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.

The heat input can be controlled by a 7-day timer thermostat which allows you to heat specific rooms or spaces independently, using different settings for weekdays and weekends.

Our thermostats incorporate air and floor sensing controls to ensure optimum operation of the heating system.

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.

When using a boiler as the primary energy source, it is important to note that the minimum area that must be running at any given time is between 60m2 – 90m2.


Installation of a water-based system can be complex due to the intricate design and workings of the system. Because of this 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 they must be part of the main heating system that is installed during construction. 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.


These systems require a certain level of maintenance over the years. The boilers require regular servicing and may need to be replaced after 10-15 years of use. Good quality pipes generally last a very long time.

The overall system is known to exceed thirty to forty years in lifespan and similar to electric floor heating systems, they have an extremely good reputation for providing a high level of comfort with fairly low running costs.

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.


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.

You can select from manual or programmable thermostats or incorporate a mix of the two if you prefer. These thermostats can also 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.

Our trusted partners…

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

We use Bosch condensing boilers for most domestic applications and Baxi boilers for large domestic and commercial applications.

Bosch 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%.

Baxi offers a range of condensing boilers in their commercial boiler range. 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
  • 2-5 year warranty on thermostats

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



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Hydronic Underfloor Heating Installation

In hydronic floor heating systems, water is warmed to 35-45 degrees Celsius using a boiler and circulated at a safe, low pressure through extremely durable plastic pipes laid in or under the floor.

This system typically requires a minimum area of anywhere from 60m² to 90m²  if used with a gas boiler. They are usually installed at the time of construction. They are composed of a network of pipes, valves, manifolds and switches, all of which must work together to heat the zoned areas, although this results in some restrictions when it comes to zoning preferences.

They remain turned on over the period that floor heating is required, providing a constant, gentle heat.

Hydronic Floor Heating IN SCREED

In screed hydronic heating involves the laying of extremely durable piping on top of the slab and insulation in a sand and cement bed of at least 50 mm in depth. 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.

Residential, commercial or industrial
Over any suitable floor structure
Pipe laid over insulation or fixed to surface of structural slab
Additional reinforcement may be required
Minimum 30mm cover to top of pipes (50mm screed bed)
Pipe external diameter of 16mm typically used for residential applications
Pipes connected to manifolds
25 year warranty for Rehau PEX pipes


Hydronic Floor Heating IN SLAB

In slab Hydronic floor heating is a storage heating system. The slab is heated by pumping hot water through pipes that are laid in the concrete slab.

This process can take one to two days at the beginning of the winter season, depending on the thickness of the slab and the amount of floor insulation used.

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.

The heating is controlled using floor and air sensing thermostats that adjust the flow rate of hot water through the pipe circuits.

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.

Residential, commercial or industrial
Slab on ground or suspended slab
Minimum 30mm cover to top of pipes
Pipe external diameter of 16mm typically used for residential applications
Pipes connected to manifolds
25 year warranty for Rehau PEX pipes


Hydronic Floor Heating UNDER BATTENED TIMBER

Hydronic floor heating can also be used under battened timber floors. The pipes are laid over insulation panels and sit directly beneath the floor boards. The pipes run in between the battens, which are typically laid at 450mm centres, and pass through small grooves in the battens to cover the entire floor area.

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.

We recommend using diffusion plates in addition to 25 mm polystyrene insulation beneath the pipes. 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.

System Installation - Hydronic Floor Heating

Residential, commercial or industrial
Suspended timber floors or over concrete slab
Under any suitable timber floor

*Polystyrene insulation is generally recommended at the time of any system installation to minimise heat loss and ensure the highest level of energy efficiency and cost savings.

*It is important to review your state building code before installation to ensure the system complies with current regulations.

Hydronic Floor Heating Insulation

Tacker System

The Tacker System is designed to be placed directly underneath hydronic floor heating pipes to minimise downward heat loss and aid in faster warm up times.

Tacker is comprised of a sheet of expanded polystyrene (EPS) with a laminated fabric reinforced polyethylene based water resistant foil, printed with a grid to help ensure appropriate pipe spacing and fastening.

