Creating the best venting system for your sauna building is critical. We are happy to visit with a professional builder who is finely tuned to air circulation and proper venting. Enter Bob:
Bob Daigle, Casco Maine
We’ve recently completed the construction of our outdoor / stand alone Sauna. In the process of thanking Glenn for his book & insights, he asked me to explain a bit about our construction technique. In particular, what the air circulation strategy we used.
Full disclosure, we built our own home a few years ago. I have worked professionally as a builder / carpenter, so I went into this with a “build a very tight small house” mindset. Our own home is ICF construction and is incredibly tight. This saves us on heating, but also has serious ventilation consequences. To address this in our home we use a whole house ERV to swap indoor air with outdoor air, replacing the air in our home roughly 8x per day. We monitor our indoor house environment with a Netatmo device (highly recommend). This device measures humidity, temperature, noise, and C02.
I’ll admit, I’m a bit consumed with indoor air quality and ventilation :), and here is the best venting system for your sauna building
Given this experience, from the start of this sauna project, we were thinking quite a lot about air flow & ventilation. This would be a small building with one extremely tight room (Sauna Room) and one adjoining room with less need for “tightness” (Changing Room). The Sauna room changes temperature radically. Further, it introduces large volumes of moisture into the entire building envelope. To me, this combination spelled potential problems, unless proper ventilation was built into the design.
Our solution was to build the structure using the same ventilation techniques we’ve used on houses
The first step was to insulate the walls & ceilings using a proper moisture barrier. In the Sauna room we used batt insulation between the 2×4 studs, foam sealed the windows. We used the Reflectix vapor barrier on walls & ceiling (taped), as Glenn suggested in his book. We also insulated the Changing Room walls. The exterior plywood sheathing was covered in standard exterior house wrap. The entire structure’s interior & exterior was then covered with T&G Northern White Cedar (Maine grown!).
The best venting system for your sauna building consists of a few parts
First, the door leading into the Sauna from the Changing Room has a 1/2” gap at the bottom. The sides & top of the door are sealed using a foam strip in the door casement. The gap at the bottom of the door allows the influx of fresh air, particularly when the stove is operating. This has the benefit of supplying oxygen for the fire. Also, the air gap keeps the floor rather cool & dry, as the air washes over during its’ travel to the stove. (I really notice and appreciate this cool draft as I’m kneeling in front of the stove, mid-sauna, to add more wood).
Secondly we used the same strategy as we did in our own home. The roof was built to provide a 12” overhang on all four sides of our 8×12 structure. A 12″ overhang not only looks pleasing, but it also provides a place to install two 12” soffit vents in both the front & back side eaves. These are simple / cheap metal one’s from the Home Depot. In addition, we installed a Ridge Vent on the ridge of the roof. Again, the ridge vent was simple to install and is inexpensive.
Finally, instead of putting a ceiling on the changing room, we left it open. An open ceiling allows the cool down room to fully participate in the movement of air supplied by the soffit vents & ridge vents. This provides a “cathedral ceiling” effect in the changing room, and also gives direct access to the wood stove chimney pipe going up thru the attic. This access to the attic chimney helped a lot in the chimney install. Also, the open ceiling is easy to inspect. I was thinking about adding a vent on each Gable end, but decided against this as overkill.
The combination of the soffit vents & ridge vents are sufficient.
The result seems to be working quite well
The stove clearly has a strong supply of air coming from under the door. I suspect the stove gains much of its air volume from the soffit & ridge vents when it is really cranking & requiring oxygen. Also, I feel comfortable that any moisture that makes its way out of the Sauna Room is being dispersed thru the vents.
By the way, we are using the “Bake & Breathe” technique Glenn has recommended. We leave the Sauna Room door closed for the night while the Sauna Room is still quite hot. Then we open the hot room door in the morning. We are finding the Sauna Room bone dry in the AM. Then we just crack open the Sauna Room door and let the entire structure breathe until the next Sauna session.
One final point, due to our (my) focus, maybe an obsession?, on indoor air quality / circulation – we’ve installed a Carbon Monoxide alarm in the Sauna Room. We find it reassuring that the feeling of deep relaxation is coming from the heat & steam – not from some bad gas vapor…
Again, a big Thank You to Glenn for his guidance. I stumbled upon his website when thinking about building this Sauna and it has made an enormous positive difference in our ability to do this right. Merry Christmas – – looking forward to the Maine Winter!
Below are a few photos showing the completed structure as well as the cathedral ceiling in the changing room and the soffit vents under the eaves. You can see the roof ridge vent as well.
Thanks to Bob for sharing with us the best venting system for your sauna building!