A sauna that gets used four times a week by one family is a very different machine than one that runs twelve hours a day in a gym. Commercial sauna design has to account for near-constant heat cycling, a stream of people who don't know how to use the room, and an inspector who wants to see everything on paper before you open. Most of the problems we see in commercial saunas come from someone designing them like an oversized home sauna. That's where it goes wrong.

If you're putting a sauna in a gym, hotel, wellness studio, or a short-term rental you run at scale, the fundamentals don't change — heat, steam, ventilation, and bench geometry still decide whether the room is good. What changes is the load. Everything gets used harder, sits under more scrutiny, and costs more to get wrong. Here's what actually matters.

Commercial vs. Residential: What's Actually Different

The physics of a good sauna are the same whether it's in your backyard or a hotel spa. The difference is duty cycle and liability.

A home sauna heats up, gets used for an hour or two, and cools down. A commercial sauna may run continuously from open to close, cycling through dozens of bathers. That constant use means everything wears faster — the heater, the benches, the door hardware, the wood. It also means the room almost never gets a chance to fully dry out between sessions, which makes ventilation and material choices far more important than they'd be at home.

Then there's code. A residential sauna in most places needs an electrical permit and maybe a building permit. A commercial installation is a different world: occupancy ratings, ADA access, tempered safety glass, GFCI protection, emergency egress, and often a fire inspection. The heater almost always needs to be UL listed, and the authority having jurisdiction (AHJ) will check. You can't wing any of this. If you're weighing whether to bring in a designer at all, our take on what a sauna designer actually does applies double for commercial work — the cost of a mistake is much higher.

Sizing the Heater for Continuous Use

Heater sizing for commercial saunas follows the same baseline rule as residential — roughly 1 kW per 45 cubic feet of a well-insulated, wood-lined room — but the numbers get big fast and the details change.

A commercial room running 1,000+ cubic feet lands in the 15 to 72 kW range. At that scale you're usually looking at:

• Large three-phase electric heaters — most commercial units run on 208V or 240V three-phase power, not the single-phase 240V a home heater uses.
• Gas heaters — for very large rooms (600+ cubic feet) or facilities already plumbed for gas, a gas heater heats fast and holds temperature consistently under heavy load. Scandia is one of the few brands offering gas units.

One commercial-specific trap: 208V wiring. A lot of commercial buildings run 208V three-phase power instead of 240V. You can wire a 240V single-phase heater to a 208V system using two hot legs, but it drops the heater's output by about 25%. If you size the heater assuming 240V and then run it on 208V, you end up with a room that never quite gets hot. Size up to account for it, and confirm the actual supply voltage with your electrician before ordering anything. The same principles from our sauna heater sizing guide apply — you just have to layer the voltage and duty-cycle adjustments on top.

Because commercial rooms run constantly, oversizing slightly is usually the right call. It buys faster recovery between the door opening and closing all day, and it compensates for the heat loss you get from glass walls and high-traffic doors.

Ventilation Is Non-Negotiable at Commercial Scale

In a home sauna, bad ventilation gives you a stale room and cold feet. In a commercial sauna with people cycling through all day, it becomes a genuine air-quality problem.

When several people sit in a sealed room for 20+ minutes, they exhale CO₂ and consume oxygen. Without real ventilation, CO₂ climbs — we've measured unventilated rooms peaking around 1,200 ppm, well past the point where people feel dizzy, foggy, or short of breath. The target is below 700 ppm during use, and a properly ventilated room holds that. In a commercial setting where you're responsible for public safety, that's not a nice-to-have.

The design that actually works for electric saunas is mechanical downdraft ventilation: fresh air supplied high on the wall above the heater, and a powered exhaust pulling stale air out from below the foot bench on the opposite wall. Plan for roughly 20 to 25 CFM per person plus another 15 to 25 CFM to cool the heater's high-limit sensor. For a room rated for eight people, that's meaningful airflow, and it needs a real inline blower, not a passive vent. Our full sauna ventilation guide walks through the placement in detail — the commercial version is the same logic, just sized up and, ideally, on a system that can also run a post-close drying cycle to keep mold out of a room that never rests.

Materials and Benches Built for Abuse

Commercial saunas take a beating, so the material and layout decisions lean toward durability and cleanability.

Wood: Western red cedar is the standard for commercial interiors because its natural moisture and decay resistance is a real advantage in a room that stays damp. It costs more than hemlock or aspen, but in a space that never fully dries out and gets cleaned constantly, it earns it.

