Infrared Sauna Buyer's Guide: What Really Matters

The process of researching and buying an infrared sauna can be frustrating. It's a highly-competitive field where marketing jargon and misleading information are used to confuse consumers. It doesn't help that online sources of information are often tainted by financial conflicts of interests.

In this article, I'll discuss the most important factors to consider when buying an infrared sauna of your own. I've also written a review of the sauna I purchased, a Sunlighten Signature IV far-infrared model.

Why you should trust me

I'm just a normal guy with some persistent back and joint problems. After I decided to buy an infrared sauna I spent over 6 months researching and testing different models in person. I'm unbiased, have no financial arrangement with any companies, and spending several thousand dollars on a sauna is a big expense for me.

Research and methodology

Know the answers to these two questions before you buy a sauna.

  1. Why do you want a sauna – Clearly define what you need before starting your search. Do you want to sweat? Do you want to do yoga? Do you want gentle heat? Do you want red light therapy?
  2. Which sauna can give you that – Once you know what you're trying to get from the sauna, it's time to start your research. I highly recommend searching your area for a spa that has an infrared sauna. I was fortunate enough to find a local spa that had unlimited usage for an affordable amount per month. Afterward, I spent several months renting out their sauna and learning about my preferences.

The spa I went to had a "full spectrum" Sunlighten mPulse (2-person sauna) and an older model far-infrared sauna. This knowledge was valuable in deciding what I wanted. After using these Sunlighten saunas I also sought out their main competitor, Clearlight and used one of their saunas too.

Far infrared is the workhorse

At the outset, it's important to explain that the main generator of heat in an infrared sauna is going to be the far-infrared light emitters.

There is a lot of debate about adding other sources of infrared light to saunas, termed "full spectrum" saunas, which I'll discuss below. However, my conclusion is that these additional light sources aren't worth the money for most people because they don't add much to the experience.

Visible and infrared wavelengths of the electromagnetic spectrum.
Visible and infrared wavelengths of the electromagnetic spectrum.

The easiest way to determine the effectiveness of different energy sources is by testing different saunas. Fortunately, I've been able to do exactly that. First, try a far-infrared sauna and then use a full-spectrum sauna at the same temperature and settings. If you're able to, turn on the near-infrared light emitters only.

What I found, and I think you'll agree, is that there was no difference in experience when you take far infrared light and add other light sources. But when you remove far-infrared light it's very hard to sweat and it feels less hot. This indicates to me that far infrared is the workhorse in any sauna.

"Full spectrum" is a gimmick

It seems like the latest marketing gimmick is to call saunas "full spectrum" by adding other light sources inside the cabin, specifically red or near-infrared light emitters. These can either be built into the wall heater design (like Sunlighten) or as a separate, dedicated heater (like Clearlight).

There is plenty of science behind the use of infrared light for therapeutic purposes. The scientific term is photobiomodulation, but in this article I will simply call it "red light therapy". However, keep in mind that some wavelengths of infrared are not visible to the human eye.

You can read more about the science of red light therapy in this comprehensive guide for beginners.

Unfortunately, saunas companies seem to misapply the concept of red light therapy. Only very specific wavelengths of light have been shown to have biological effects, and only in specific dosages. More light is not always better and may have the opposite effect as intended.

More light isn't always better

It may seem counterintuitive, but more isn't always better when it comes to red light therapy. There is what's called a biphasic dose response, which simply means that too little light treatment won't stimulate a response, while too much light produces inhibition (a decrease in response).

Light therapy has been extensively studied for wound healing, where it results in faster speeding times and less scarring. In a mouse study, for example, a cut was made on the back of mice and then they were treated 30 minutes later with red light (635 nm) of different degrees of energy.

Researchers noted that even brief exposure to red light soon afterward reduced or stopped the expansion of the wound. However, a higher dose of light actually worsened the wound healing – there was a greater expansion of the wound compared to the control group and the mouse would have been better off with no light therapy at all.[1]

In other words, even if these sauna manufacturers had true light-therapy levels of power intensity, it's very unlikely you would want to sit in there for 30-60 minutes because you'd potentially be getting too much light.

Design problems

In addition to the dosage problem, the sauna is simply not an ideal place for red light therapy.

  1. Specific wavelengths aren't used – The science behind red light therapy supports using very specific wavelengths of light. Another reason why the continuous spectrum of a halogen bulb used by Clearlight, for example, doesn't make much sense. If it's outside of the 600-1200 nm wavelength then it's likely just being absorbed by the two main absorbers of light energy in your body: hemoglobin in your red blood cells and melanin in your skin. Only very specific wavelengths of red to near-infrared light are shown to stimulate the mitochondria in your cells.
  2. Light is randomly applied – Full-spectrum saunas aren't applying red light in a specific or therapeutic way. They're just randomly adding it in the cabin, and if you're not sitting in front of the light, or not at the correct distance, then you're not getting any benefit.
  3. You're covered in sweat – Sweat causes a few problems. First, it adds more area that the light must travel through. Red to near-infrared light only travels a short distance into the skin, so a layer of sweat may lessen any effect. Sweat also causes more scattering or diffraction of the light which may lessen the power intensity, which also makes it less likely to have an effect.

