Most sauna problems in hotels are specification problems, not product problems. The cabin arrives, it is a good cabin, and it is the wrong cabin for a room that runs sixteen hours a day with a housekeeping team, a BMS, a fire strategy and a guest who will complain in writing.

This is the guide we would want an MEP consultant or a project manager to have before writing the spa package. It is deliberately technical, and it applies whoever supplies the room.

1. Duty rating comes before everything else

A domestic sauna is used for an hour, three times a week. A hotel sauna is at temperature from 06:00 to 22:00, every day, for years.

That difference lands on three components: the heating elements, the contactor that switches them, and the temperature sensor. Domestic-rated versions of all three exist inside heaters that otherwise look identical to commercial units, and they are the reason a hotel sauna that was “the same model my client has at home” fails inside two years.

Specify the duty rating explicitly. Ask for the manufacturer’s stated continuous-operation hours and the element warranty under commercial use, in writing. If a supplier cannot produce it, that is your answer.

2. Heater sizing: the arithmetic, and the correction nobody applies

The base rule is approximately 1 kW per cubic metre of cabin volume for a fully insulated timber room.

The correction is where specifications go wrong. Add roughly:

• +1.2 kW per square metre of glass. A full glass front on a 9 m³ cabin can add 3 to 4 kW on its own.
• +1 kW per square metre of uninsulated masonry or stone in contact with the cabin.
• +15% if the cabin sits against an external wall in an unconditioned space.

A 9 m³ cabin with a glass door needs about 9 kW. The same cabin with a full glass front needs 12 to 15 kW. Specifying 9 kW for both — which happens constantly — produces a room that never reaches setpoint, an element running permanently at full output, and a warranty claim in year two.

Size against the room as drawn, never against the heater catalogue’s maximum cabin volume. Catalogue figures assume the ideal insulated box.

3. Ventilation

The single most under-specified item, and the one that determines whether the room is pleasant.

A commercial sauna needs mechanical or well-designed passive ventilation providing roughly 6 to 8 air changes per hour, arranged as:

• Supply low, near or beneath the heater, so incoming air is drawn across the element.
• Extract high on the diagonally opposite wall, or low on that wall with a duct rising outside the cabin.
• No short-circuiting. Supply and extract on the same wall produces a dead zone at the far end.

Get the air path onto the drawings. A gap under the door is not a ventilation strategy, and in a hotel it usually means the corridor gets the smell of the cabin.

4. Electrical

• Dedicated circuit, correctly rated, with an isolator outside the cabin in an accessible position.
• Heaters above roughly 9 kW are three-phase; confirm the available supply early, because upgrading it after the spa is built is expensive.
• All in-cabin fittings IP54 minimum; IP65 in steam rooms and in any position where water is used.
• Luminaires must be rated for the cabin temperature, and their drivers must sit outside the hot zone.
• Provide a volt-free contact for the BMS if the client wants remote enable, scheduling or alarm reporting. Retrofitting it is disproportionately painful.

5. Timber

Species is a performance decision, not only an aesthetic one.

• Nordic spruce — the default. Ask for the grade; clear, knot-free grades behave better and look better after five years.
• Abachi / ayous — low thermal conductivity, so it stays comfortable to touch at temperature. The standard choice for benches and backrests.
• Thermally modified timber — dimensionally more stable in high humidity, darker, more expensive.
• Cedar — aromatic, stable, but the scent is not universally welcome in a hotel and it is a cost step.

Whatever the species, benches and any surface a guest touches should be in a low-conductivity timber, fixed with concealed fixings. Exposed metal at 90 °C is a burn.

6. Fire and compliance

For hotel work in the Gulf you should expect to provide:

• CE marking on heater and control system, with a declaration of conformity.
• Fire performance data for the wall and ceiling linings, to the standard the authority or the fire consultant nominates.
• Material approval submissions, typically with datasheets, test certificates and samples.
• Coordination with the building’s detection and suppression strategy — a heat detector inside a sauna needs a setpoint that makes sense, and this is a conversation the fire consultant needs early.
• An overheat cut-out on the heater, which is standard but should be stated.

