Sauna Fogging Up – moisture in sauna bad?

Why Do Infrared Sauna Windows Fog Up? (And Why It’s Totally Normal)

If you’ve ever sat in your sauna and noticed the windows fogging up, you’re not alone. A lot of people see condensation on the glass and worry that something is wrong—maybe the sauna is leaking heat, maybe there’s moisture building up inside, or maybe it’s a sign of poor construction.

In this video, I break down exactly why sauna windows fog up and why it’s nothing to worry about:

The difference between single-pane sauna glass vs. double-pane house windows

Why temperature differences (62°F room vs. 150°F sauna) naturally cause condensation

Why all saunas—cheap or expensive—experience this

Why the only moisture inside is from your own body sweat, not from the sauna itself

Why there’s no risk of mold or damage from this normal fogging process

After testing countless saunas over the years, I can tell you this is a universal phenomenon. Fogged windows are just physics—not a sign of a defect.

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Read the transcript >

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Transcript

Should you be worried if there is condensation inside your sauna? Great question from a group member. I actually get this question a lot. So I thought I would make a specific video for condensation, moisture, the whole theme, you know, glass fogging up on the inside of your sauna.

It’s a perfect day for me to do this. I’m actually waiting for it to warm up outside. It’s 40 something degrees here. And I’ve got saunas, you know, behind me.

And just as an example, because the ambient air temperature in here is 62 degrees, if I were to fire up these saunas and hop in them, though they are dry saunas, they don’t emit any moisture. I think a lot of people have been scared by some type of sauna salespeople or something like that.

Like I’m chilly today, you know, I’ve got a vest on here in the office. It’ll probably get up to 70 today, so I don’t really want to turn the heat on. But the reason why I’m making this a real world example for you is because I want you to understand what causes something to condense, right?

Most saunas don’t have double pane windows like your home would. So there’s less of an internal insulator. There’s no insulation barrier to cause the outer glass from the inner glass to slow as temperature transfers between them. So you have a single pane glass and you have a sauna that’s 150 degrees or 130 degrees inside or 200.

It doesn’t matter what it is. For example, in this room, that would be compared to a 62 degree ambient temperature. There’s going to be some condensing and there’s also going to be some moisture emitted from your skin, like from your actual sweat that creates a little bit of additional humidity inside.

And that also contributes to condensing. So this is nothing to be alarmed of. You can rest easy. It’s very, very normal for every single sauna to condense if you’re getting a good sweat because that typically means that there’s a temperature differentiation between the glass.

and the outdoor ambient temperature that’s great enough to cause condensing. You actually want this to be happening because if it doesn’t, that probably means that the sauna is either weak or, you know, there’s not as much of a temperature differentiator. And you can see this change during winter months versus summer months, meaning sometimes certain times of the year, you’ll get more condensing than other times.

And it also matters if you’re in a sauna that breathes more than others. Sometimes the all-glass front saunas that have gaps between the, you know, door and the side panel, those will behave differently. If you have one that’s really tight that has a felt seal, those are going to behave a little bit differently.

But the biggest differentiator here is the temperature difference in your space versus what’s going on in the sauna. And so I think a lot of people, you know, get worried because the glass fogs up or something like that. Completely normal. You actually want this to be happening.

If it’s not happening, there’s probably not too big of a temperature difference between the internal cabin temperature and the ambient temperature in the room, which is kind of required for you to get a good session. And it’s not going to hurt anything. There’s no issue of like mold or anything else.

These are dry saunas. There’s no moisture emitted inside other than, you know, condensing or sweat from your body. So no issue there. Some people are asking if they only have a certain type of wood, you know, just all the things that can come up.

Most of this stuff is just implanted fears from I don’t know who, but they’re not really understanding the mechanics of why you would have condensation or fog, you know, on the glass inside. But this is why it happens pretty much in every single brand that I test just to varying degrees.

A lot of times you don’t see it because when we’re filming, we have to either clean stuff or bring cameras inside. You don’t see it, but it’s present all the time. It just gives us a really it presents.

an interesting challenge when you’re trying to actually capture a moment or film with a camera lens, because those fog up too. Just like the glass does, so does the camera lens. So it can be really difficult, really challenging to show you some of this footage, because if that’s happening to the windows in the sauna, it’s also happening to our cameras.

So that’s my take on it. If you have other questions, happy to make you videos. Just wanted to let you know, you can rest easy. It’s perfectly normal, happens in every single thing, both expensive saunas and cheap ones.

It doesn’t make a difference.