If you’re unfamiliar with the term ‘heat density,’ it’s worth taking a moment to understand why it’s a crucial factor in a sauna’s performance and, most importantly, how it impacts the body.
Heat density is a metric sauna engineers use to determine the heat felt inside the cabin. For science buffs, it is the total wattage inside the sauna cabin divided by the amount of space and is usually expressed as watts per cubic meter (W/m³). Think of it as a way to measure heat quality.
In practical terms, a sauna’s heat density score indicates how quickly the cabin reaches the target temperature, how effectively the heat transfers to the body, and the overall intensity of the sauna experience. A higher heat density means your body receives more infrared light in a shorter period, which hastens the onset of hormesis—the beneficial stress associated with sauna. The benefit to the user is efficiency. You can spend more time within the health benefit zone but less time in the sauna overall.
In the broadest terms, the measurable physiological effects of sauna are:
To do this, we must increase our core body temperature by 0.8 – 1.2+ degrees. There are two ways to achieve this using sauna.
Traditional Sauna Method—In a traditional sauna, the cabin is pre-heated to 50 – 90 degrees. You feel the intense heat envelop you as you enter, and slowly, the room’s heat transfers to the body, raising the core temperature. However, there is a time lag between first exposure and achieving the hormetic response. That’s because the body’s initial response is to counter the heat by dropping heart and breath rates.
Thermo-Neutral— A sauna session in a thermo-neutral cabin can start at room temperature. With your back towards the heaters, the blood around your spine heats quickly and circulates the body. As the body and the room heat up simultaneously, there is no resistance response, and lifting the core body temperature and triggering the hormetic response happens faster.
The ideal is to have both options available—a sauna that you can preheat to feel that initial wave of warmth as you enter, but also have the option of starting from ambient temperature. And that’s precisely what you have with a Found—Space infrared sauna: hormetic technology bridging the gap between traditional and infrared.
Three main factors will determine the heat density of a sauna.
1: The total wattage.
How much electricity does the heater need to heat a defined space? This is where the actual Heat Density W/m³ measurement comes in handy. Any decent quality sauna will measure over 700 W/m³.
At Found—Space, we’ve partnered with industry leaders Sentiotec of Austria to fit the Nu-a saunas with some of the world’s best and most potent heaters, achieving a minimum heat density of 850 W/m³.
2: The reflective yield of heaters
One factor that makes Sentiotech heaters more effective is their engineering, which allows them to reflect more of the full spectrum infrared light energy toward the user. This is done by using a special type of stainless steel in the reflector, which can achieve a high polish to maximise the amount of light that is reflected and not absorbed.
Additionally, the shape of the Sentiotec reflector generates an even ray of full-spectrum light at 122 degrees outwards from the heater, which research shows is the ideal configuration. Unlike generic infrared heaters, the Sentiotec heaters have no areas with a stronger or weaker reflection.
The Sentiotec heater emits 3x the amount of light than generic infrared heating panels.
This light spectrum analysis report shows the amount of light, measured in Watts, emitted from the Sentiotec full-spectrum heater used in the Found—Space Nu-a (right) compared with a generic full-spectrum heater (left).
3: The proximity and number of heaters
The spatial arrangement within the sauna cabin is just as critical as the heaters themselves. The user’s proximity to the heat source significantly influences the sauna experience and the sensation of heat. Found—Space sauna designs are strategically planned to ensure that the user is always within an optimal distance from the heaters, maximizing the absorption of infrared light. This careful consideration of space and positioning means that the beneficial effects of the sauna are both intensified and accelerated, leading to more effective sessions.
Below is a graphic published by a company that manufactures red light therapy devices. As you can see, the further you are from the heater, the less light you receive.
To receive the most benefit from the infrared heaters, they should surround you and be as close as possible to your body.
Many infrared sauna companies claim their products are ‘full spectrum’; however, only one or two of the heaters will actually be full spectrum, and they are usually positioned too far inside the front wall to provide any proper therapeutic benefit.
The Nu-a collection has at least 2x the number of full-spectrum heaters than any equivalent model and comparable size on the market.
Below is an image demonstrating the difference in the amount of light received in a Found—Space Nu-a III compared with the equivalent from another company.
Other Brand
Found—Space Nu-a III
Nu-a’s design ensures that you’re not just sitting in a warm room but are enveloped in more red light and full-spectrum infrared light than any other sauna.
Understanding heat density, heater performance and cabin design is essential when comparing infrared saunas and should guide your decision-making.
When comparing infrared saunas, it is important to remember that the quality of the heaters is a significant component of the cost of a sauna. Many sauna companies compromise using inferior heaters because it makes the unit cheaper, and customers rarely need special wiring to supply power. However, the payoff is reduced heat density. The sauna takes longer to heat up, so the time it takes to reach and stay within the critical health benefit zone is diminished. It’s a false economy.
Every Found—Space sauna is a testament to our dedication to quality and effectiveness. We’re not just selling saunas; we’re offering a gateway to a healthier, more vibrant life. Our range of premium, luxurious, hormetic technology ensures that you receive the maximum benefits with every session, making every moment in a Found—Space sauna a step towards optimal health.
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