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It’s not what you think: good venting actually makes your sauna feel hotter

It makes sense to think that you want to keep you sauna hot room tight, with a minimal gap along the bottom of the hot room door and very well sealed walls. And this is partially true.  We want to contain heat.  We want the heat to resonate in the hot room with good, dense lämpömassa  (think heavy stone wood fired pizza oven vs lame ass thin metal toaster oven).  

But with venting, I’ll be the first guy to admit that I used to build my saunas tight, trying to contain heat within the hot room with minimal air gaps.   Then I went back to Finland.  In Finland, the pros call for about a 10-15cm gap along the hot room door.   You crazy?  I was always thinking a gap for a mouse, tops. But 10-15 cm? My cat can fit under that door gap.  

And what about wall vents? It makes complete sense to install them and have chutes for opening and closing, but truth be told, I wouldn’t open the wall vents much. My thinking was, to really crank the heat, shouldn’t we keep the wall vents closed?

No, no, no.  

Once again, as with many things in life, the opposite is true, and the Finns are right.  (Insert political argument about education, health care, public transportation and/or salmon soup here).

How is it that a well vented sauna can feel hotter than a poorly vented sauna?

Any idea?   

Need a clue? 

Ok, try this: ever stood outside on a frozen lake on a sub zero calm day?   Not so bad, is it?

Now, compare: ever stood outside on a frozen lake on a sub zero windy day?  You don’t last too long, do you? “The wind blows right through you, it’s no place for the old.” – Fairytale from New York, The Pogues.

Wind chill will kick our ass. 

Follow this principle with sauna.  

A well ventilated sauna creates air flow (circulating good heat).   Instead of wind chill, a well ventilated sauna creates a hard to notice yet gentle breeze of heat.  

You won’t necessarily feel it, but a well ventilated sauna will feel hotter than a poorly ventilated sauna as warm air is passing over our bodies on the sauna bench.  A very subtle yet slight hot… breeze. 

You can probably sit in a poorly ventilated sauna for a longer time than a well ventilated sauna. What’s worse is that in a bad sauna, you will leave the hot room wiped out, exhausted because you’ve been breathing stale, poorly oxygenated air.  

What do we do if our saunas are poorly ventilated?

Two things we can do:

  1. Let’s pop in a couple wall vents. Borrow or dig out a simple hole saw and drill out a couple holes. Set in dryer vents and flash around the inside with chutes.  The mobile sauna shown here illustrates wall vents..
  2. Let’s make a wider gap along our hot room door. Unpin your hot room door, lay it on saw horses, and cut off a couple inches along the bottom with a skill saw.  
Infinite Cedar sauna vent / chute cover slider
Sauna hot room vent with custom made chute for easy open/close action

Yes, it is counterintuitive 

Good venting actually makes our sauna feel hotter.  

And good venting helps keep our saunas fresh and smelling clean. When we apply the Bake and Breathe method, along with good venting, our saunas don’t seem to be needing to be cleaned much, if at all.

You can read about the bake and breathe method here.

You can see a wall vent being installed here:

So, It’s not what you think: good venting actually makes your sauna feel hotter. And good heat makes all the difference.

Sauna Deco’s larger, hotter hot room.

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38 thoughts on “It’s not what you think: good venting actually makes your sauna feel hotter”

  1. hey Glen, I’m building my sauna as I write this. My wife is Finnish and I’ve fallen in love with the sauna… my question is about venting…

    My stove was originally going to be on an outside wall, but if I put it there I wouldn’t be able to have 1 full bench on one wall… my stove is home made with a water tank off the side with a water jacket… can I put it on an interior wall, and keep the original vent on the outside wall? It would be about 1.5 feet from the stove… or should I vent into the changing room? I haven’t cut a hole yet so I can move vent location if needed…

    Thanks,

    I love your website!

    Lance

  2. Lance:

    Glad you are enjoying saunatimes. As to your venting situation, just put in your vents wherever you can. I like venting from hot room directly to outisde. But, it’s not a big deal if you want to put a vent in your interior wall to changing room. But also, put in another vent in your changing room wall to the outside.

