Nordic Wooden Spa: How It Works, Ideal Temperature, and How to Choose the Right

How Does a Nordic Wooden Spa Work?

A Nordic wooden spa, also known as a Scandinavian spa or Nordic hot tub, is an outdoor bath designed for relaxation. It consists of a wooden tub filled with heated water, where you immerse yourself to enjoy a moment of relaxation outdoors.

The main difference between models lies in how the water is heated, as each system has its own specific features.

Wood-Fired Nordic Spa

This is the most traditional format. A wood stove is either immersed directly in the tub or positioned outside and connected via pipes, fueled by logs. The water heats up through natural circulation (thermal convection), without an electric pump. This system, called a thermosiphon, does not require any electrical connection: hot water rises and cold water descends, creating automatic circulation.

However, you need to plan for heating time in advance, generally 1.5 to 3 hours depending on the size of the tub, the outside temperature, and the quality of the wood.

Electric Nordic Spa

An electric heater (usually 3 kW) keeps the water at a constant temperature, coupled with a filtration pump and hydro-massage jets. The spa is available at any time, without prior preparation. This is the most practical option for daily or semi-daily use.

Hybrid Nordic Spa

Some models combine both systems: a wood stove for a traditional experience and rapid heating, plus an electric heater to maintain the temperature between uses. This is often the best compromise between authenticity and comfort.

How Does the Jet System Work?

In models with hydro-massage, a pump circulates water through nozzles integrated into the tub. The jets are adjustable in power and direction, targeting specific areas of the body. Depending on the model, you can find 12 to 16 jets, interior LED lighting, and control via keypad or smartphone. Purely wood-fired models do not have jets, as relaxation comes from the heat of the water rather than massage.

What Is the Ideal Temperature for a Wooden Spa?

This is one of the most frequently asked questions, and the answer is quite simple.

The ideal temperature for a wooden spa is between 37°C and 40°C. This range allows you to relax your muscles, improve blood circulation, and fully enjoy the immersion without the risk of overheating for a healthy adult.

Beyond 40°C, prolonged immersion becomes uncomfortable and is not recommended, especially for vulnerable individuals.

In an electric or hybrid model, the temperature is automatically managed by a thermostat. In a wood-fired model, you control it by adjusting the intensity of the fire and, if necessary, adding a little cold water.

How Long Does a Session Last?

Most users stay between 15 and 30 minutes per session. Beyond that, the heat can become overwhelming. If you practice hot/cold alternation, a session consists of cycles of 10 to 20 minutes in the hot water, followed by 1 to 3 minutes in cold water or fresh air, repeated 2 to 3 times.

How to Choose an Outdoor Wooden Spa: 6 Key Criteria

1. Heating Method

This is the first decision to make. Ask yourself about your actual usage:

If you enjoy the ritual and spontaneity is not your priority, and you have space to store wood: the wood stove is the most authentic option.

If you want the spa to be available at all times, without preparation: the electric model is the way to go. The heating is automated, but you need to consider the electrical consumption in your operating budget.

If you want both: the hybrid model is often a good option, especially for families.

2. Size and Capacity

Wooden spas range from 2-person models (150 cm in diameter) to 10-person models (240 cm). For a family of 4 to 5 people, the 180 cm diameter is generally the right balance. For regular use among adults, a 150 cm model may suffice.

Beyond capacity, consider the total weight: a filled tub with its users can weigh over a ton. You need a stable surface (concrete slab or reinforced terrace) to accommodate it safely.

3. Type of Installation

Three formats are available on the market:

Above-ground spa is placed directly on a terrace or slab. It is the simplest and most flexible option—it does not require any construction work and can be moved if you reorganize your outdoor space. The exterior wood cladding can be integrated or added.

Built-in spa integrates into the floor of your terrace. The result is an almost invisible, very elegant look that preserves the visual continuity of the space. The machinery is hidden under the floor.

Semi-built-in spa is a compromise: the tub is partially recessed, with visible cladding above the floor. It requires less work than a fully built-in spa but offers more integration than a purely above-ground model.

