How to Keep Your Bathroom Warm in Winter: Heating Options, Compliance and What to Specify Before You Renovate
Most cold bathrooms in Australian winter are a combination of two problems: not enough heat, and too much moisture sitting on cold surfaces. Fix one without the other and you’ve halved the problem, not solved it.
This guide covers the main heating options for a bathroom renovation — electric underfloor heating, heated towel rails, radiant ceiling heat, and combination exhaust units. What each one does, where it belongs, what it costs in NSW and ACT, and what the compliance requirements look like.
Here’s what to know before you specify.
Why a Cold Bathroom Is a Specification Problem, Not Just a Comfort One
Cold is the symptom. The underlying problem is usually a combination of missing heat sources, inadequate ventilation, and condensation building up on tile surfaces that haven’t had a chance to warm up. When those three things coincide — and in older Australian bathrooms they usually do — heating alone doesn’t fix it.
Condensation on tile surfaces isn’t just uncomfortable. Water sitting on grout lines, at silicone junctions, and behind poorly sealed edges slowly works at the waterproofing underneath. Not dramatically, and not quickly. But bathrooms where condensation is chronic tend to show grout failure, mould at the bath-to-wall junction, and eventually water getting behind the tiles. The tile is usually fine. The substrate and membrane aren’t.
The NCC references AS 1668.2 for minimum exhaust requirements in wet areas — 25 L/s extracted to outside the building. That’s not a guideline. It’s a compliance requirement. A bathroom that doesn’t meet it is likely developing the conditions that make it feel perpetually cold and damp even when a heat source is running. Warm humid air that can’t escape condenses when it hits cold surfaces, and the cycle repeats.
Before specifying heating, confirm the ventilation is actually doing what it’s supposed to do. If the exhaust fan is underpowered, ducted into the ceiling cavity rather than outside, or simply dead — that’s the first fix. Adding heat to an improperly ventilated bathroom is expensive guesswork.
Related: Ventilation requirements in wet areas connect directly to waterproofing compliance under AS 3740. See our AS 3740 waterproofing compliance guide ›
Bathroom Heating Options — What Each One Does and Where It Belongs
The options differ in installation complexity, cost, and whether they’re providing primary or supplementary heat. Knowing which you need before anything is ordered saves the conversation you don’t want once trades are on site.
Resistance mat or cable system installed under the tile bed. The most common heating specification for a residential bathroom renovation in NSW and ACT. Requires a licensed electrician and typically a dedicated circuit. Works with most tile substrates provided the adhesive type is correct — confirm compatibility with the mat manufacturer before the tiler quotes.
Hot water circulated through pipes set into or under the slab. More efficient to run over time, but the install cost is significantly higher and it needs to integrate with your hot water system. Practical at the new build stage or a whole-house renovation. For a standalone bathroom upgrade, electric is the right answer almost every time.
Supplementary heat, not primary. The number of bars isn’t the relevant specification — wattage is. A 150W rail in a 12m² bathroom is a towel warmer. If the goal is warm air, confirm the wattage is appropriate for the room volume before ordering. Hardwired is the correct installation for a renovation; plug-in variants belong at a hardware store, not in a tiled bathroom.
Infrared panels or radiant ceiling heaters deliver fast surface warmth rather than gradually heating the air. No moving parts, low maintenance. In a wet area the IP rating matters — IP44 minimum for proximity to shower zones. A solid supplementary option in larger bathrooms or where underfloor heating wasn’t included in the original brief.
Combination units — IXL Tastic and equivalents — handle ventilation compliance and add convective heat in a single fitting. A practical choice for small bathrooms where one fitting does both jobs. Check the heat element wattage, not just the exhaust rating. Product packaging tends to lead with sone ratings (noise) and bury the airflow and wattage specs in smaller print.
Underfloor Heating in Bathrooms — Electric vs Hydronic, Substrates and What It Costs
Electric underfloor heating in a bathroom is a decision that gets made at the tile substrate stage, not after the tiles are laid. The mat — a thin resistance cable or mesh — sits between the substrate and the tile adhesive bed. Once tiles are down, it’s down. Getting the specification right before tiling starts is the only time it’s straightforward.
Electric vs hydronic comes down to context. Electric is the right choice for a standalone bathroom renovation — lower install cost, no plumbing integration required, and running costs are manageable when it’s on a programmable thermostat and used seasonally. Hydronic is worth considering if you’re already specifying radiant floor heating across the rest of the house. As a retrofit in a finished bathroom? The cost and disruption make it the wrong answer almost every time.