No water from the screed will penetrate through the insulation when the sheet is taped, because the foil overlaps the sheet and the tape becomes the secondary seal to ensure that no leakage occurs.

The Tacker system complies with the relevant industry standards, is CFC free and has a Class F fire rating.

The standard thickness is 25mm (EPS70) suitable for 16mm hydronic heating pipes and has an R value of 0.65. Sheets are 2.4 x 1.2m for a coverage of 0.35 sheets per m².


Diffusion Plates

The Diffusion Plate System accommodates 16mm heating pipes and uses 0.8mm thick aluminium plates to diffuse the heat over the floor area.

The heat is then transferred through the floor surface into the room. Due to the high conductivity of the plates, the reaction time is lower than traditional screed systems.

This system has been designed for timber joist floors or battened timber floors over concrete slab applications with hydronic floor heating systems.

Insulation is required under a suspended timber floor application and is recommended when installed over a concrete floor.

Size: 1.0m x 0.338m in 0.8 thick Aluminium with 200mm 2-channel pipe spacing. Conductivity 160W/mK. Maximum thickness of wood surface over the diffusion plate: 20mm.

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 except for hard surfaces such as polished concrete. These include tile, stone, terrazzo, carpet, vinyl and timber.

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


Heat Source Options

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:

  • Natural gas (the most popular choice in Australia)
  • Electric heat pump
  • Geothermal heat pump
  • Solar energy

High efficiency condensing boilers are also available and 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%.


  • Wall or floor mounted
  • External or internal with flue to outside
  • Individual or multiple units from 25kW to 150kW
  • Natural Gas or LPG
  • High efficiency condensing boilers
  • 12 month warranty for boilers and manifolds

Gas Boiler Hydronic Floor Heating Systems: The Basic Planning Parameters

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.

Minimum Floor Heating Requirements

Hydronic floor heating systems that use gas boilers must have a minimum area of 60m² – 90m² running at any given time. The area is calculated based on the minimum boiler output. Gas boilers will have a “high” and a “low” gas flame setting and the boiler output will be based on the gas consumption at these two fixed gas settings.

Hydronic floor heating requires a network of pipes, manifolds and controls. It is best to have one zone per room.

This ensures lower running costs and more control over comfort levels, but it can also result in higher upfront costs.


Important Note on Short-Cycling

Heating an area less than 60m² can cause short-cycling which can lead to serious problems with the boiler.

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.


When heating individual small areas such as bathrooms and en-suites, it is important to note that they are not able to be heated on a “stand-alone” basis. It must be part of a larger heated area in order to run efficiently and economically.

If you are looking to heat a bathroom or small living space that does not meet the above minimum area requirements (60m2 – 90m2), the best option is electric floor heating, when taking installation and running costs into account.

Boiler Location

Boilers are typically located inside or outside and mounted to the wall. If they are located inside, they must be flued externally out through the wall or roof. 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.

In Australia boilers are typically located outside, but if a basement or plant room is accessible this would be the preferred location as they offer further shelter from the elements.

An average boiler is around 1m high x 500m width x 350m deep. The boiler must be connected to the manifold(s) with fixed Feed & Return pipes because it is important to keep the distance between the boiler and the manifold to a minimum to avoid unnecessary cost.

Please note that the Feed & Return pipe diameters are generally a minimum of 51 or 58mm in diameter. Allowance MUST be made for this. Typically, they would run through wall cavities attached to the underside of ceilings, run through the floor slab before pouring the concrete, external to the building etc.

Manifold Locations

The manifold is best located in a centralised and accessible location like the linen cupboards, kitchen islands, laundry cupboards, garages, or outside/inside next to boiler. Height and width restraints should always be considered before installation.

The floor heating water pipes connect directly to a manifold, so it is important that the manifold be located within proximity to the heated area. Typically, the maximum area serviced by a single manifold is 240m².

The manifold not only has to be at the highest point of the areas connected to it, but it must be located within close proximity to those zones.


Hydronic Floor Heating Systems, A Basic Design Guide

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.