4. Wood: Solid or Cladding?

This is a point often poorly explained in product descriptions. Two realities coexist under the term "wooden spa":

A wood-clad spa has a tub made of acrylic or composite, with wooden slats placed on the outside for aesthetics. This is the most common configuration in mass distribution.

A solid wood spa has a tub whose entire structure is made of wood, with thick staves (often 38 mm) in direct contact with the water. The wood provides thermal insulation, releases its natural aromas, and constitutes the structure itself.

Durability, insulation, and sensory experience are significantly superior in the latter case. Among the most commonly used woods: Red Cedar (naturally rot-resistant, highly aromatic), larch (robust, European), and thermally treated wood (heat treatment without chemicals).

At Storvatt, we work exclusively with Clear 2 Red Cedar for our entire range of outdoor wooden spas, manufactured in the French Alps since 1997.

5. Origin and Manufacturing

The question of French or European manufacturing is increasingly relevant, and rightly so. It has concrete implications: quality of the wood used, manufacturing control, availability of after-sales service, and delivery times for spare parts.

A spa manufactured in France or in a country with a tradition of woodworking (Scandinavian countries, Baltic countries) will generally offer better long-term guarantees than an imported model without traceability. Check the origin of the wood and the availability of customer service.

6. Equipment and Options

Beyond the choice of the basic model, several options can make a real difference:

The thermal cover is essential: it limits heat loss between sessions and significantly reduces electricity consumption or the need for wood.

The filtration system (cartridge or sand) determines the frequency of draining and water quality. With effective filtration, water can last 2 to 3 months before needing to be changed.

LED lighting with color changes is often included in models with hydro-massage, transforming the comfort of use in the evening.

Remote control via smartphone, available on some models, allows you to start heating before you arrive home.

What Budget Should You Plan for a Wooden Spa?

The price of a wooden spa varies considerably depending on the criteria mentioned above. Here is a realistic price range for the French market in 2025-2026:

These prices do not include installation. Plan for an additional budget for ground preparation, electrical connection (which must be done by a qualified electrician, with a 30 mA differential circuit breaker), and delivery, which can vary depending on the accessibility of the location.

The annual operating budget (maintenance products, filtration, energy) is generally between €200 and €500 for regular use in an electric model, and significantly less for a wood-fired model.

Wooden Spa Maintenance in Practice

Maintaining a well-designed wooden spa is less demanding than often imagined.

Every week, check the pH of the water (ideally between 7.2 and 7.6), add bromine or chlorine tablets according to the chosen treatment, and rinse the filter cartridge.

Every 2 to 3 months, for regular private use, drain the tub, rinse the inside (a sponge is sufficient for a solid wood tub), and refill.

For wood-fired models, remember to empty the ash drawer before each use and only use dry wood (moisture content less than 20%) for quick heating without excessive smoke.

The exterior wood (tub and cladding) does not require any treatment for naturally rot-resistant woods like Red Cedar. It will gradually weather to a silvery-gray hue without losing its properties. If you wish to preserve the initial golden hue, a protective oil can be applied once or twice a year on the outer surface only. Never inside, to avoid blocking the natural exchanges between the wood and the water.

Frequently Asked Questions

Do you need a building permit?

Generally, no. A spa placed on a terrace or on the ground does not require a building permit. Specific rules may apply if you build a shelter around it or depending on your local urban planning regulations.

Is a rigid wooden spa more durable than an inflatable model?

Yes, without comparison. An inflatable spa is temporary equipment, poorly insulated, with a lifespan of 3 to 5 years under the best conditions. A well-maintained rigid wooden spa can last several decades.

What is the difference between a wooden spa and a Nordic bath?

The wooden spa with hydro-massage is equipped with massaging jets and electric filtration. The water is always available at temperature, without preparation. The traditional Nordic bath is heated by a wood fire, without jets, with a preparation ritual that is part of the experience. Both can be made of solid Red Cedar and can be used outdoors all year round. The choice depends on what you are looking for: immediate comfort or a sensory experience.