Hydronic Underfloor Heating

Why Hydronic Underfloor Heating?

Hydronic underfloor heating is an energy efficient and sustainable solution for heating your home. It works well under several different floor surfaces including marble, stone, slate, carpet, timber and all varieties of tiles.

Hydronic underfloor heating is a central heating system and is designed to run continuously during the (winter) heating season. It is not designed for occasional “demand” heating. Where greater heating flexibility is required, particularly for small areas such as bathrooms, en-suites, laundries etc., electric floor heating is recommended.

Hydronic floor heating has become an attractive and regularly specified upgrade for a wide range of applications, especially when paired with a high efficiency condensing natural gas boiler. These systems are quite sophisticated in design and consist of warm water that circulates through an intricate network of polyethylene oxygen-resistant piping under the floor surface. This ensures a gentle, warm heat that is evenly distributed throughout the entire living space


Hydronic floor heating is a great option for large, open entertaining areas and it works well under cold floor coverings such as marble, stone, slate, polished concrete and all varieties of tiles.

It’s also fabulous under carpet and timber floors, however you need keep in mind that there are particular standards and temperature restrictions that must be met when using these floor coverings.


These systems require a certain level of maintenance over the years. Boilers require regular servicing and may need to be replaced after 10 years of use. Good quality pipes generally last a very long time (25-year warranty for Rehau pipes).

The overall system is known to exceed thirty to forty years in lifespan. On top of the fairly low running cost, this can give owners a high return on investment when measured against other heating solutions on the market. Learn more about our Hydronic Extended Warranty Agreement.


Hydronic floor heating can be very economical to run, however, the upfront costs tend to be higher than electric systems, because of the sophistication and intricacy of the design, as well as the skilled labour that is required to perform a proper installation.

A significant part of a hydronic floor heating costs is fixed, meaning it remains similar whatever the size of the area to heat. A gas boiler is an example of a fixed cost that hardly changes when the size of the surface to heat increases. For this reason, the bigger the surface, the cheaper the rate per m2 is. This is an important difference with Electric Floor heating, where the rate per m2 remains the same as the surface to heat increases. This is the reason why hydronic floor heating (HFH) is a more and more interesting proposition than Electric Floor Heating (EFH) as the area to heat increases, and we would recommend to go for HFH over EFH for surface over 60m2.


Another factor in the efficiency of your floor heating system is a high quality thermostat. This will allow you to heat specific rooms independently and program them to meet the needs of your lifestyle.

Because hydronic floor heating is a central heating system, we recommend non-programmable thermostats for your installation. These thermostats can be linked to your home automation systems.

A good quality thermostat will give greater control over temperature, zoning and timing, allowing you to make the most out of your floor heating system.


Installation of a water-based system can be complex due to the intricate design and workings of the system. It is important to seek out a licensed professional to do the job.

Hydronic floor heating systems are normally only used in new projects because it is easier to install into the slab. In some circumstances these systems can be used in retrofit projects, but only in a screed bed that is at least 50 mm in depth (ideally 80mm). As this is a significant height, some customers prefer to go for electric floor heating for renovations.

In hydronic floor heating systems, water is warmed up to 50 degrees Celsius and circulates at a safe, low pressure through a network of pipes, valves, manifolds and switches, all of which must work together to heat the zoned areas:

It is a closed system, which means that the water that is introduced the day the system is commissionned is most likely to be the same for the rest of the life of the hydronic system. For this reason, it is crucial to select the best quality for the manifolds, pipes, boilers and anything that will be in contact with the water, because any inpurity will worsen over time.

Our trusted partners…

Our partners are long-standing, industry recognised leaders that contribute efficient, high quality products to our hydronic floor heating systems.

Baxi boilers for domestic and commercial applications. Baxi boilers use condensing technology for a high level of efficiency. The waste heat is recycled instead of being expelled through the flue system like in a non-condensing boiler. This results in efficiencies of over 90%.

We also use a range of Danfoss manifolds and controls and Rehau pipe. We have accredited Rehau installers available for service and repair.

Many of our parts are imported from leading European manufacturers that meet all relevant Australian standards and are backed by the following warranties:

  • 25-year warranty on pipes
  • 2- to 5-year warranty on thermostats
  • 2-year warranty on manifolds
  • 2-year warranty on boilers

So whether you’re building a new home or carrying out an extension or renovation, Devex Systems has a hydronic floor heating solution that is right for you!

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Heat Source

Hydronic heating keeps running costs down by allowing a choice of energy sources, since the water can be heated by a range of energy efficient and environmentally friendly options.

Gas boilers are typically used, with other options including high efficiency electric heat pumps, geothermal heat pumps and solar energy.