    Use the chutes as detailed above. I really like that you can have vents in multiple spots and just control them how it best suits your hot room. Every sauna has its own soul (ask you Finnish wife about that) and good venting helps the soul come alive.

  3. Hi Glenn,
    I have a question not related to ventilation but to wood storage. I came across this cute picture on pinterest (see https://www.dwell.com/collection/bath-and-spa-aba71657/6122818467279704064 ) which shows a wood sauna with a wood heater and tons of wood piled next to the bench. I’m wondering if this is actually recommended. Won’t the wood turn too humid to keep using it? It’s just for the purpose of the picture, right? Thank you, Claudia

  4. Claudia:

    Spot on. Storing wood in the hot room is not recommended. It’s like storing potato chips in the hot room, with the bag open.

    That said, it’s common to keep a few logs along the floor in the hot room for the spontaneous sauna stoker in you. Especially in Winter, where losing the rock paper scissors contest on the bench, to see who has to go get a log, is that much more of a drag.

    Now, more than what you asked, in this Sauna Talk episode with Daryl Lamppa, a foremost expert on wood burning by a country mile, he commands that wood should be room temperature for best burn. Which makes sense, as we don’t want to be tossing in icebergs into our sauna fire box. So, truth be told, in Winter, I store about 1-2 saunas worth of wood in my hot room, and cycle it in from my outdoor wood pile, down low. Then, with the bake and breathe method, it does pretty well in there staying dry for when it’s sauna stoking time.

    Hope this helps!

  5. Hi , I need some help.
    Last year we found a cheap sauna heater on Kijiji and picked it up , we have since converted an old shed into a sauna and are looking at hooking it up.

    we realized that we would need to wire it but it seems all the electricians around have no idea how to wire it.
    we have the heater and a little panel that was given to us and a sticker on the heater giving us information.

    “A genuine home spa product” ( seems its a company no longer around from the 80’s
    model HE-75 ( cant find anything online)
    serial# 15360
    Volt: 230
    Amps: 32.6
    Watts: 7500
    Phase: 1

    what kind of thermometer do we need to be able to run this thing? it has 2 bigger black wires and one smaller white wire.

    Thank you for any replies it would really help us.

  6. Hi Glen,

    Love your site and the online book. I am in the process of converting an old 6 x8 shed in the backyard to a sauna.
    The only problem with the shed is it has no sheathing . Just a tarpaper wrap and some nice beveled cedar siding. Will that still work or should I re-sheath and re-side. ( I live in Washington State.) Also for venting can I use those little circular metal vent disks that they install after blowing in insulation. Thanks,Brooks

  7. Hi Brooks, glad you love the site and that my book is helping you.

    As to your questions, yes, and yes, and yes! tarpaper is just fine. beveled cedar siding is the bomb. and yes about the vents. Any way you go, above is a really easy and constructive way to vent your hot room. And you’ll get bonus points for making and installing chutes for open/close user friendly ability.

  8. brooks, got a buddy in seattle who has an outdoor unit with tarpaper (roofing felt) and cedar exterior, been a rager for years. as for venting, those metal discs ‘work’ but venting is all about square inches of free air space. you’ll need several of those little discs to get an effective total surface area for free air movement.

  9. Glenn, love the site and have your e-book. Building the sauna this summer and doing a lot of reading on your site.

    Venting question. For best results would you want flow in=flow out (door vent sq/inch to equal wall vent sq/inch)? Or is it more a preference thing?

  10. Mike.. .im sure there’s some science to it, but I install vents by feel. Every room is a bit different, yet the general feel is a generous crack along bottom of hot room door and a couple vents up high, say a foot from the ceiling, opposite wall of door. And these vents have chutes, like in the photo above. Chutes are closed during heat up, and we open them at will when we sauna.

    3x air exchange and the pros in Finland will approve.