Reasons why you might pick a "full spectrum" sauna

The thing about full spectrum is that it's unlikely to do any harm, it just probably won't do much good either. I just don't see it as being worth the money for most people. If you buy a far-infrared sauna, you're not missing anything.

As far as the sauna performance goes, near-infrared emitters replace some of the far-infrared output in certain models, so you may actually get more heat if you buy a far-infrared model.

If you want to experience red light therapy the best way is to buy a dedicated device for that such as the Joovv therapy device that I've reviewed. You want a device targeted at your specific problem or a whole-body device to get systemic effects.

Wood is superior to glass

In sauna design, there seems to be a recent trend towards open glass exteriors as opposed to the enclosed wooden box of prior years. On the one hand, glass looks beautiful, but on the other hand, it weakens the important insulating properties of a sauna.

There's a design principle of "form follows function" but in this case, it's "form before function". Simply put, glass is letting out heat and light energy that could be contained by wood.

For these reasons, I recommend a sauna with as little glass as possible. Ideally, it would be a box completely enclosed in wood with just a tiny porthole window for safety reasons so you could check on the person inside.

What type of wood?

I like basswood because it's hypoallergenic and scent-free. Most companies provide a cedar option as well. You may want to upgrade if it's worth the expense or if it better matches the aesthetics of your home.

Reasons why you might pick a glass sauna

If you're claustrophobic a sauna with more glass may help alleviate the feeling that you're trapped inside a wooden box. Also, depending on your specific use case, such as if you're buying it for a spa or resort, then a glass sauna may better match your aesthetics.

Then again, beauty is subjective and I'm not sure everyone would agree that an all wood (or mostly wood) sauna is less attractive than the newer glass designs.

Heater design and layout

A simple principle you'll quickly learn about saunas is that if you want to sweat then you want as much body coverage as possible. Having a very hot torso, for example, but no heat applied to your legs makes it harder to sweat. Ideally, you would want every inch of your skin receiving infrared radiation.

Unfortunately, many saunas have poorly designed layouts so that it's hard to break a sweat.

Heater design

  • Carbon – This is what you'll find in most saunas. These heaters are thin, wide, and flexible sheets of carbon that produce mostly far-infrared radiation. Sometimes companies will put a mesh or screen in front of the material. They can get hot to the touch, but nothing so intense that I would worry about a burn risk. These tend to be cheaper than ceramic and may emit more EMF.
  • Ceramic – Typically more expensive to produce than carbon heaters, with less surface area. They may also have a higher surface temperature which could increase the chance of a burn risk unless they're properly separated from the user. May emit lower amounts of EMF.
  • Halogen – A bulb that produces a continuous spectrum of red and infrared light and is used in the Clearlight "full spectrum" sauna models for example. These type of bulbs get extremely hot and can be a burn risk, even if you're touching the metal housing of the bulb. For the reasons stated already in the article, a halogen bulb is not an ideal light source for photobiomodulation.

Other Considerations

  • Electromagnetic fields – An infrared sauna is essentially a wooden box with energy sources that shower you in electromagnetic radiation. Then again, so is walking into your local Starbucks. However, there is growing concern that the pervasive electromagnetic and electric fields (EMF) that surround us in our daily lives may be harmful. EMF from human-made sources has increased over the past 50-100 years due to increased use of electricity and new technologies. Thankfully, most major sauna brands are aware of this and have taken steps to shield or reduce EMF. It's not as big of an issue as it used to be unless you're buying a cheap knockoff brand.
  • Marketing jargon and studies – Many of the studies and jargon put out by sauna companies is intended to confuse buyers and make it seem like they have a competitive advantage. Some companies have studies that claim to prove their sauna will cause an increase in core body temperature and heart rate. But any high-quality sauna will do that, even sitting in a hot car will increase your core body temperature and heart rate. Another case is when companies claim unique heater designs that trump all the others. I find these to be unimportant when making your purchase decision.
  • Warranty – This is important to check as your sauna could potentially last you many years. All the major sauna companies I saw had warranties of 5+ years or up to a lifetime.

You'll likely need an electrician

Due to the high power consumption of a sauna, you may need to hire an electrician to install a 15 or 20 amp dedicated circuit. Most of the outlets in your house will be 15 amp (a measure of the electrical draw/usage of the device) except for your washing machine, oven, and other appliances.

Most outlets in your house share the same circuit. That's why if you blow a circuit breaker by using a hairdryer, for example, it might disable the entire bathroom. A "dedicated" circuit simply means that the sauna will be the only device on that circuit.

You may also want to consider the length of your sauna's power cord before positioning the outlet or assembling your sauna.

Final thoughts

As I've laid out above, "full spectrum" saunas are most likely a marketing gimmick and don't do much. Light therapy has solid science behind it, but not the spot treatment offered by a sauna, not at a distance, not with random dosage, and not when you're covered in sweat. Just go buy a dedicated red light therapy device and use it before you get in the sauna.

I've also explained that while glass designs are beautiful, it doesn't serve any useful function in a sauna, assuming you're not claustrophobic. If you are, then you may want a more open design, but you will do so at the loss of the insulating properties of wood.

Based on everything I've laid out above, I recommend a simple far-infrared sauna with as much wood as possible.