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Bubble wrap: sauna building secret #5

Building a sauna without using foil bubble wrap is like building a shower and tiling right on sheet rock.  It may work for awhile, but at some point it may very well get yucky.  When you are offered such a wonderful product, it’d be a shame not to use it.

Foil bubble wrap

  • is easy to apply: just use a staple gun and staple it to your studs.
  • is easy to work with: foil tape your seems and around light switches, etc.
  • performs fantastically: heat gets radiated back into your sauna and it creates a superior vapor barrier, protecting your structure and isolating moisture and loyly.

Foil bubble wrap is finding applications well beyond sauna.  It is an emerging building material that you’ll be seeing more of, in more practical applications and uses.  Foil bubble wrap automobile?

Home building centers sell foil bubble wrap in the insulation department.  Here’s Ace Hardware’s offer.

 

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27 thoughts on “Bubble wrap: sauna building secret #5”

  1. Hi Iam building a sauna. Was wondering about the bubblewrap it says its not rated for over 180 degrees. I know that is hot but couldn’t parts of the sauna get that hot. I will take some pictures. I probably put it on the bottom parts where it is cement block. Thanks chris

  2. Where did you find the spec information regarding 180 degrees Chris? I am looking for materials to construct an insulated version of a barrel-type sauna and was thinking about this product.

  3. Yes. Foil bubble wrap is the best, my opinion. And it is readily available. Some use straight reflective foil wrap, without the bubble behind, and this is great product too. I like the Depot / Menards big box availability and ease of use with the foil bubble product. Just me.

  4. Can anyone comment about the use of foil-backed insulation (as a vapor barrier and additional insulation) between the studs and the interior cedar T&G for a sauna. It would replace the foil vapor barrier.

  5. Eric: You can use this yet I prefer the foil vapor barrier as it creates a complete vapor envelope of entire hot room. Foil backed rigid is good, but you have exposed wood studs, and potential minor air breach between joists (studs). Best to cover everything with foil reflective vapor barrier when conventional frame building our saunas.

  6. Yes, we foil wrap over insulation. Unwrapped insulation is best. And be sure to foil tape the seams and around fixtures, etc.

  7. Hi Glen, I’m using an aluminum coated paper available here in Canada which is a fraction of the cost (10c/sqft). No plastic content which is great.
    I’m an engineer with a background in thermodynamics so I did my homework on the bubble wrap and couldn’t find any tangible benefit to justify the cost.
    We’re using lots of your ideas from the book and hoping to have our sauna complete for Christmas so thanks!

  8. Camm: Thanks for the input. Aluminum vapor barrier is a great thing. (reflective and moisture barrier). We tend to go with foil bubble wrap as it is readily available at big box Depots/Lowes/Menards here in USA. Your no plastic content is a bonus. Further, your product lays flat, making t&g application that much easier. (it’s a bad move to overlap foil bubble wrap). Send me a link to the mfr. if you have it. I’m interested.

    More importantly, you being an authentic sauna enthusiast AND an Engineer with a background in thermodynamics, would you like to join our Lampomassa Analysis Committee (LAC)? LAC meets semi annually at the LAKe (my cabin) and you have to pay your own way, but I make great post sauna food. If interested, I’d look forward to reviewing your LAC application, which is a 50-100 word essay on your thoughts and comments regarding:

    https://www.saunatimes.com/sauna-culture/sauna-philosophy/could-lampomassa-become-the-second-finnish-word-to-be-adopted-into-the-english-language/

  9. Does it need to be bubble aluminium? Or will just aluminium wrap work? Also, I have tyvek, the outside plywood is up already, while I wasn’t looking! So should I put the tyvek on the inside now before insulation? Can it go over the 2×6’s then insulation? Can I use sided insulation? It’s what I have… So I have bare exterior walls showing with the studs from the inside… Should I cover them up with tyvek before insulation? Then Insulation, then foil? Thx Brad

  10. One more idea… Seeing how I did not get the tyvek on before the exterior walls… Should I still put it on there? Can it go over the studs on the inside? (I cannot get the plywood off the outside now to get it on there right…) What about the sided insulation? What would hold up non sided insulation? Wouldn’t it just fall down over time? Can I use sided insulation and then the aluminium wrap? So from inside it would be starting with the exterior siding on already bare plywood on bare studs… Should I put the tyvek on first, then insulation? sided? 2×6 walls… Then last the aluminum wrap then cedar tongue and groove?

  11. I forgot the ceiling… that also got put on without the tyvek… So it’s raw rafters with raw plywood already on it… Shall I put the tyvek up first before insulation? Or maybe the sided insulation with side up against plywood then foil? I need some direction obviously… THank you…

  12. Hi Glenn,

    Thanks for the invite, we’d love to come and visit the LAKe cabin to share ideas over some Löyly and Lämpömassa (I also installed radiant floors in our house) to see how its really done! I’ll get onto the essay and get back to you soon. Our sauna is up and running now, we easily get 100 deg C in our hot room with the temperature outside at 20 below. We’re yet to put the finishing touches and complete sealing it, but our lives are already better with our little oasis!

    The product that I used on the walls under the cedar is Scutan (https://www.atlanticcoatedpapers.com/products/vapor/) it comes in rolls that are 50 inches wide and very easy to work with, especially if you have two people. In Canada, I got it at Home Hardware, not sure if the other box stores carry it. If the corners are too tight when you come to installing the cedar, you can easily cut the paper and tape to relieve the tension as you go.