    And if anyone wants to wrestle a better vent design than this, i’m all up for it. I’ve vented every which way from Tuesday, and the above system, I like.

  11. Hi Glenn,

    A construction/ventilation question for you…

    Should the back of the cedar panels be touching the foil vapour barrier or separated by an air gap?

    I’d read somewhere else about fixing battens over the barrier first and then panelling to the battens so that the wood can dry out more easily from both sides and any condensation drip down the Vapour barrier rather than Soak into the wood

    Any advice about this and if the same goes for panelling Walls and ceiling?

    Much appreciated
    Alex

  12. Hi Alex:

    Yes, you can do battens to separate your wood paneling from vapour barrier. Yet true be told, I have never bothered with this. It makes our hot room that much smaller, and it creates a gap that in my opinion is best not to be there. I have saunas built over 25 years ago that are looking mighty fine. I think moist cedar is miles better than moist vapour barrier, trapped in the dark in some cavity. That’s my thinkin’

  13. Hello,
    I recently sent a message and one comment in your reply was to use the 16 foot wall of my 8 by 16 foot sauna area for the wall were it would be best to place a the door. I was interested in exactly why that was. I was not planning on this wall For a few reasons but I could adjust my plans. Thank you, Daran

  14. Hi Daran:

    Yes, all things being equal, it’s nice to run the door from the changing room to the outside on an adjacent wall. Reason for this is flow.

    As we exit the hot room, and make a turn for the outside door, we leave the cool down room fairly intact.

    Running the changing room door on opposite wall to the hot room door can turn our changing room into a pass through room. A train car effect.

    All this was told to me by a few different architects (not one, not two, but a few) and so I started building my saunas with door to outside along the adjacent wall, and have always appreciated this design element.

    And for bonus, designing the sauna building with a reverse gable to the long wall, we start to incorporate a deck space with overhang, that 3rd space, not which the Starbucks guy talks about for their hanging out in the coffee shops, but the 3rd space so wonderful for sauna – where we can hang out on the deck or garden all misty wet with rain, after a cold plunge or cold shower, and really expand the vibe.

    Anyhow, these are subjective considerations, but I throw them in the mix for you as you are in the planning stage, and no begrudging to anyone who has build their saunas differently, as the best saunas are ones that get fired up and appreciated (vs. remain on a piece of drafting paper and never happen).

  15. To be clear.. are you suggesting vent under the heater on the wall AND vent under the door of 4″ or just a 4″ door gap at the bottom?

  16. Hi Dave:

    Vent along the low side of your hot room AND a gap along the bottom of your hot room door.

    GETTING NERDY: What we’re looking for is good air flow. When one opens and closes the hot room door, we don’t want any air pressure differential. Good air flow from drain, low vent, bottom of door allows our saunas to breathe and for wood stoves get the air they need for proper combustion.

  17. Thanks Glenn! I’m doing an indoor/electric sauna(8KW). So I think I’ll just do a 3×10 vent under the sauna heater, 1″ door bottom gap, and 3×10 exhaust venting. The Drain is hooked up to the indoor plumbing so I get no play there too much. However that’s double and then some what the Manufacture recommends for the venting. Jealous of the extra heat the wood stoves make and give, but this article made me feel comfortable giving my sauna double the recommendations of the Electrical heater manufacture recommendations. Thanks again!

  18. Dave: You got it. This may be getting weird, but as “every sauna has its own soul”, one of the ways our saunas speak to us is through venting.

    Good venting allows us to connect with the soul of our saunas.

    I see venting as an art, as much as a science.

    eg. I was in my buddies horse trailer sauna yesterday, and we were geeking out on venting ideas and options for his unique/custom build. What’s notable here is that it was all field verification.

    We each asked silently, kindly, and respectfully what our sauna wanted to help breathe, and after tossing water on the rocks of his sauna stove (the heart), and letting the silence allow us to connect to the soul of his sauna, the sauna spoke back to us.