Heat Sources:

  • Gas Boilers (Natural gas or LPG)
  • Electric heat pump
  • Geothermal heat pump
  • Solar Collectors

We recommend to use a gas boiler with natural gas as a first choice as the up-front cost is much lower than heat pumps while having similar running costs, and it is more reliable than solar collectors. However if your property cannot be connected to natural gas, heat pumps can be an interesting option depending on your budget.

Gas Boilers

High efficiency condensing boilers are recommended as they have a higher efficiency than gas boilers and have far lower emissions.

A condensing boiler recycles the heat that is typically lost in the exhaust of a non-condensing gas boiler. Additionally, much of the exhaust emissions are condensed and discharged into the sewer system.

Condensing boilers typically have efficiencies of 95% or more compared with non-condensing gas boilers at around 70-80%.

There are several things to keep in mind when installing a hydronic floor heating system that uses a gas boiler: minimum heated floor area requirements, manifold and boiler locations and zoning layout.

Boiler sizing

We use Baxi boilers which size ranges from 12kW to 110kW. As we design our system to 100W/m2, it is easy to determine the size of the boiler you’ll need: for example, for 110m2 to heat, you’ll need 11kW of power, so you’ll go for the 12kW boiler (minimum size).

Minimum Floor Heating Requirements

A boiler has a maximum as well as a minimum output (related to a “high” and a “low” flame – similar to a gas cooker). The maximum output is usually within the name of the boiler. For example, the Baxi Luna Duo-Tec GA 1.12 has a maximum power output of 12kW. The minimum output is also an important data because it determines the minimum floor heating requirement. For example, the Baxi Luna Duo-Tec Ga 1.12 has a minimum power of 2.2kW. The bigger the boiler, the bigger the minimum output.

Gas boilers are designed to run for periods of time (5 min or more) and where their capacity significantly exceeds the heat load of the floor, the boiler will run on a rapid repeat ON/OFF cycle (called “short cycling”) which can cause significant damage to the boiler through running and maintenance issues.

For this reason, we prevent in our system for a heating zone less than 22m2 to be able to turn on the boiler. This is why bathrooms, ensuites or other little areas won’t be able to be heated on a “stand-alone” basis and they must be part of a larger heated area in order to run efficiently and economically. This is one of the reasons why we recommend electric floor heating for such rooms in case you would like them to be heated while the mains system is off (for example, having a warm floor in the bathroom after a shower during Spring while the whole system is off).

Boiler Location

Boilers are typically mounted on the wall, inside or outside. If the boiler is located inside, it must be flued externally out through the wall or roof. If it is located outside, it has a special case to protect it from the weather that makes it bigger, and it is usually more visible, but on the other hand, this is a cheaper solution as there is no flue to install. Also during the design phase for the location of the boiler, it is important to keep in mind that the maximum flue length is limited. Keeping the fluing distance down is a very important factor in keeping the overall costs down. An average boiler is around 700m high x 400m width x 350m deep.

Boiler type

Boilers for hydronic floor heating can be used for your Domestic Hot Water (DHW) system as well. A boiler that is connected to both the heating system and the DHW system is called a combi boiler. The boiler is usually connected to the heating system, but as soon as there is demand for hot water (from a tap or shower for example), the boiler power switches to the DHW system and gives it all its power. Unless the demand for hot water from the DHW system lasts more than a few hours, this won’t affect the heating system at all thanks to the thermal mass of the slab or the screed.

The power output of a combi boiler for the DHW system depends on its size. It is important to note that this is an instantaneous hot water system and as such, it provides limited supply of hot water. For example, the output of the Baxi Luna Duo-Tec boiler is 9.8 litres/min. A standard efficient head shower consumes 9 litres/min so it means that you’ll be able to run no more than 1 shower at a time with this boiler.

A combi boiler can be a good solution to connect a room (for example, a laundry or a bathroom) that is far away from the DHW tank, but close to the hydronic boiler to avoid long pipe connections and waiting time when turning on hot water.

Heat Pumps

Heat pumps are an interesting option if there is no natural gas supply to your property. Heat pumps are actually more cost effective to run than gas boilers due to their high efficiency (around 400% for heat pumps versus about 100% for gas boilers). Depending on your location, gas is on average 3 times cheaper than electricity so it makes heat pumps 30% more economical than gas boilers).

However, the upfront cost of heat pumps is usually a killjoy for many customers. On average, you can expect heat pumps to be 6 times more expensive than gas boilers.

Solar Collectors

Not to be mistaken with PV solar panels, solar collectors are tubes in which water is running to collect heat from the sun. This is ideal to use when you have a hydronic floor heating system because you don’t need any expensive energy conversion, contrary to PV solar panels, where a heat pump is necessary to convert electricity to hot water.

