Water Underfloor Heating – Frequently Asked Questions

How does the manifold work in a water underfloor heating system?

The manifold is the system’s central control unit, distributing hot water evenly through each heating loop under the floor. It consists of two rails: the flow manifold supplies warm water while the return manifold collects cooler water to be reheated. Flow meters and balancing valves regulate how much hot water goes to each zone, ensuring even temperature distribution.
Actuators connected to the manifold open or close the valves based on thermostat signals, allowing precise control of each room or zone. This balancing prevents cold spots and optimizes energy use effectively.

How does the wiring centre work with actuators and why is it needed for zone control?

The wiring centre acts as the centralized electrical hub connecting thermostats, manifold actuators, pump, and boiler controls. When a thermostat calls for heat, the wiring centre signals the corresponding actuator to open its valve, allowing water into that zone.
This enables independent temperature control across multiple zones (rooms), improving comfort and reducing waste by heating only occupied spaces.

Why is zone control important to save money and regulate temperatures?

Zone control enables heating different areas independently, with thermostats and actuators adjusting heating circuits per room or zone.
This results in personalised comfort by allowing different temperatures where needed and savings because unused zones can remain unheated. Zone control optimizes energy consumption, reduces overall heating costs, and maximizes system efficiency, especially beneficial in multi-room homes, HMOs, or buildings with variable occupancy.

Is water underfloor heating compatible with heat pumps?

Yes, water underfloor heating works exceptionally well with heat pumps as both operate efficiently at the lower water temperatures (typically 35–50°C) that underfloor systems require.
We offer a combined solution for around 15 sqm areas: the 15.0m 4kW Monobloc Heatpump and Multi-Zone Water Underfloor Heating Combined Pack, ideal for cost-effective, efficient heating.
This synergy lowers running costs and boosts renewable heat use.

Why is water underfloor heating more efficient in larger spaces?

Water underfloor heating is generally more cost-effective and efficient for heating larger areas (typically greater than 50 sqm) because it can circulate heat at lower energy than electric systems, using pumped hot water instead of electricity.
The system provides an even heat distribution at low temperature, ideal for whole-house or multiple-room installations. For smaller areas or retrofits, electric underfloor heating systems may be more practical.

What is a single room underfloor heating kit?

A single room underfloor heating kit includes all the essential components required to install underfloor heating in one room. This typically comprises pipes, manifolds, controls, and fittings, designed to work seamlessly together, simplifying installation and ensuring full compatibility.

Importantly, these kits can often be connected to your existing radiator heating circuit, allowing you to integrate underfloor heating into your current central heating system without needing a complete overhaul. This makes them an ideal solution for retrofitting or upgrading individual rooms to enjoy the comfort and efficiency of underfloor heating while utilizing your existing boiler and pipework.

Explore our range of single room kits here: Single Room Underfloor Heating Kits.

What is Thermrite Protile XPS insulation and why is it beneficial?

The Thermrite Protile 20mm XPS Insulation Panel combines extruded polystyrene’s (XPS) excellent resistance to moisture and compression with a surface suitable for tiling directly on top. XPS provides superior thermal insulation and durability compared to expanded polystyrene (EPS), preventing heat loss into the subfloor and improving overall underfloor heating efficiency.

What options exist for joisted floors and lightweight flooring applications?

Timber and joisted floors require specially designed UFH systems that avoid damaging the structure or floor covering. Our Joisted Floors Underfloor Heating Collection offers suitable solutions.
For lightweight screed alternatives and floor levelling, explore our Profix Underfloor Heating Range, designed for faster installation and minimal floor height.

Why use multiple manifolds on different floors?

Using multiple manifolds for different floors or zones helps optimize supply and return management according to varying heating demands per floor. This improves hydraulic balancing, simplifies maintenance, and allows tailoring flow rates per zone for better comfort and efficiency.
It also reduces pump workload and helps avoid pressure imbalances that can impact performance and cause noise.

Why is a mixing unit with a pump important?

A mixing unit blends hot water from the boiler or heat pump with cooler return water to deliver the optimal flow temperature (usually 35-50°C) necessary for underfloor heating, preventing damage and improving comfort.
The integrated pump circulates water efficiently within the system. Correct temperature control reduces energy consumption, saving on heating bills and prolonging system life.

How does zone control work with heat pumps?

Zone control uses thermostats and manifold actuators to heat only occupied rooms to the desired temperature.
This is particularly effective with heat pumps, which operate most efficiently at steady low temperatures and in smaller heating zones, reducing unnecessary energy use.

How long does water underfloor heating take to heat up?

Generally, water UFH systems take 30-60 minutes to reach the desired temperature depending on floor construction, insulation, and thermostat settings. The screeded floors have slower response times than dry systems but offer longer-lasting radiant heat.