Tile thickness and format affect performance. Thicker tiles have higher thermal mass — they take longer to reach temperature but hold heat longer once they’re there. Large-format tiles (600×600 and above) distribute heat well across their surface area. Mosaic works too, but the higher proportion of grout lines reduces the effective heated area slightly. Polished large-format porcelain on a correctly installed heated mat is about as good as bathroom floor heating gets.
Adhesive selection is where failures happen. Electric mats require adhesive compatibility — most standard cement-based adhesives are suitable, but flexible adhesive is required wherever large-format tiles are specified, which on a heated floor is almost everywhere. The mat must not run across movement joints or expansion joints in the substrate. That’s not a preference — it’s a failure point. The thermal expansion cycle stresses the cable, and the system fails. Confirm the layout with both the mat installer and the tiler before either starts work.
Installation requires a licensed electrician (Class 1 in NSW). A dedicated circuit is standard practice and generally a manufacturer warranty condition — if the switchboard doesn’t have capacity, an upgrade is part of the project cost. That belongs in the quote before work starts, not as a day-of discovery. For the thermostat: programmable with a floor sensor is the current standard. The sensor position needs to be set before grouting. Moving it afterwards means breaking tiles.
Cost ranges: electric mat supply runs $80–$200 per m² depending on brand and system type. Electrician installation for a standard bathroom layout: $300–$600. Thermostat supply and installation: $150–$400. A typical 4–6m² bathroom comes to $800–$1,800 installed. Substrate levelling is separate if required. Board upgrades are separate if required. Get all of it in one scope before signing off on the quote.
Related: Underfloor heating specification interacts directly with tile adhesive and substrate requirements. See our bathroom tiles guide for adhesive and substrate specification ›
Heated Towel Rails and Supplementary Heating — Specification, Sizing and What People Get Wrong
A heated towel rail is not a bathroom heater. That’s not a knock on the product — it does what it’s designed to do. The problem is when it gets specified as the answer to a cold bathroom, which happens more often than it should, usually when heating isn’t explicitly discussed during the renovation consultation and everyone assumes someone else covered it.
Hardwired vs plug-in: hardwired is the correct installation for a permanent fitting in a renovated bathroom. Plug-in units require a visible power cord running across a wet area — fine for a temporary arrangement, not appropriate as a finished installation. Hardwired requires a licensed electrician. That adds cost relative to a plug-in unit. It also adds compliance, a clean finish, and removes the cord.
Sizing by wattage, not bar count. A working figure for supplementary heating is 30–40W per cubic metre of room volume. A standard 4m × 2m × 2.4m bathroom has a volume of roughly 19m³, which needs somewhere between 570–760W for a meaningful supplementary heat contribution. Most residential heated towel rails are 150–300W. In a room that size, they warm the towels and add a marginal ambient contribution. In a powder room or very small ensuite under 6m², that contribution is more meaningful. In a full bathroom, plan accordingly.
Placement matters more than people usually think. Don’t put the towel rail directly in the airflow path of the exhaust fan — a poorly placed rail loses a significant portion of its heat output straight out the duct. The electrician and tiler need to sort this out at rough-in stage. Combination heat and exhaust units are worth considering in smaller bathrooms. Confirm the heat element wattage alongside the fan’s airflow rating — both numbers matter.
Ventilation Is the Part of the Cold Bathroom Problem That Most Renovations Miss
The most common cause of a bathroom that stays cold and damp through winter isn’t a missing heater. It’s an exhaust system that isn’t working — underpowered, incorrectly ducted, or simply failed at some point and never replaced. Adding heating to a bathroom with inadequate ventilation reduces the symptom without fixing the cause.
Here’s what happens: warm shower steam hits cold tile surfaces, condenses, and sits there. Wet surfaces draw heat out of the air. The bathroom stays cold and damp even when the heating is on. Adequate exhaust pulls the humid air out before it condenses. Tiles dry faster, ambient temperature holds, and the heating you’ve specified can actually do its job. These are not separate problems that can be solved independently.
AS 1668.2 specifies a minimum exhaust rate of 25 L/s for a bathroom, ducted to outside — not recirculated, not vented into the ceiling cavity. That second point matters. In older homes and some renovated bathrooms, exhaust fans are frequently found ducted into the roof space rather than terminated at an external vent. The fan runs. It sounds like it’s working. Humid air dumps into the ceiling cavity, condenses on timber and insulation, and the bathroom stays damp regardless of what’s been spent on heating.