    With a 4″ hole saw, and knowing where studs are, vents can be added easily later, after we’ve gotten to know our saunas.

    https://www.saunatimes.com/sauna-culture/sauna-philosophy/does-your-sauna-have-a-soul/

  19. Thanks Glen! Excited to get mine done and meet it’s “soul”. Hopefully, it’s friendly and inviting 🙂

  20. Dave: The beauty of “every sauna has its own soul” is that we can help make it friendly and inviting. 🙂 (insert plug for DIY ethos here).

  21. Very interesting. I feel like calling “bad sauna” it is too colorful, for instance, some ppl may like to stay longer, and the author admit that “cat size” gap under door will change it. Personally, never ever in my life experienced a bad sauna, rather different character of her. Remember my first sauna… real one, with buddies and beer, in Saki, Krym, Ukraine. I met love of my life the evening, obviously it was one of best saunas!

  22. I am wanting to build a Sauna in an attic space that is amazing. We have a large area that is 22ft by 8 or 9 ft. Facing the area we plan to install has the slanted ceiling on the left side. At the back side their is a Chimney. The other side we plan to add a bath room. That is where i am stuck. Would love to send some pics for ideas. Also, venting is what i am concerned about as well.

  23. This is all so helpful. Thank you, Glenn. Your website continues to provide very useful information. We installed our intake air vent below our sauna heater but on the other side of the wall is a shower and we’re worried about having a vent by a shower. It’s a 4″x10″ rough opening. The outtake is located on the opposite corner up high (also 4″x10″ with a closable register cover.) I’m more inclined after reading this to delete the 4″x10″ intake under the heater and just add a nice sized gap under the door. 2-3″ below the 24″ door is 48-72 square inches of fresh air intake (even more than the 40 square inches from the original vent idea.) If you think this is doable, I’m going this direction!

    Thanks again,
    Liz

  24. Liz:

    Glad Saunatimes is helping you.

    Now, with venting, I can get very woo woo. Every sauna has its own soul. It’s up to us to listen to the soul of our sauna, very quietly and consciously, and understand where and how it wants to breathe.

    No rules, no snarky jibber jabber from know-it-alls on Facebook, no ventilation schematics from sauna companies.

    Some tools to help you listen and feel: A candle. Move it around your hot room. Watch where the flame wants to go. Silence and solitude, to help you connect more to your friend, your sauna. A libation of choice, to help you relax and lose yourself and be present on the bench.

    You are a sauna builder, and you’ve created a soulmate. Your health and wellness retreat.

    In this moment, Liz, I am sure you will know how your sauna wants to breathe.

    I know you can do it. 🙂

    I know you can do it.

  25. Great article Glenn.
    We are building a sauna and we plan to have it well ventilated as suggested. The firebox will be fed from outside the heat room so there will be a limited amount of air exchange due to draft. Were going cut off the bottom of the heat room door as suggested.

    My question is where did you get those lights? Those are exactly what we are looking for.

  26. Hi Glenn,

    We’re in the process of building a small, rustic sauna and have got to the stage where we’re sizing the door and thinking about vents, and I’m not sure how to proceed. We don’t have 2-level seating, just a bench with our feet at ground level. The sauna is an outdoor sauna, with no changing room, just a hot room with a door to the outside. If we have a 2″ (or similar) gap at the base of the door, won’t our feet freeze? We’re in Nova Scotia Canada so it will get cold! I want to get the venting right but I don’t want to create any bad drafts that make it uncomfortable. How do the Finns deal with basic one room outdoor sauna venting? Thanks!

  27. Izzy,

    In all my travels around Finland, I’ve never seen a one room outdoor sauna. All have pre-rooms or often called cool down rooms or changing rooms. You will have to do what you can. If you search “ventilation” on this website, you will get more illustrations of vents. I recommend vents with “chutes” so you can open and close. You can close during heat up., and open most of the time in operation.