Solar collectors are ideally used along with a domestic hot water (DHW) tank so that the heat taken from the sun is used for both the DHW system and the heating system.

Feed Pipes

Feed pipes run from the boiler to the manifolds. They can be installed in different way, depending on your building. They can run under the steel mesh, or through the wall or/and the ceiling. If they are meant to be in the concrete slab or hidden in some other way, we usually use flexible PEX pipes. Otherwise, for visible pipes, we would use copper pipes. Those are more expensive and more time consuming to install, but give a better looking finish.

Feed pipes are insulated to prevent any heat loss. We put the PEX pipe into a conduit to create an air pocket that insulated the feed pipes (using the same principle as double-glazed windows). Or, in the case of copper, we wrap the feed pipes with thick insulation.

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Manifolds are essentially hubs to which all circuits are connected. The manifolds distribute the water to each circuit and the regulation of the heating is done through actuators that start and stop the flow within the circuits. All actuators are commanded by floor sensing thermostats.

Manifolds can be mounted with a mixing shunt that is used to mix the return cold water with the supply water to decrease the temperature of the supply water temperature. This is used for hybrid system that have both radiators (that work at 80deg Celsius) and floor heating (that needs to work at 50deg Celsius maximum).

Manifold Location

Manifolds are best located centrally to the circuits they are feeding and in an accessible location such as the linen cupboards, kitchen islands, laundry cupboards, garage or outside/inside next to boiler. Height and width restraints should always be considered before installation. Manifolds will vary in size according to the number of pipe circuits required.

Manifolds preferably should be situated at the highest point in those circuits connected to it. This means that if you are heating two levels of your home, it is best to have a manifold at each level so that the circuits at each level can be connected into the bottom of the manifolds.

Number of manifolds

Manifolds from Danfoss can have between 2 to 12 heads. There are as many heads as there are circuits. For 16mm heating pipes, a circuit can heat around 20m2. It means that for surfaces to heat more than 240m2, you will need more than 1 manifold.

Manifold Dimensions

* Where there is a horizontal space limitation

The minimum height required is 600mm. The minimum width is as follows:

*Where there is a vertical space limitation

The minimum height required is 450mm. The minimum width is as follows:

Heating Pipes

There are three possible ways to install the heating pipes: directly in the slab, in the screed or using diffusion plates.

In all cases, Devex Systems is using Rehau PEX pipes that come with a 25-year warranty.

Hydronic Floor Heating in slab

In-slab hydronic floor heating is the most popular way of installing hydronic floor heating. It is a storage heating system that uses the thermal mass of the slab to store heat. It makes the heating system very slow to respond (it can take one to two days to heat up the slab, depending on the thickness of the slab and the amount of floor insulation used), but is more economical to run, especially with insulation.

Once the slab is heated through, it radiates heat from the floor upwards into the room, creating a comfortable and gently heated environment with no draughts, dust or noise.

We recommend extruded polystyrene insulation beneath the slab and on exposed slab edges to minimise system heat loss and ensure the highest level of energy efficiency and cost savings.

The heating pipe is located on top of the mesh of the slab and requires a minimum of 30mm of concrete cover over the top of the piping. Other options may apply when slab steel reinforcing design will not allow hydronic pipes to be placed over the top steel.

All slabs must be insulated beneath and around the edges of the heated area to prevent downward heat loss and optimise energy and cost savings.

Hydronic Floor Heating in screed

For this configuration, the heating pipes are located onto the top of the finished slab and requires a minimum of 30mm of concrete cover over top of the pipes (therefore a minimum screed depth of 50mm).  This is covered by a suitable floor surfacing such as marble, stone, slate and all varieties of tiles.

This system is generally faster acting than an in slab system. Similar to other systems, it radiates heat from the floor upwards, creating a comfortable, gently heated environment with no draughts, dust or noise.

The heating is controlled using floor or air sensing thermostats that regulate the flow of hot water through the pipe circuits.

We recommend insulation that can be installed on top of the finished slab with the water pipes attached directly to the insulation.

The installer would supply and install the appropriate insulation materials beneath and around the edges to, again, prevent downward heat loss.

Hydronic Floor Heating in diffusion plates

Hydronic floor heating can also be used under battened timber floors using diffusion plates. The diffusion plate system consists of aluminium plates with preformed grooves to take the pipe. The aluminium plates transfer the heat away from the pipes giving a uniform heat distribution beneath the timber floor and enabling a more efficient heat transfer to the timber floor. The pipes sit directly beneath the floor boards.

The heating is controlled using floor and air sensing thermostats that adjust the flow rate of hot water through the pipe circuits. The thermostats are typically set to a maximum floor temperature of 27°C to ensure the timber is not over-heated.