When sizing a replacement exhaust fan, look at the airflow specification — listed in L/s or m³/hr. For a standard bathroom: 25–35 L/s (90–125 m³/hr). For a bathroom with a separate shower enclosure and a freestanding bath, go higher. Products often lead with sone ratings (noise level) in the marketing and bury the airflow number in the specs. Check the airflow figure, not how quiet the unit is supposed to be.
Heat recovery ventilation (HRV) is worth knowing about for bathrooms in colder parts of the country — ACT, the upper elevations of NSW, anywhere with consistent winter temperatures below five degrees. An HRV unit recovers heat from outgoing exhaust air before it leaves the building and uses it to pre-warm incoming air. Supply and installation for a bathroom-scale unit runs $600–$1,300. It’s not the right specification for every project, but in a heavily used bathroom in a cold climate, it pays back over a few winters.
Related: NCC bathroom standards govern minimum ventilation requirements for wet areas. See our NCC bathroom standards guide ›
Heating and Ventilation Failures That Show Up After the Job Is Done
The common thread in heating failures — like tiling failures — is that the conditions that caused them were present from day one. They just didn’t surface until weeks or months later, usually after the trades have moved on.
Wrong adhesive specified under the heating mat
A mat installed under tiles bedded with standard adhesive where flexible was required will eventually fail. The mat creates a thermal expansion and contraction cycle every time it runs — small movements, but consistent ones. Standard adhesive accommodates less movement than flexible. The bond breaks over time. Tiles go hollow, then crack or lift. The mat itself is usually fine. The reinstallation isn’t cheap, and it involves pulling up tiles that were otherwise fine. Confirm adhesive compatibility with the mat manufacturer in writing before the tiler orders supplies.
Exhaust fan ducted to the ceiling cavity, not outside
More common than it should be, particularly in older homes and some renovated bathrooms where the exhaust job was done quickly. The fan runs. It sounds like it’s working. The duct terminates in the roof space rather than at an external vent. Warm humid air dumps into the ceiling cavity where it condenses on timber and insulation. The bathroom stays damp and cold regardless of what’s been specified for heating. Check where the exhaust duct actually terminates before signing off on any heating scope. It’s a five-minute check with a torch that can change the entire specification.
Treating a heated towel rail as the primary heat source
A 200W towel rail in a 14m² bathroom with an external wall and no underfloor heating is not going to produce a warm bathroom in a Canberra winter. It will produce warm towels. If the renovation brief said ‘warm bathroom in winter’ and the delivered solution was a hardwired rail, the specification didn’t meet the brief. This gap tends to happen when heating isn’t specifically discussed during the renovation consultation — everyone assumes someone else has covered it, and no one has. Put the heating question on the agenda early.
Underfloor mat positioned across a movement joint
Movement joints exist because buildings move. Fractionally, seasonally, but they move. An electric mat laid across a movement joint or expansion joint will flex with that movement. That stresses the cable. The failure mode is usually not immediate — it develops over weeks or months. By the time it shows up the tiles are grouted, possibly sealed, and removing them to replace the mat is a significant job. The mat layout needs to be confirmed against the tile layout and the movement joint positions before either the mat or the tiles go down. It’s a pre-installation conversation, not a site decision.
Important: Substrate, adhesive, and exhaust work is where the most meaningful shortcuts get taken when a contractor is under price pressure. A quote that doesn’t itemise electrical work and substrate preparation separately should prompt questions rather than satisfaction. See renovator red flags ›
What Bathroom Heating Costs in NSW and ACT
The ranges below are indicative, not quotes. Substrate condition, existing electrical board capacity, and whether the bathroom is mid-renovation or finished all move these numbers in either direction. Labour varies with access and how honestly the scope has been written.
The ranges below are not quotes. Scope and site conditions move these numbers significantly in either direction.
A quote that doesn’t itemise electrical work separately from the product supply is worth querying before you sign. That’s where most of the cost variation sits, and where the most meaningful shortcuts get taken when a contractor is under price pressure.
Related: For a full picture of how heating costs sit within a bathroom renovation budget. See our bathroom renovation cost guide ›
Have a question about how to specify heating for your bathroom? We connect homeowners with experienced, vetted renovation specialists across NSW and ACT. Lifestyle Bathrooms is a referral and connector service — not a licenced contractor. Request a free consultation ›
Before You Specify Bathroom Heating
Nine things to confirm before engaging a specialist or ordering products. Most of the failures covered in this guide trace back to one of these not being addressed early enough.
