of installing an underfloor heating system varies depending on the size and complexity of your property and the type of system you choose to install. Generally speaking, wet systems are more expensive than electric systems and will also require a professional installer.
If you’re looking to install an electric system, then the costs can vary from a few hundred pounds for a small area to several thousand for larger spaces. This cost will include all materials, plus any labour fees for installation and commissioning. When calculating costs, it’s important to remember that the total cost of installation can include any modifications that need to be made to your existing home in order to accommodate the new system.
For wet systems, you can expect to pay between £4,000 and £6,000 for a typical three-bed semi-detached house. This cost is likely to increase if you have a bigger space or if there is additional work required. As well as installation costs, there may be additional costs associated with things like plumbing or drainage works. It is therefore important to get a detailed quotation from your installer before you commit to any installation.

The running costs

When it comes to running costs, underfloor heating can be a great option, as it is more energy efficient than traditional radiators. According to the Energy Saving Trust, running an electric underfloor heating system costs around 10p per hour to run. This compares favourably with other types of heating systems, such as gas central heating which can cost around 25p per hour.
The cost of running your underfloor heating will vary depending on a number of factors, including the type and size of the system, the insulation of your home, the power output of the system, and the amount of time it is switched on. To get an accurate idea of your running costs, it’s best to get a quote from a qualified professional.
The running costs of an underfloor heating system are affected by the same factors as any other heating system, such as the age and condition of the system and your own energy-saving practices. To save money, you should always make sure your underfloor heating is switched off when not in use and keep your thermostat settings low during the winter months. It’s also a good idea to invest in good quality insulation for your home. This will help to keep your home warm and reduce your heating costs.

The benefits

Underfloor heating is an excellent addition to any home, offering a wealth of benefits. Firstly, it provides excellent comfort as the heat rises evenly throughout the space. This means that no areas will be left cold, as can often be the case with radiators.
The heating is also gentle and quiet, so it won’t interfere with your day-to-day activities. The system also allows you to have complete control over your thermostat settings, allowing you to adjust the temperature as needed.
Finally, underfloor heating is an energy efficient form of heating. As it works from the ground up, it requires less energy than other forms of heating. This means lower running costs for you, saving you money in the long run.

The drawbacks

When it comes to underfloor heating, one of the main drawbacks is the upfront cost. Installing a system can be quite expensive, and even more so if you’re installing it on an entire floor. In some cases, you may need to make structural modifications to your home in order to accommodate the system.
Another potential issue with underfloor heating is that it can take a while to heat up and can cool down quickly as well. This means that it may not be suitable for those who require a quick warm up or need to maintain a consistent temperature throughout their home.
Finally, underfloor heating can also be difficult to install, particularly if you have an irregularly shaped room. It requires precise measurements and the right materials in order to ensure proper functionality. Hiring a professional is often recommended, which can add to the overall cost.

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