A high efficiency condensing natural gas boiler is an economically sustainable energy source used to heat the water that flows through the piping of a hydronic floor heating system.

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.

In practical terms, the minimum area that can be heated by hydronic floor heating system is 30m2. Electric floor heating can allow total flexibility and is size independent.

With the popularity of hydronic floor heating systems continuing to grow, there are a number of installation and design requirements to be aware of before specifying this type of system.

For the purposes of this article, we will focus on the fundamental planning requirements including:

  • Types of Systems
  • Manifolds/Minimum Heated Area
  • In screed installations
  • In slab installations
  • onto the top surface of the bottom layer of reinforcing slab steel
  • on top of a single layer of reinforcing steel
  • to the underside of the top layer of the slab reinforcing steel


Types of Systems:

The 2 most common systems used for the installation of a Hydronic floor heating system are In Slab and In Screed.

In Slab

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.

In Screed

The heating pipe is 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). 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. This insulation system tends to be more expensive than the above mentioned In Slab insulation systems.

An In Screed system adds a total of 80mm height to the finished slab height (Insulation 30mm + screed 50mm, includes the pipe).

Manifolds Location and Minimum Space Requirements:

Manifolds are best located centrally to the circuits they are feeding. Manifolds will vary in size according to the number of pipe circuits required. Typically, manifolds are located in cupboards, storage areas, kitchen islands etc. Minimum space required is 600mm H x 500mm W x 150mm D and the maximum is 600mm H x 1000mm W x 150mm D.

Diagram: Circuits connecting into the bottom of the manifold:

The manifold 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.

Although it is possible to have the circuits situated above the manifold, it is not recommended due to the risk of trapped air that can cause inefficiencies and noise issues.

Recommended Energy Sources:

Condensing Gas Boilers

Gas Boilers (natural or LPG) may be located indoors or outdoors at a cost starting at $2,500 plus installation. Fluing may be required for indoor installations and boilers should be located as close to the manifolds as is feasible to minimise installation costs. Natural gas is the lowest cost option of these two gases.

Electric Heat Pump

Electric Heat Pumps are commonly used, but will add $10,000 plus to the base cost for the system and will typically only handle around 150 m² of heated area. This energy source is, however, usually the most cost efficient option.

Installation Methods for Hydronic Piping:

Installation of the pipes on top of a single layer of reinforcing steel

Following the installation of the single layer of reinforcing steel, the pipes are secured onto the top of the steel layer.


  • The concrete cover above the pipes must be a minimum of 30mm.
  • The pipes must be located no deeper than 60mm of the finished slab surface unless there is a minimum of R1.8 insulation between the slab.
  • The variation in the depth between the highest and lowest placed pipe must not vary more than 20mm from the finish floor surface.

Installation of the pipes onto the top surface of the bottom layer of reinforcing slab steel

Following the installation of the first layer of reinforcing steel, the pipes are secured on top of the steel, before installing the second layer of reinforcing steel.


  • The slab must have a minimum of R1.8 insulation directly below the slab.
  • The variation in the depth between the highest and lowest placed pipe must not vary more than 20mm from the finish floor surface.

Installation of the pipes to the underside of the top layer of the slab reinforcing steel

This installation option is typical for suspended slabs where the maximum cover over the top reinforcing steel is limited to less than 45mm.

For this installation, the lower reinforcing steel layer must be fully installed to start. The hydronic pipes are then temporarily secured to the top of this lower steel layer.

The upper steel is then installed and once in place, the hydronic pipes will be unsecured from the lower steel, lifted and permanently secured to the underside of the top steel.

This option requires significantly more installation labour and there is a risk of damage to the pipes when the top steel reinforcement is laid over the pipe.


  • The concrete cover above the pipes must be a minimum of 30mm.
  • The slab must have a minimum of R1.8 insulation directly below the slab.
  • The variation in the depth between the highest and lowest placed pipe must not vary more than 20mm from the finish floor surface.

**Upper Steel Layer Placement – It is essential with this option, that no steel is placed over the pipes while in their temporary location and that no steel will impede a straight vertical lift of the pipes from their temporary location on the lower steel to their permanent location on the underside of the top steel.



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