Sauna Venting 101: The Best Real-Life Examples (+ Diagrams)
If you landed on this page, you’ve probably realized that you need a sauna vent.
That realization isn’t necessarily a pleasant one, especially if your sauna is already up and running, and you’ve noticed the air feels stuffy when saunaing and/or your sauna doesn’t dry properly after use.
To make matters worse, many sources claim there’s a lot of conflicting advice on sauna ventilation, so what on earth are you supposed to do?
Luckily I have good news and lots of clarifying answers! Do you need a vent in a sauna? Yes, you do, but sauna ventilation doesn’t have to be rocket science and you don’t need an engineering degree to understand it.
I compared what the best sauna heater brands say about sauna vents and found they’re giving nearly identical advice, which means sauna venting isn’t really as conflicting as some sources would have you believe.
In this article I’m going to show you clear, up-to-date sauna ventilation diagrams + video and how my own saunas (indoor and outdoor) are vented: they’re the best examples since (indoor) saunas with electric heaters are vented differently than (outdoor) saunas with wood-fired stoves.
Sauna Venting: Why Is It Important to Vent a Sauna?
I’ll keep this section short so that we can get to the meat of the matter right below. But just in case you’re still asking “Why do I need a vent in my sauna,” here’s why:
😌 It’s essential for a pleasant sauna experience: you get to enjoy the heat and löyly longer when you have fresh and oxygen-rich air coming in.
🔃 Fresh air coming in won’t help if it’s instantly sucked out (through an exhaust vent or a wood-fired stove), so what you need is fresh air mixing with sauna air and circulating. And how do you circulate the air in a sauna? With a functional design and/or strategically placed vents.
🔥❄ This circulating air balances out temperature differences that would be much higher without ventilation: if you’re one of those people who needs a sauna hat because sauna air burns your head and ears (while your feet are cold), that’s likely a result of lacking/completely missing sauna venting.
💧 Ventilation will keep your sauna fresh also in between sauna sessions and protect its structural integrity: humidity and moisture need to be directed outside so that your sauna won’t mold and rot in years to come.
How to Vent an Indoor Sauna that Has an Electric Sauna Heater
Important to realize before digging in: the below works when you have mechanical ventilation in your home. This means we’re talking about an indoor sauna that has an electric sauna heater.
(You don’t need mechanical ventilation in an outdoor sauna that has a wood-burning sauna stove, which I’ll discuss further down the article.)
What this also means is that in most cases, mechanical ventilation is installed by professionals (certified HVAC technicians). That’s the case with my indoor sauna too.
That’s because the “fresh air” sauna manufactures talk about never means air from the neighboring room, for instance, but should come from the outdoors. This means air chimneys (= ventilation ducts) are needed.
Below you see a sauna ventilation diagram taken from the instruction manual my electric sauna heater (Harvia KIP) came with:
A) Sauna intake vent should be placed in this area. It needs to be at least 20 inches (50 cm) above the heater, either in the wall or ceiling. The recommended pipe diameter is 2–4 inches (5–10 cm).
Sauna air is recommended to change six times per hour.
B) Exhaust vent: ideally, it’s placed lower and on the wall under the sauna bench(es), as far away from the heater as possible, steering used air directly to the ventilation duct.
Alternatively, you can have the exhaust pipe even closer to floor level, providing an entry to used air that is then directed into a vent at the top of the sauna.
C) Drying valve (closed during heating and sauna bathing, leads to outdoors through a duct): even some Finnish sources present a drying valve similar or identical to mine as an exhaust vent, but I’m going by what Harvia says, which means a drying valve isn’t the same as an exhaust vent.
Since I have one myself, I can confirm it doesn’t have the suction the exhaust vent in the shower room has. It’s great to have as it helps to dry the sauna after löyly, extending the longevity of your sauna (= no mold or rot forming even after decades), but it’s not the exhaust vent shown or meant in the diagram.
D) Exhaust vent is above the shower in the bathroom right next to your sauna. This is how used air is exhausted if the sauna itself doesn’t have an exhaust vent. For this to work with mechanical ventilation, you need a roughly 4-inch (a minimum of 10 cm) opening under the sauna room door.
Ideally, the exhaust pipe should have a larger diameter than the supply air pipe, but real-life examples show that in most cases, the pipes seem evenly sized.
In my YouTube video above I show you exactly which vent is which and where they’re placed.
For anyone who thinks sauna ventilation is a divisive topic, I have to report that at least the best sauna manufactures (Narvi, Helo, Mondex, for example) have the same recommendations as world-leading Harvia above.
How to Vent an Outdoor Sauna that Has a Wood-Fired Sauna Stove
The nicest thing with outdoor saunas and wood-burning stoves is that they rely on natural ventilation (gravity ventilation), which is perfect for a DIY ventilation system.
Together with the chimney effect and deliberately designed openings/air outlets near ground level, and fresh air being so close by at all times, no additional ventilation is needed, but only IF your sauna is built correctly.
Adding air holes in the floor, for example, can be impossible if you built/laid your sauna on concrete slabs (like so many people unfortunately do!) instead of using concrete blocks as piers.
