Is it time for mechanical ventilation in our sauna cool down rooms?

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How many hours have you spent enjoying yourself chilling out between sauna rounds in your cool down room?

For many of us, if we were to put a pencil to it, I think the number could be greater than many other things in our lives. Could anything be better than our time spent cooling down? For many of us, the cool down is as important as the heat up. A good cool down space is valued and important for equalizing our body temperature and enjoying the benefits from the rubber band theory without jackrabbiting our sauna rounds.

In English, the cool down room is also often called the changing room or poorly translated from German: the anti-chamber. With saunas built along masculine lines, this room may also be referred to as the man cave, dog house, or party room.

Walker recognizes the importance of Sauna ventilation and finding good pure air. And this effort extends also to our cool down rooms (more below).

John’s Wisconsin sauna, looking out into a well ventilated cool down room

Cool down room climate control

For many, we are able to “infinitely control” the temperature in our cool down rooms by simply cracking open the door to the outside and / or cracking open the door to our hot rooms. Yet this action, generally, only controls our cool down room temperatures. Humidity, on the other hand, tends to linger. Especially when it’s very cold outside. On cold sauna nights, we can see a massive amount of steam leaving our cool down rooms, but as our cool down room temperature goes down, moisture collects on surfaces (glass, metal, towels, beer cans). Many love the climate of cool and moisture. It’s akin to a hike in a rainforest. Magical. However, excessive, lingering moisture is not great for our sauna buildings.

Back to mechanical ventilation

Is your sauna cool down room begging for mechanical ventilation? If yes, where is the best place to locate a cool down room vent? Up high makes some sense, as bathroom mechanical vents are on the ceiling, but as warm air cools, it releases moisture as water. Maybe a mechanical vent is best lower on the wall in the cool down room? Here are a couple recommendations from folks who have sat in their cool down rooms longer than many other things in their lives:

Just as in our homes, offices and saunas, there’s a need for ventilation to remove CO2 and other effluent in the vestibule/changing room and shower area. In some this may happen naturally with windows, doors and natural convection, others and perhaps most need mechanical ventilation.
Best is to have separate ventilation for this area and not shared with the sauna. This makes it easier to maintain the best desired environment in each and fortunately the cost for this isn’t too high.
For humidity removal a ceiling mounted exhaust is best (hot air rises, hot air holds more moisture than cooler air…). Combined with a fresh air supply near the floor should work well for both CO2 and humidity removal.
Temp is another consideration. If the sauna has a lot of people coming and going then a higher temp in the vestibule will keep bathers more comfortable each time the door is opened. This especially with saunas that have lower benches or are lacking a significant heat cavity above the door. Otherwise cooler temps might be desirable.
In most a ceiling mounted bath exhaust fan with a fresh air supply near the floor as far away from the ceiling fan as practicable is probably sufficient. The ceiling fan should be mounted near the shower area.

For a quiet solution, consider an inline duct fan, such as from Fantech. And for total silence, you can Install a duct silencer between the ceiling vent and the fan. The fan, silencer, and nearby duct should all be mounted with strap and not have contact with any part of the structure. This should ideally be controlled with something like a Lutron Casetta or TP-Link so that the speed can be controlled and turned off remotely or with a timer.

– Walker Angel, the best name in the Sauna aficionado business

Where I have seen the biggest challenge is in the mobile saunas or small saunas that get fit into existing spaces…In mine, the control is operable doors and windows together with a ceiling fan. The structure itself is both massive and leaky, which I have come to believe is ideal…When it is too cool, I open the hot room door for a few minutes and the fan does a nice job of mixing the air. If it is too warm, we open windows and use the fan to mix the air. Happily, I lucked out. I wish I could say that I planned it all.  

John Breitinger, link to his Wisconsin sauna here.

17 thoughts on “Is it time for mechanical ventilation in our sauna cool down rooms?”

  1. Hello,
    Thinking of building a sauna in my basement with an electric heater. Recently lost access to a wood burning sauna that I loved for many years and building an outdoor woodburning unit is not an option. I miss sauna and am willing to copromise to get it back. I noticed you caution against using pine, yet my father in laws sauna i used for years did have a combination of pine and cedar both in the sauna and changing room. Some of the pine knots in the hot room did have some pitch that had oozed and petrified years ago, but other than that I didn’t notice much difference in the hot room. The cost of cedar may make it impossible to have a sauna. Pine is relatively inexpensive and plentiful here. I’d love to hear your opinions.

  2. Hi Eddie:

    Yes, pine pitch is the main gig. A less expensive option to Cedar can be poplar/aspen, or spruce (used a ton in Finland), or maybe basswood. I’d be choosing any of these three before pine.

    And a guy needs to be thinking air gap with any of these species. And very good ventilation. And drip edge.. all detailed in my ebook. These species need to dry properly between rounds (unlike cedar which, like ducks in springtime, seem to love the wetness).

