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Floor heating, explained · Perth

Thinking about floor heating? Here's what nobody tells you before you build.

Hydronic floor heating warms a home from the floor up – warm floors, no blown air, no noise, low running cost. When it's built right.

The part almost nobody mentions: it can also be built wrong, and a wrong system is buried in concrete where you can't fix it. Both look identical the day you sign. You find out which one you got in July, when the first bill lands.

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Free, and it takes a minute. From the Perth engineers who design these systems and install them with our own team, since 1992.

Modern kitchen with hydronic-heated polished concrete floor, marble island and timber cabinetry, East Fremantle

East Fremantle – hydronic floor heating beneath polished concrete

How it works, in 30 seconds

Warm water under the floor. The whole floor becomes the heater.

Hydronic just means warm water moving heat through your home.

  1. A heat pump outside heats the water. Warm, not hot – about 25–40°C, cooler than your hot tap.
  2. The water runs to a manifold – the box where every pipe loop starts and ends, and where each room's flow is set.
  3. It flows through loops of pipe buried in the screed under your floor – the concrete-like layer poured over the main slab, under your tiles or timber.
  4. The whole floor becomes a large, gentle, low-temperature radiator. The room warms from the floor up.

Because the heat starts at the floor, it stays low in the room, where people are – instead of collecting at the ceiling like blown air. Gentle, even, radiant warmth: no fan, so no blown air and no dust kept moving around the room, no noise, and nothing on the walls.

Where the warmth ends up

Same room, same cold night. The difference is where the heat goes in.

A room heated by a split system Warm air blown from a wall unit rises and collects under the ceiling. The air near the floor, where the person is, stays cool. Warm air collects at the ceiling Cool at the floor, where you are
Split system or ducted airIt heats the air. Warm air rises and stratifies – warm at the ceiling, cool at the floor – so you turn the thermostat up to feel warm.
The same room with hydronic floor heating Warm water in pipes under the floor warms the whole floor. Warmth rises gently and evenly from the floor, strongest where the person is standing, and a touch cooler at head height. A touch cooler at head height Warm water in pipes: the whole floor is the heater
Hydronic floor heatingThe warmth starts at the floor, where you are, and the air at head height stays a touch cooler – the reverse of aircon.
The thing to understand first

Same house. Two ways to build it. Two and a half times the bill.

Take one home, 200 m². Build the heating the careful way – insulated screed, sized to the rooms, heat pump that can breathe – and it runs at about $240 a month through a Perth winter. Build it the fast, cheap way most installers quote – pipe dropped in an uninsulated slab, no thermal break – and the same house runs at about $601 a month.

Built rightInsulated screed, sized correctly ~$240/mo
Built the common cheap wayPipe in an uninsulated slab, no thermal break ~$601/mo

Modelled estimate, not a promise: a 200 m² home, per month of the five-month Perth heating season (May–September), at Synergy's A1 rate of 33.26 c/kWh (July 2026). Your number depends on your home.

Same comfort. Same winter. More than double the cost, for the life of the house. And the cheaper version is the one you'll usually be quoted, because it's faster to pour.

What's different is under the floor

Built right: pipe in an insulated screed Cross-section from the top: floor finish, a screed with the heating pipes set in it, an insulation board, then the structural slab on a membrane over sand. Insulation also runs down the full depth of the slab edge. The heat goes up into the room. Heat goes up, into the room Outside Floor finish Screed with the heating pipes Insulation board Structural slab Membrane, then sand Edge insulation down the full depth of the slab edge
Built right: pipe in an insulated screedInsulation under the screed and down the slab edge, so the heat goes up, into the room.
The common cheap way: pipe in an uninsulated slab Cross-section from the top: floor finish laid straight on the structural slab, with the heating pipe tied to the reinforcing mesh inside the slab. There is no insulation under the slab or at its edge. Some heat goes up into the room; the rest goes down into the sand and sideways out through the slab edge. Only part of the heat goes up Outside Floor finish Structural slab, pipe tied to the mesh No insulation under it or at the edge The rest goes down, and out the edge
The common cheap way: pipe in an uninsulated slabNothing under it or around its edge. Some heat goes up; the rest soaks down into the ground and out through the slab edge.