Below you see a natural ventilation diagram for a wood-fired sauna, taken from the instruction manual my wood-burning sauna stove (Harvia Linear 16) came with:
A) My outdoor sauna gets plenty of fresh air from under the stove itself and floor level in general, thanks to a slatted floor (pictured below), which is highly recommended for outdoor saunas.
B) I don’t have an outlet per se as shown in the diagram but have a window instead; like Harvia states, “the stove itself circulates air,” which means the outlet in this case is meant to work like the drying valve in an indoor sauna.
Windows in general are meant exactly for that momentary drying after sauna bathing and are not meant to be left open.
A window alone can’t replace a dedicated sauna ventilation system, especially indoors where an electric sauna heater is used and mechanical ventilation needed.
Problems with Sauna Venting in the US
If you’ve browsed my website before, you may have realized what the state of sauna understanding is in the United States.
It’s so poor that according to the President of the International Sauna Association (ISA) Risto Elomaa, Americans try to sauna but don’t know how and in most cases in saunas that are built “badly or even worse.”
Now that we’re talking about sauna venting, this statement starts to make sense: in the US, sauna ventilation requirements are nowhere near Finnish standards.
In a typical scenario, a sauna in the United States or Canada:
🔶 has no fresh air coming directly from the outdoors
🔶 isn’t built for löyly and water use even though they are the entire point of sauna bathing; when no water is used, no moisture or humidity will form either (apart from you sweating), so venting is considered optional
🔶 there are no vents of any kind as it’s believed convection alone will take care of everything, which is not the case
🔶 if there is some sort of ventilation present, instead of sauna vent pipes (that are a must in mechanical ventilation), we see mere sauna vent covers and cedar sauna vents that look pretty but don’t necessarily mean much more
🔶 if there’s a sauna vent fan, it can move the same, used air, but obviously can’t bring fresh air in if it’s not connected to the outdoors
🔶 if there are pipes, and “fresh air” is coming from somewhere, it’s stale air from the next room, and in worst cases, sauna humidity is exhausted to living spaces, not truly outside
Even most sauna vent kits in the US are just pieces of wood. They can work as part of natural ventilation in an outdoor sauna since fresh air is just behind a wall, but that’s not the case with indoor saunas with electric heaters that are never good candidates for natural ventilation.
Frequently Asked Questions (FAQ)
1. Does a sauna room need ventilation? Should I put a fan in my sauna?
Yes, a sauna needs ventilation; see above which type (mechanical or natural) suits your sauna best.
Whether you should use a sauna ventilation fan or a sauna exhaust fan depends on a few factors: at worst, a fan just circulates the same air already present in the sauna room, which is not what sauna ventilation means. At best, fans work great if they’re connected to a real ventilation system.
Fresh air needs an entry to the sauna while used air needs an exit. Ideally, all air comes from and is exhausted to the outdoors.
2. Does a sauna have to be airtight?
No, your sauna absolutely shouldn’t be airtight but have proper ventilation instead.
Opt for mechanical ventilation when you have an indoor sauna with an electric sauna heater, and for natural ventilation when your outdoor sauna has a wood-burning sauna stove.
3. Is sauna air good for lungs?
Yes, sauna air can be amazing for lungs, but only when the sauna is used correctly and ventilated properly. In a traditional sauna where you pour water on the hot sauna rocks to produce steam (löyly), the humidity level easily rises to 40%.
Even for asthmatics, the ideal humidity level is between 30% and 50%, and research says asthmatics may benefit from sauna air.
When you don’t use water in a traditional sauna (= incorrect use), the air will be very dry (humidity around 15–20%), which isn’t good for lungs. The opposite is also true: too humid air makes breathing more difficult, which is why a steam room (humidity around 100%) may not open the airways but instead, have you coughing and gasping for air.
4. Should you air out a sauna?
Yes, but “airing out” may not mean what you think. Above I presented a sauna ventilation diagram (by Harvia) where it’s said: “the sauna can also be dried by leaving the door open after bathing.”
This, however, works only if you open the sauna door to the bathroom where you have an effective exhaust vent (that’s piped to outdoors like it should). This is not only true but exactly what Harvia meant too.
No legitimate source would ever claim you should open the sauna door and let the humidity enter the living spaces in your home.
Final Thoughts
Now you should have a clear picture of what sauna venting truly means and whether you should go for mechanical or natural sauna ventilation.
If you haven’t purchased your sauna or the materials for it yet, an outdoor sauna with a wood-fired heater is definitely a simpler choice where ventilation is concerned.
Some people wonder how much ventilation for a sauna is enough. As a general rule, the intake and exhaust vents should always be on/open and never fully closed. Only the drying valve/window is closed during sauna bathing, and the rest you can adjust if you feel a draft.
If you feel the air is fresh, you never experience shortness of breath, and your sauna dries well and fast in between sauna sessions even after throwing plenty of löyly, then your sauna is likely ventilated enough.
It’s also worth mentioning that not all negative symptoms are necessarily caused by poor ventilation. Dizziness, for instance, that some people think is the result of lacking ventilation (which is possible), is still more likely caused by your blood pressure dropping, which is common in the heat.
If you’re worried about heat distribution, mechanical ventilation brings more even heat than natural ventilation is able to. It’s not a problem, though, if you have tiered sauna benches and they are placed high enough.