  3. We are wishing to build a sauna in our newly being constructed home. Do you sell plans for that? It would be a smaller sauna connected to our shower by a glass door, in our master bath, just big enough for 2 or 3. Space to lay down, stadium seating is a plus.
    J

  4. i’m not familiar with them, Mark! Though I’ve installed vents in bathroom remodels and such, sauna mechanical ventilation is a new thing for me. My instinct is to just treat the cool down room as if it were a bathroom, and buy the stuff at Big Box and install it.

  5. I ordered your ebook on building a sauna. I can’t find information for the lower bench height in an 8×12 sauna (6×8) hot room. The upper bench is 44″ from the finished ceiling.

  6. Hi Stacy,

    Yes, 44″ from ceiling, then 18″ down from there. Please type “law of loyly bleacher” in search bar above, you’ll get … oh, this will be easier, click this link here. And this should help you!

  7. We will be building our outdoor sauna for our lodge in Alaska this summer. We are using locally milled Sitka spruce that has been drying for a few years. The floor will be concrete. My question: What do you recommend for sealing the wood and the concrete.
    Thanks much. Your website is a gift of information and advice. The best we have seen so far.

  8. James:

    First, in the Saunatimes promotion department, when you say “Your website is a gift of information and advice. The best we have seen so far.” Can we borrow this? I was in a meeting yesterday with a couple of angels looking to help me and Saunatimes, and I was hiding under my desk de-ego-izing “It’s not about me!! It’s about good sauna!!” So, maybe we can borrow these kind words for future testimonial?

    Ok, now:
    1. Locally milled Sitka Spruce:
    As I shared with another guy who is milling his own paneling from an old cedar harvested from his property: “love this idea. When you are almost done, please give me your address. I’ll show up with my trailer and help load a bunch on there and take some of that beautiful wood off your hands.” But seriously, if you are milling this product for paneling your hot room then definitely do no sealing or treating. “Au naturale” in our private saunas apply to what we wear as much as how we are best to deal with our wood. A well vented sauna, and you practicing the bake and breathe method is the best way to care for wood in the hot room.

    If your question is about sealing the wood on the outside of your sauna, well, for that, I’d circle back with a good local lumber yard in your climate/region. There are all kinds of products for that. Silkens, and such. And i’m big on big overhangs to protect the outside of our buildings.

    2. Sealing the concrete:
    As you’ve probably noodled around on Saunatimes, I’m guessing that you’ve discovered vinyl cement repair. (you can type those three words into the search bar above). This product has been my go to for decades, and mainly in terms of how it works with cement board (Durarock). It’s like peanut butter and jelly in terms of how the two products work so well together. you can get skim coat cement to suck in and seal a floor. But you are asking about sealing concrete. And for this, maybe you can get a second opinion from a cement contractor in your area. My gig is more about creating a thermal break from a colder-than-a-well-diggers cement slab and a hot room floor. That’s where guys like “Ben Square” and Trevor Trowel come in to play.

  9. I am trying to purchase something on your website but it will not let me. It says please fill captcha but there is not captcha to fill.

  10. Hi Glen. I’m converting an 8x 12 shed into a wood fired sauna. I’m in Ontario where it gets very cold in the winter. Am I better off with a large fresh air supply under the wood heater – if I leave a gap under the hot room door won’t I just be sucking freezing air from the outside making my cool down room too cold? Note, the exterior door to the cool down room has a slider window for fresh air supply. Should I add an intake vent?

    Thanks for your advice.

  11. So, Gary, welcome to the rabbit hole of sauna ventilation.
    1. Yes, fresh air intake vent near the heater, to feed the stove and bring air in.
    2. Yes, gap under hot room door, as this gentle blow dryer helps dry our hot room floor as air travels across our hot room floor. For sure, this air movement will create some draw of air from outside into your changing room, but with a window slightly cracked, this action will be a good thing. The cool down room can get super steamy in winter (a very good thing). This climate is welcome, but it’s nice to be able to move that air around too.
    3. Out-vent on a slider in the hot room. You can moderate your air movement this way.

    1-3 above may be all you need to know about venting your sauna in cold climates.

    I will say, one of the real killer attributes you could think about for your sauna is that if it’s tied into electric, consider “warm tiles” or an electric radiant heat system. It’s a living large feature. There’s nothing like coming back into the cool down room from outside after a winter cold plunge or snow angel session and feeling warmth on your exposed feet, just before you crack a beer or a smile, with endorphins rushing and no urgency to get back into the hot room.

  12. Hi Glenn,

    I am planning a sauna build in Houston, Tx where the humidity is generally quite high. Are there any special considerations you would suggest as far as moisture control to prevent mold and help the to dry out the sauna and changing area (i.e .dehumidifier, exhaust fans, AC unit in dressing room) in addition to what you already suggest in your ebook?

  13. Hi Tom:

    The bake and breathe method is a great foundation for keeping things dry and germ free.

    And with an electric heater, a variable mechanical ventilation system is a great way to improve ventilation and also air flow after sauna.

    And building your sauna with details in my ebook will help. Things like drip edge, and slope to drain, gap along hot room door as gentle blow dryer. Etc.

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