  28. Hello Glenn
    I’m planning on building an outside sauna roughly 9ft x 6ft on a purpose built deck in Australia.
    The deck will have small gaps between the deck boards as per a normal deck. If I build without flooring, will the gaps serve as adequate incoming ventilation that the article mentions if I put vents in?
    Also the joists of the deck are pressure treated pine (the newer non arsenic kind), should I be concerned about that at all?
    What do you think?
    Thanks
    MJ

  29. Hi MJ:

    1. Deck with small gaps. For sure. Assuming that you have air flow underneath, like a standard purpose built deck, you will have plenty of air flow, and no lower vent needed.

    2. Pressure treated pine. Well, if this were my sauna, I probably would stain this material or paint it with Kills or something like that, and then, maybe, put a cedar duck board atop. This may be overkill but to me this would be a good compromise. I’m sure there are folks who would never have treated lumber in a sauna, but if these are the same folks that don’t drive automobiles or drink beverages out of plastic, well, then they sure have a point. But this treated material is way down low, and sealing it or covering it up to a good degree would give me peace. That’s just my thought. Good sauna MJ!

  30. Hi! I’m in Northern MN and have the same issue as the Nova Scotia fellow above. Single room, small barrel sauna, and cool feet! I was thinking of installing a small electric fan somewhere in the barrel to get the warm air to flow all around. Is that a viable option, even though it’s definitely non-authentic? I do have vents, but when I open them I can see the cold air dribbling in.

  31. Hi Glen,

    We like your website!

    We built our sauna with Tylo heater a year ago. When the heater tries to reach the temperature above 184 F, it turns off and we have to wait 20 min to reset it. Our sauna has one in vent under the heater and one out vent in the corner across the heater under ceiling. Vent’s diameter is 4 inch.
    Do you have any ideas or suggestions how to fix this problem?
    Thank you in advance.
    Alex.

  32. Alex,

    You can try messing around with the location of your sensor in your hot room. Forgive, as I am just now getting electric sauna heater training, so i’m still a little inexperienced with good troubleshooting at this time.

  33. Hi Glen,

    Your website has been very helpful and I have thoroughly enjoyed many of your podcasts – thank you!

    I am about to embark on my first sauna build. I have done a lot of research and believe I have a good idea of what needs to be accomplished. I will be using an electric heater, since it is going in the basement of my home.

    The dimensions that I am working with are: H 85″ x L 85″ x W 66″. I believe the following bench heights may work best, however I am open to any and all suggestions. *Note I am dropping the ceiling from 96″ to 85″.

    44” ceiling to top bench.
    17” from top bench low bench.
    18” from low bench to raised floor.
    6” raised removable cedar floor on top of tiled flooring.

    The one area where I have found it hard to gather information is regarding mechanical ventilation. I want this sauna to be as close to perfect as possible. Do you have any recommendations on what fans (brand/model) I should look into?

  34. Josh:

    It’s super crazy timing you are emailing me with this question. I just got back from Finland from a “ventilation quest.” I can’t recommend anything specific today, but I will have very specific, proven suggestions for you tomorrow.

    One thought. Your build will probably have the sauna heater adjacent to a common wall (vs. an outside wall). I suggest (in DIY spirit) that you install what you think to be a simple, basic bathroom fan. Odds are that this will be just fine for sauna adaptation purposes. If it fucks up or isn’t the right way to roll, we can switch out this fan and reinstall a more suitable piece of hardware.

    I am hugely interested in this. Please email me your process. And let’s take pics. This work you are doing is part of the more ambitious project that Saunatimes is spearheading “taking back sauna in USA” and one of the slices of the authentic sauna pie is good ventilation (and shame on the bullshit industry for not making it clear.. or understanding it themselves).

    Sorry, i’m on a rampage.. but when you experience the disconnect between sauna in Finland, and sauna in US and A… well.. you can’t help but get Borat like about it. (and i’m not even talking about light bulbs being called “sauna”).

  35. For the guy above with the barrel sauna. Yes I use a 6ich usb fan to circulate the hot air down to your feet. In my barrel I bought 2”x 6” redwood and raised up one bench. This puts your legs online with the stones and easy to put your feet up on the bench across the way.

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