    For Brad above, the Tyvek goes on the outside of the building under the siding, it allows the wall cavities to breathe and prevents moisture from the outside getting in. You don’t need Tyvek ceiling, however, you should have some form of

    On our sauna we have the following layers from outside in:

    Lap siding (pine), Tyvek, Aspenite (chipboard), 1 inch foiled solid foam insulation, Aspenite, 2×4 stud walls with pink insulation, Aluminum paper vapor barrier (Scutan), Cedar tongue and groove.

    The aspenite and solid foam provides additional insulation and a continuous vapor seal which may be a little over the top!

  13. not to my knowledge, no, yet if you hear of something or have a VOC meter and want to test, please reach out!

  14. Hello there!

    I am currently building a sauna just outside Ottawa, Ontario, Canada. We have 80 C seasonal temperature differences between winter and summer. I am building a 6×8 woodstove sauna using concrete “deck blocks” and 2×6 subfloor joist framing with a 1″ treated plywood subfloor sheathing. Given that the subfloor is raised off the ground using concrete deckblocks, how should I insulate/vapor barrier/air barrier the subfloor under the sheathing? I will use Alu foil on the inside of the walls of the sauna UNDER my tongue and groove cladding but how should I vapor barrier the floor under my plywood subfloor? Should I place Alufoil directly under my subfloor, then insulate, then tyvek facing the “cold side”? Any information on how floors should be properly insulated and CORRECTLY vapor tight/breathable if need be would be greatly appreciated!

    Looking forward to my first sweat.

    Cheers!

    Samuel

  15. Samuel:

    Your on the right track. I would use 2” rigid between floor joist cavities flush up to subfloor before laying your subfloor.

    And to prep your floor, this is where I will up sell you and encourage you to click the button on the upper right part of this website and invest in my ebook. In there, you’ll get a detailed explanation of how to do this right. And as a bonus, you’ll get details on many/all other nuances, a few of which I think will really help you along.

    And as an extra teaser, please search “vinyl cement” in the search bar above and you’ll get a super amateur video documentation of another nugget of empiricism.

    Happy for your build and hope this helps!

  16. Hi,

    Great to see this community here!

    My concern about this bubble foil as a vapour barrier is that it might off-gas in these high temps.

    Your thoughts?

  17. Mike:

    If this is a concern, you can use regular foil vapor barrier. A bit harder to find, yet find-able.

    I’ve spoken with trade industry professionals about this product. It is rated for temps well North of 200f. This is good as the temp. behind our wood paneling is less, and the temp behind the foil layer even more less.

    But swallowing all this may be like talking to the Marlboro salesman about healthy living, so, again, if it’s of concern, go with the non poly, poly bi product foil.

  18. for reasons glenn listed, the actual temp where the bubble wrap is located within the wall assembly is much lower than the hot room itself so practically shouldn’t be a concern unless you are blasting the sauna at 225 degrees or something like that. the cost difference between the bubble wrap and ‘traditional’ foil wrap is basically the same, i went with that product for peace of mind. the bubble wrap is definitely more forgiving than the foil wrap though, foil is pretty easy to tear, just need to take your time.

    and unlikely most stores will carry the foil wrap, other than specialized construction stores or sauna supply shops. i ordered mine online, lots of choices out there from reputable sauna suppliers.

  19. many use poly as a vapor barrier for changing room. The key is a moisture barrier keeping it away from the joist cavities.

    Re: lämpömassa and heaters, we want to keep in mind that amount of rock is not equal to lämpömassa. Some rock is mainly cosmetic and doesn’t get hot. But you’re rocking, and that’s a good thing.

  20. stephen, if an outdoor unit, you will want to provide a vapor barrier on the exterior walls of the changing room, like any other type of occupied structure construction. foil barrier would work but is expensive/tedious compared to good ol’ faced fiberglass batt insulation. place in stud cavity, staple paper ‘tabs’ to face of stud, done.

    but what about the interior shared wall between the hot and changing rooms? does that wall require any vapor barrier on the changing room side? my advice is NO. foil barrier (the paper or bubble stuff) has a very low permeability, meaning moisture does not pass through it easily. so by placing a barrier on the changing room side of the shared wall, you have now created a ‘vapor barrier sandwich’. any moisture that finds its way into the wall will have a very hard time getting out (and believe me, moisture always finds a way into the wall cavity). damp walls can lead to mold growth and other bad stuff.

    and technically all these products are called vapor ‘retarders’, not barriers. they all allow some moisture to pass through, some just much more/less than others. so on the exterior walls, the house wrap on the exterior side is a vapor retarder but more permeable than faced insulation (typically five times more permeable) and much more permeable than foil insulation (like, 50+ times more permeable). moisture in exterior walls is not as great a concern as it can ‘vent’ to the exterior through the house wrap.

  21. Hi thanks for all the great information! I am currently in the middle of turning a basement pantry into a sauna. I have a couple questions. First to I need to leave a gab between the foil bubble wrap and the cedar? Also the room has foundation wall (concrete) in it. Does that wall need to be covered and insulated or can it remain expose?

  22. Daniel:

    you’re welcome!

    Gap between foil vapor barrier and cedar is not critical. Some apply firing strips and allow for an air gap between cedar and the foil (thermal bridge).
    Concrete wall: for sure, you very much should isolate this from your hot room. Otherwise, you’ll be struggling to heat up the room, because that foundation slab will suck all the heat out of the room. I’d apply rigid foam between 2×2’s and then foil, then cedar.

    Hope this sets you in the right direction!

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