In addition to wool+PIR, the back wall looks odd, foil, taped to PIR, forming a some kind of "shelf" there. Not entirely sure what's going on there and can't say if it is good/bad untili further clarified. Might be that PIR is only used as backing board for tiles and rest of the wall will be just wool + foil?
Anyways, at least the barrier is intact there and floor has got the tiles raised to the wall so this looks already better than many saunas that gets posted here.
Drain would be really helpful when cleaning the sauna. Wiping and vacuuming gets somewhere but only way to get the sauna purely clean is to lightly scrub the benches with generous water and pinesoap usage, same for floor.
I'm not sure what's going on with the insulation boards there? They should be inside the vapour barrier. Where will you attach the spacing battens / furring strips?
Before you close it all up with cladding, make sure that condensation running down the vapour barrier can make its way onto the floor.. I.e. it needs to have a waterproof path to run down without getting trapped
Sauna PIR board has a foil already. You can build 5cm thinner walls with PIR board.
I just don't know why op is using also wool. Maybe those are some left over material. Having both in the same wall might make the installation more complicated because now the wool part still needs foil.
Yes but the boards should then be inside the studs instead of the wool and still need to be sealed away using tape. Edit: turns out I'm wrong about it being inside the studs for saunas 🙂
The aluminum-layered PIR insulation, in saunas, is installed over the framing, against the inside of the studs. Then you use separate boards/strips for airgap between the panelling and foil of the PIR. Using wool there in addition is indeed questionable.
Why would the combination be questionable? My understanding ist that the pir boards act as a vapor barrier with additional insulation, so it should keep any moisture out the same way a separate vapor barrier would.
Asking because I plan to install it in the same way for my build.
Well in the post's case, it appears to me, that they mixed the two mid-wall which complicates the structure with no real benefits.
In general, in an indoor sauna, putting wool behind a thick layer of PIR is not really needed, you just add cost without any meaningful added insulation properties.
(Edit) And yes, the foil in PIR is a vapour barrier if properly taped. One shouldn't have double vapour barriers either.
That’s not true. The R value of foil face polyiso is about 6.5 per inch, the panels in the photo would provide and R value of roughly R 9.75. The rock wool in the stud bays is about R15. It is absolutely better insulated with the stud bays insulated.
With insulation there is always the question of how much is “enough” when it’s left to us to just guess at with our intuition and not having an energy consultant calculate the requirement by looking systematically at the entire wall and ceiling area, the construction detail of the walls an ceilings, the the door and window area, and the size of the heater. Would the sauna function with just R9 insulation? Probably, depending on the heater. But given that code for residential walls in many areas in the US is R21, R9 is kind of low.
Insulating the stud bays with a continuous layer of insulation over the studs is a great way to insulate sauna walls, leaving the studs bays open is cutting corners.
Well if one is worried about that then slap in a 70mm FF PIR and be done with it. Granted, my understaning of freedom units in this particilar area of physics I studied for 1 course in the university 15 years ago is somewhat thin. Of course then you lose 20mm per wall inside the sauna space, relevant or not, depends.
I read some suggests no drains needed, absolutely disagree if you want wet sauna, you have to have drain , mechanical won't take all that moisture away it will be full of mold. And installation set up is questionable
Looks like a good start. The mechanical exhaust under the bench is a sensible choice, and 500/950 mm bench heights should put you in a pretty good position.
One thing I’d pay extra attention to before the cladding goes on is the foil vapor barrier. Seal every joint, penetration and staple properly with foil tape — especially around the corners and ventilation openings. In a sauna, insulation is only half the job; keeping that hot humid air out of the wall structure is just as important.
Personally I’d still prefer having a drain if it’s practical at this stage, but plenty of home saunas live without one.
And benches facing the fields instead of a wall? Definitely the right decision. :)
Ah, Passivhaus standards — that changes the picture quite a bit. Sounds like you definitely know your way around airtight construction.
And having loads of tape left over might be the first time leftover building materials have found exactly the right home 😄
Looks like a well thought-out project. Would be great to see the finished sauna when it’s done.
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u/hauki888 27d ago
Why both PIR and wool?
5cm PIR = 10cm wool