We produce this as a combined submittal package. If your supplier has never assembled one, that is a programme risk rather than a quality signal.

7. Hygiene, maintenance and the operator’s reality

Specify for the housekeeping team, not the photograph.

• Removable bench sections so the floor beneath can be cleaned. Fixed benches over a tiled floor guarantee a smell within a year.
• Floor gully with an accessible trap where the cabin is washed down.
• Access to the heater for element replacement without dismantling joinery.
• A published maintenance schedule — stone re-stacking, element inspection, sensor calibration, door seal check.
• Stones should be replaced periodically; they degrade, and degraded stones restrict airflow through the heater and shorten element life.

8. Capacity and throughput

An often-missed commercial calculation. Allocate roughly 0.6 to 0.8 m² of bench per person for realistic comfort, not the theoretical maximum.

Then decide what the room is for. A traditional high-temperature cabin turns over guests in eight to twelve minutes. A recovery-focused room at moderate temperature holds them for twenty-five to thirty. That is a three-fold difference in required seats for the same number of guests per day, and it should drive the room size before the interior designer starts.

9. What to put in the tender document

At minimum:

1. Internal dimensions and finished ceiling height of each room.
2. Required heater output in kW, with your glass and stone corrections shown.
3. Duty rating: continuous commercial operation, hours per day.
4. Control system: location, BMS interface, scheduling requirement.
5. Ventilation rate and the supply/extract arrangement.
6. Timber species and grade, separately for linings and benches.
7. Glass specification: toughened, thickness, edge treatment.
8. IP ratings for all in-cabin electrical items.
9. Certification and submittal deliverables.
10. Scope split for builder’s work, waterproofing, drainage and electrical supply.
11. Installation scope, including whether travel and accommodation for the installation team are included.
12. Warranty terms, split between appliance, cabin and labour.
13. Spare parts to be handed over at practical completion.

A tender that specifies items 1 to 13 will get comparable prices back. One that says “supply and install sauna, approx. 3 × 3 m” will get a spread of four hundred per cent and no way to judge it.

10. The commercial questions behind the technical ones

Who owns the interfaces? Waterproofing, floor falls, drainage, electrical supply, the junction with adjoining finishes. Most disputes on spa packages sit here, not in the cabin.

What is the real lead time, by stage? Design and approvals, manufacture, shipping, installation, commissioning. Shipping to the Gulf and Africa is where programmes slip.

Who is on site for commissioning, and what is the handover document? A room that has been switched on is not a room that has been commissioned.

We manufacture and install commercial spa packages — saunas, steam rooms and hammams — for hotels and developers, and we will happily be measured against this checklist. If you want the appliance-level view first, our comparison of the major sauna brands sets out who makes what, and our buyer’s checklist covers supplier selection. For budgeting, we publish real AED ranges.

Frequently asked questions

What kW sauna heater does a hotel sauna need?

About 1 kW per cubic metre of cabin volume, plus roughly 1.2 kW per square metre of glass and 1 kW per square metre of uninsulated stone. A 9 m³ cabin with a glass door needs around 9 kW; the same cabin with a full glass front needs 12 to 15 kW.

How much ventilation does a commercial sauna need?

Roughly 6 to 8 air changes per hour, with supply low near the heater and extract high on the opposite wall. Supply and extract on the same wall creates a dead zone.

What IP rating is required inside a sauna?

IP54 as a minimum for fittings inside a dry sauna; IP65 in steam rooms and any washed-down area. Luminaire drivers should sit outside the hot zone.

What certification does a commercial sauna need in the UAE?

CE marking with declaration of conformity for heater and controls, fire performance data for linings, and a material approval submittal package for the authority and the fire consultant.

How many people fit in a commercial sauna?

Allow 0.6 to 0.8 m² of bench per person for real comfort. Size the room from the intended dwell time: a hot traditional cabin turns over in eight to twelve minutes, a moderate recovery room in twenty-five to thirty.

Can a sauna be connected to a building management system?

Yes, via a volt-free contact on the control unit for remote enable, scheduling and alarm reporting. Specify it at tender; retrofitting it is disproportionately expensive.