What pipe thickness is commonly used, and why does circuit length matter?

Underfloor heating pipes typically come in 12 mm or 16 mm outside diameter. The choice depends on heat load and circuit length:
- 12 mm pipes are usually preferred for shorter circuits or smaller heating zones, offering easier bending and installation but potentially higher pressure drop for long lengths.
- 16 mm pipes accommodate longer circuits with better flow and lower pressure drop.
Shorter circuits are better because water travels a shorter distance, reducing heat loss and pressure drop, improving system efficiency and pump performance. Long circuits can cause uneven heating and increased energy consumption, so it's common practice to split large areas into multiple shorter circuits.

Can underfloor heating work with renewable energy systems?

Yes, underfloor heating is highly compatible with renewable sources such as heat pumps and solar thermal systems, which provide low-temperature heat ideally suited for UFH systems.
Using renewable energy drastically reduces running costs and carbon footprint.

What maintenance does a water underfloor heating system require?

Routine annual servicing includes:
- Checking system pressure is typically 1-2 bar.
- Bleeding trapped air from the system to avoid cold spots.
- Inspecting the manifold, valves, pumps, and thermostats.
- Flushing the system every 3-5 years to remove sludge and add inhibitors protecting pipes from corrosion and limescale.
Maintenance ensures safety, efficiency, and prolongs system lifespan.

How much does it cost to install water underfloor heating?

Installation costs vary by system size, floor type, and manufacturer but generally range from £40 to £70 per square metre. Larger homes require manifold setups, mixing units, and zoning controls, adding to cost. Our combined heat pump and UFH packs offer cost-effective solutions.

Is water underfloor heating suitable for retrofits?

Yes, low-profile and dry systems are designed to install with minimal floor height increase, suitable for retrofits in existing buildings without major construction.
Proper planning and insulation upgrades are essential for best results.

Difference Between PERT and PEXA Pipes in Underfloor Heating

What is the difference between PERT and PEXA pipes?

PERT (Polyethylene of Raised Temperature Resistance) and PEXA (Cross-linked Polyethylene with Aluminum layer) are both commonly used pipes in water-based underfloor heating systems, but they differ in material structure, flexibility, temperature tolerance, and ease of repair.

Flexibility and Bending

PERT pipes are generally more flexible and easier to bend during installation, allowing tighter radii (around 75 mm) without kinking. This flexibility makes PERT pipes easier to install in complex or tight spaces and reduces the need for additional fittings.
PEXA (a type of PEX known as AL-PEX for aluminum barrier) pipes are stiffer and less flexible due to the embedded aluminum layer which provides excellent shape retention but limits bending radius. While still flexible, their bending radius is larger than PERT pipes, requiring careful handling to avoid damage during installation.

Ease of Repair and Handling

PERT pipes, being softer and more pliable, are generally easier to maneuver during installation and are less likely to crack if bent improperly. However, they may be more susceptible to accidental damage if handled roughly.
PEXA pipes, due to their rigidity and aluminum core, are more resistant to deformation but require specialized tools and care during bending and cutting.
Repairing either pipe typically involves cutting out the damaged section and installing push-fit or compression fittings. PERT's flexibility may make temporary repairs easier, but both pipe types have compatible fittings widely available.
Overall, PERT tends to be slightly easier to work with onsite regarding bending and repairs, especially for DIY or retrofit jobs.

Temperature and Pressure Ratings

Both pipe types are suitable for underfloor heating operating temperatures, but PEXA typically has a higher maximum temperature and better oxygen barrier performance due to the aluminum layer.
- PERT pipes commonly withstand temperatures around 60–90°C. - PEXA pipes can withstand up to 95°C and provide superior oxygen diffusion resistance, protecting system components from corrosion.

Which pipe is better for underfloor heating?

Choosing between PERT and PEXA depends on specific project requirements:
- PERT is often preferred for residential underfloor heating due to its greater flexibility, ease of installation, and cost-effectiveness. It is ideal especially in retrofit or smaller projects.
- PEXA is favored in some commercial or higher-pressure systems where its aluminum barrier and higher temperature tolerance add durability and system longevity.
Consulting a professional is recommended to select the best option based on system design, budget, and installer preference.

Summary Table: PERT vs PEXA Pipes

What are the best flooring materials to use with underfloor heating?

Tile, stone, and laminated engineered wood are ideal due to high thermal conductivity.
Vinyl and carpet can be used but require appropriate floor coverings and insulation.
Products like Thermrite Protile provide insulation and can be tiled directly, enhancing efficiency.

Where can I find information about grants for underfloor heating?

Visit our dedicated grants page for up-to-date UK subsidies: UK Energy Subsidies and Grants – FAQ.