Hydronic Floor Heating Insulation

XPS Insulation

The XPS (Extended Polystyrene) Insulation Sheets from Foamular are designed to be placed directly underneath hydronic floor heating pipes to minimise downward heat loss and aid in faster warm up times.

The standard thickness is 25mm suitable for 16mm hydronic heating pipes and has an R value of 0.89 m2·K/W. Sheets are 2.4 x 0.6m (=1.44m²) for a coverage of 0.70 sheets per m². We also offer 30mm thick sheets (for a R value of 1.07 m2·K/W) and 50mm thick sheets (R = 1.78 m2·K/W).

Quick Heat

The Quick Heat system is ideal for batten timber. It is a combination of diffusion plates and insulation sheets. The insulation sheets are placed directly underneath the aluminium diffusion plates, minimising downwards heat loss.

Solar Integration – Solamander® Hydronic Energy Hub

Hydronic Underfloor Heating is compatible with, the Solamander Hydronic Energy Hub. This system prioritises renewable energy sources (solar, wetbacks) over non-renewable energy sources (heat pumps, gas boilers) for a variety of energy uses including hydronic floor heating, pool heating, radiator heating and domestic hot water.

The prioritisation of renewable energy sources like solar power reduces the energy costs associated with domestic hot water and other heating related utility bills.

Hydronic Energy Uses:

  • Domestic Hot Water (DHW) – delivered via a buffer storage tank with a heat exchange coil to transfer energy to the water in the tank when incorporated into the Solamander® system, or as instantaneous DHW on other hydronic systems.
  • Pool/Spa Heating – delivered via a titanium plate heat exchanger to the pool and/or spa. A heat dump (for energy that cannot be used or stored) is required for the system where solar energy is being harvested and a swimming pool is not available.
  • Hydronic Radiator Heating – with appropriate feed pipe distribution and zone control.
  • Hydronic Floor Heating – with appropriate feed pipe and manifold systems and zone controls.

Our partner brands, including Danfoss controls and Rehau pipe are recommended, however, other systems can be integrated with Solamander®, as long as they are appropriately installed and configured.

The Solamander Hydronic Energy Hub achieves an optimum and pleasant indoor environment with comfort heating on demand throughout the year.

This system has been designed by Devex Systems as an environmentally sound and sustainable solution that offsets household greenhouse gas emissions and allows residential home owners to get one step closer to a carbon neutral house.

Alternative Hydronic Heating Options:

  • Radiators only or radiators integrated with hydronic floor heating. These can be integrated with Solamander® or installed as an independent system.
  • Domestic Hot Water (DHW) and/or pool heating options can be integrated with hydronic heating. Where the Solamander® system is installed then DHW is best when included with it.
  • Thermal insulation on an existing slab can have the floor heating pipes fixed to the insulation to heat a screed or topping slab floor and so reduce the downward heat losses.
  • A mix of heating requirements on multiple building levels is commonly combined into the one system.
  • Multi-users can be connected together from the one heat source with or without Solamander®. When there is more than one occupant being billed for the usage, separate metering of the hydronic heating use can be provided.


Solamander® options:

The basic Solamander® system incorporates solar energy capture with hydronic floor heating and Domestic Hot Water (DHW), and at least one other heat source to ensure that you will never run out of hot water.

Solar controls are exacting and detailed to ensure that the solar energy capture is efficient and effective. The Solamander® controller ensures automatic protection of the home occupants against growth of water borne bacteria and for the safe operation of all elements of the system.

For these reasons we only include the capture of solar energy with the Solamander® control system. Other heat uses and heat sources can be added to or swapped over with the Solamander® system at any time in the future, simply by plumbing it in and telling the hydronic energy hub controller what changes have been made. This future proofs your investment.

When a Solamander® system is installed the DHW should always be incorporated with it because DHW is needed throughout the year and is the first priority for solar/wetback heating.

The inclusion of under floor hydronic heating provides the added value of being able to appropriately store into the floor any excess renewable heat energy that has been captured which is not needed for DHW.

Summer time heating is primarily used to maintain the DHW with excess heat passed through to supplement pool heating needs.

Floor surfaces:

Hydronic underfloor heating can be installed under a variety of floor surface finishes including tile, stone, terrazzo, carpet, vinyl and timber to name a few.

While each has its own specific requirement, timber needs to comply with the flooring supplier’s specifications to ensure that the timber surface is appropriate for under floor heating and that the controls will allow the setting of protective limits appropriate for each timber floor.

Retrofitting existing areas:

Renovations can also have various forms of under floor heating installed. Hydronic heating is typically included in a 50mm (minimum allowable thickness) screed bed on top of a concrete slab or fiber-cement sheet floor of an existing building.

For more information on the Solamander Hydronic Energy Hub, please CLICK HERE

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