Exhaust compliance confirmed
Confirm airflow meets AS 1668.2 minimum (25 L/s) and is ducted to an external vent — not the ceiling cavity. Fix this before specifying heating. They’re not independent problems.
Heating intent defined — primary vs supplementary
Is the spec intended to make the bathroom comfortable in winter, or to supplement an already-warm space? These need different solutions and different wattages. Clarify this in the brief before anyone quotes.
Substrate assessed for mat compatibility
Confirm the tile substrate is dimensionally stable, flat to required tolerance, and that movement joint positions are correctly located before the mat layout is drawn up.
Adhesive type confirmed with mat manufacturer
Don’t assume standard adhesive is compatible. Get written confirmation from the mat supplier that the adhesive your tiler is specifying is on their approved list.
Electrical board capacity checked
Additional circuits for underfloor heating and hardwired towel rails require board capacity. If an upgrade is needed, that cost belongs in the quote from the start — not as a site discovery.
Licensed electrician confirmed for all electrical work
Hardwired heating installations require a licensed electrician (Class 1 licence, NSW). Confirm the licence before engagement. This applies to towel rails and heating mats.
Mat layout confirmed against movement joints
The mat must not cross movement joints or expansion joints. Confirm the layout against both the tile plan and the joint positions before installation. Not a day-of decision.
Thermostat sensor position agreed before tiling
The floor sensor position needs to be set before tiles go down. Moving it afterwards means breaking tiles. Agree the position with the installer at the planning stage.
Heating and exhaust placement coordinated
Heated towel rail position relative to exhaust fan path needs to be resolved at rough-in. Trades need to coordinate on this before fitting, not after.
Common Questions
Not without lifting them. The heating mat sits between the substrate and the tile adhesive bed — you can’t retrofit it under laid tiles without removing the tiled surface first. In a bathroom that’s mid-renovation with tiles already up, it’s straightforward to include as part of the retile. In a finished bathroom where no other work is planned, the cost of retiling needs to go into the calculation, which usually changes the conversation.
One practical detail worth sorting at the design stage: a mat adds approximately 3–4mm to floor height. That affects door clearance and any floor-level transition strips between rooms. Small enough to manage with planning, awkward to fix once tiles are down.
In most cases, yes — and the mat manufacturer’s warranty generally requires it. A dedicated circuit (not shared with other bathroom fittings) is standard practice and eliminates the risk of nuisance tripping from a shared load. Whether the switchboard has capacity for an additional circuit is a question for a licensed electrician at rough-in stage, not an assumption. If an upgrade is needed, that cost belongs in the quote from the beginning.
A combination exhaust/heat unit handles ventilation compliance and supplementary heat in a single fitting — practical for a small bathroom where one fitting does both jobs without consuming additional ceiling real estate. If the floor is being retiled as part of the renovation, a small electric mat covering the shower exit zone and main standing area adds meaningful warmth for relatively modest cost. Those two together cover most use cases in a small bathroom without overcapitalising on the heating specification.
Yes, and it works well. Large tiles distribute heat evenly across their surface area and the thermal mass means they hold warmth longer once they’ve reached temperature. The installation requirements are stricter — flexible adhesive is mandatory for large-format in any case, back-buttering is required under AS 3958, and the mat must not cross movement joints. None of that is specific to underfloor heating; it applies to any large-format tile installation. The heating layer adds one coordination step: confirm adhesive compatibility with the mat manufacturer before the tiler places the order.
For most bathrooms in NSW and ACT, no. A standard residential towel rail at 150–300W contributes meaningfully in a very small space — a compact ensuite or powder room under 6m². In a full bathroom with an external wall, a shower and a bath, the output isn’t there. If the answer to the question ‘how are we heating this bathroom’ is a towel rail and nothing else, either the scope of the problem hasn’t been understood or the options haven’t been properly laid out. Towel rails are supplementary. They need something to supplement.
Getting the Heating Specification Right Before Work Starts
The decisions made before your trades arrive — ventilation compliance, heating type, electrical capacity, adhesive specification — are the ones that determine whether the bathroom is actually warmer after the renovation. Getting them right is substantially cheaper than fixing them later.
Lifestyle Bathrooms is a referral and connector service, not a licenced contractor. We connect homeowners, investors, and property professionals in NSW and ACT with vetted bathroom renovation specialists.