Benches: Use an open, minimalist bench design — 2x4 slats on wall-mounted cleats with visible, accessible floor underneath. Do not enclose the fronts of the benches. In a commercial room, sweat drips through the bench slats to the floor all day. If the space under the benches is sealed off, you can't clean it, and moisture accumulates in an inaccessible cavity. That's a hygiene failure waiting to happen. Keep the floor under the benches open and cleanable.

Foot bench hygiene: This matters more commercially than anywhere. The foot bench needs to reach 55 to 70°C (131 to 158°F) to kill bacteria and mold — ideally 65°C for 20 minutes. That's a function of ceiling height, bench positioning, and ventilation working together. A room where the foot bench stays cold isn't just uncomfortable; in a shared public space it's a sanitation problem.

Floor and drainage: Tile or sealed concrete with a floor drain and a slight slope (about 1/4 inch per foot toward the drain) makes daily cleaning practical. A drain isn't strictly required at home, but for a commercial room getting mopped every day, it's worth it.

Code, ADA, and Permits

This is where commercial work separates from residential, and where cutting corners gets expensive.

Expect to deal with occupancy limits, ADA-accessible design (door width, turning radius, bench transfer space), tempered safety glass on any door or window, GFCI protection on all circuits, high-temperature IP-rated light fixtures, and emergency egress — the door always opens outward, never locks, and uses a simple latch. Most commercial installs also need the heater to be UL listed and the whole thing signed off by an electrician and, often, a fire inspection.

The realistic move is to loop in your AHJ early, before the design is final. Requirements vary a lot by jurisdiction, and it's far cheaper to design around them than to retrofit after a failed inspection. If you're also handling the structure, our notes on sauna permit requirements cover the residential baseline — commercial adds layers on top of it, but the same documentation discipline applies.

The Rental and Hospitality Angle

Not every commercial sauna is a gym locker room. A growing share of what we see is hospitality — hotels, lodges, wellness studios, and short-term rental operators adding a sauna as an amenity that drives bookings.

The design priorities shift a little here. Durability and low maintenance still lead, but guest experience and the look of the room carry more weight. A hotel sauna that photographs well and delivers a genuinely good session is a marketing asset. One that's cramped, weak, or poorly ventilated generates complaints. If you run a rental property, the same logic that makes a sauna worth it for a short-term rental or Airbnb scales up — the amenity only pays off if the room is actually good, and at commercial volume the design has to hold up to constant turnover.

For operators running semi-permanent or mobile commercial saunas — think a lodge hosting a unit for guests — a gas-fired setup with booking software and a clear maintenance plan can pencil out to a solid return, but only if the unit is sized and ventilated for the traffic it'll actually see.

Frequently Asked Questions

How much does a commercial sauna cost?

It varies widely with size, heater type, and finish level, but commercial installations typically start well above residential — often $15,000 to $50,000+ once you account for a large three-phase or gas heater, code-compliant construction, ADA access, and commercial-grade materials. The heater alone at commercial scale (15 to 72 kW) is a significant line item. Get the design and code review done first so you're pricing a real scope, not a guess.

What size heater does a commercial sauna need?

Follow the baseline of roughly 1 kW per 45 cubic feet, then adjust up for glass, high-traffic doors, and continuous use. Commercial rooms over 1,000 cubic feet generally need 15 kW and up, running on three-phase power. If your building is 208V rather than 240V, size up by about 25% to account for the power drop.

Do commercial saunas need special ventilation?

Yes. With people cycling through all day, CO₂ management is a real health concern. A mechanical downdraft system — fresh air above the heater, powered exhaust below the foot bench — is the only design that reliably keeps CO₂ under 700 ppm and dries the room between uses. Passive vents don't cut it at commercial volume.

Can I use a residential sauna heater in a commercial space?

Usually not. Commercial installations almost always require a UL-listed heater sized for continuous duty and often three-phase power, and your inspector will check. Residential single-phase units aren't built for the load or the code requirements of a public space.

What are the ADA requirements for a commercial sauna?

Commonly a wider door for wheelchair access, adequate turning and transfer space inside, a bench arrangement that allows transfer, and accessible controls. Exact requirements depend on your jurisdiction and occupancy type, so confirm with your AHJ during design rather than after.

Getting It Right the First Time

Commercial sauna design rewards planning and punishes shortcuts. The rooms that work are the ones where heater sizing, ventilation, materials, and code all got sorted on paper before anyone cut a board — not after an inspector or a stream of unhappy guests forced a redo.

If you're planning a commercial sauna for a gym, hotel, studio, or rental operation, that's exactly the kind of project our remote sauna design service is built for. We can work through sizing, ventilation, code, and layout with you and your contractor no matter where you're located, and hand your builder a plan set they can actually execute. Start with our sauna design checklist to get your requirements straight, then let's talk through the specifics.