Screed: the layer of concrete-like topping the heating pipes are buried in, poured over the main slab and under your floor finish. Thermal break: a strip of insulation that stops the warm slab touching anything cold – the slab edge, a path, an alfresco.

Contemporary living area with marina view and polished concrete floor, East Fremantle hydronic floor heating
East Fremantle – hydronic floor heating by Euroheat, under polished concrete.
Where the money leaks

Three holes you can't see

70%

The slab eats the heat

Pipe in a slab with nothing under it or around its edge: in the worst cases, up to 70% of the heat you pay for goes into the ground and the structure, not the room. You're heating Perth.

2–3×

Thermal bridges drain it

Where the warm slab touches something cold – an edge, a path, a pool – heat pours out. One ignored bridge can double or triple the bill.

50%

A boxed-in heat pump chokes

The heat pump needs to breathe outside air. Hide it in a garage or fence it in tight and it loses up to half its efficiency.

None of it shows in a quote. All of it is decided before the pour. All of it is permanent after.

Not a knock on plumbers

This isn't about plumbers being dishonest.

Most aren't. It's that hydronic isn't plumbing – it's building physics. A standard installation covers the physical steps – laying the pipe, connecting the manifold, fitting a heat source, pressure-testing – not the engineering that makes those steps count.

The running cost is decided by the calculations before the pipe: the heat load (how much heat each room loses on the coldest night), sizing, siting, thermal breaks, controls tuned to the slab.

By our count, around 95% of WA installers don't really understand these systems – not because they're crooks, but because the calculation step isn't part of laying pipe. So even an honest plumber quoting in good faith quotes you the cheap house, because the engineered house isn't the thing they do.

That is why the calculation and the install should sit with one team. We're engineers who design every millimetre, install it ourselves, and stand behind it.

Free guide

You Find Out in July

The five floor heating mistakes that are invisible in a quote, permanent in a slab – and how to avoid every one.

Phil Pacak wrote this guide after more than 30 years of seeing the same mistakes buried in slabs across WA. 27 pages. Real physics, real numbers, no marketing fluff. If you're building in the next 12 months, read this before you sign a quote.

What's inside:

  • Why up to 70% of your heat can disappear into the ground – and the one detail that stops it
  • The slab calculation that most plumbers skip (and what it costs you every month for 20 years)
  • How a badly placed heat pump can lose up to half its efficiency before it ever heats a room
  • Thermal bridges: the invisible drains that can double or triple your bill
  • What "it still produces warmth" actually means – and why it's the most dangerous half-truth in hydronic heating

The same guide that's been the starting point for most of our best clients. Download it and you'll know more about hydronic floor heating than 95% of the people quoting it.

Get the free guide → Or go straight to the calculator

27 pages on the five most common floor heating mistakes. Free – enter your email and it opens straight away.

Building later?

The heating decisions you have to lock in – and exactly when.

Every expensive heating mistake has a closing window, and the earliest ones close before the plans are final. The one-page timeline shows all four build stages – design, pre-slab, first fix (pipes and cables in, walls still open), pre-handover – and which decisions are permanent the moment the concrete goes down.

See the one-page timeline →
Watch

Hydronic against electric floor heating: the running cost

Three and a half minutes from Phil on why a heat pump runs hydronic heating for about a third of what electric floor heating costs. Recorded in 2019 – the rates have moved, the physics hasn't.

More videos – heat pumps, zoning, pool heating, building regulations – on the Videos page. Straight answers to the questions people ask most: Questions answered.

Start with one question: can your home even have it?

The two houses look identical the day you sign, and stay that way for a winter or two – then one of them quietly starts costing far more, and by then the concrete has set.

If you're building new, you're in the best possible position to get the right one – if you make the decisions early. If it's an existing home, there's a different path to the same quiet, even warmth. Two minutes tells you which one you're in.

Can your home have floor heating? → Or see the gap for your home