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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.  
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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15 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).

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