Why a Window in the Sauna is a Good Idea
A Sauna Door With No Window at All
The only time to build a sauna door with no window at all is if you are living with your in-laws and you can only build the sauna in their laundry room. In law underwear: “ugghhhhhh” (voice of Simpsons’ Sideshow Bob after he gets hit with a rake).
A Sauna Door With a Full Length Window
This setup is best reserved for a very public sauna, or a very private sauna. Full length sauna door windows work in health clubs because they create an open feel to what is beyond: usually a pool area. Further, young kids love to stand in front of out swing doors. Sauna users can see everything going on beyond a sauna door with a full length window. A very private space, like Gweneth Paltrow’s bathroom, allows for openness and connectivity to a private spa area. In this instance, there is no concern for nude-ing up and being fully exposed because it is the antithesis of a mobile sauna parked in the middle of a winter carnival. This is a private gig.
I Recommend That All Sauna Doors Have a Small Window
When I build my sauna doors, I like to cut in a modest sized 12″x12″ window. This is in addition to installing a candle window between the hot room to the changing room,. Why? A 12″ square window has feng shui, good karma, and helps those of us with ADD: “Where’s my water bottle”?
We can see through the window in our sauna door with full intention. We look through the window to check the temp, or to see how the fire’s going. With a knock on the window and hand gesture, we silently ask if anyone needs a beer. We can look through the window and spot our towel, or our water bottle, or our sanity. And when it’s all over, we give another knock and wave goodbye, “until next time.” We can do all this and more, without having to open our sauna door.
A window in the sauna door connects the changing room with the hot room in a perfectly subtle way.
A sauna door window represents what we value in life when we are faced with change. Instead of blindly moving forward, we appreciate a peek at where we are going next. Wherever You Go, There You Are, may be Mindfulness Meditation In Everyday Life. And in our case, we can look out before we walk in, and we can look in before we walk out, while still being present with where we are at that moment. Heating up or cooling down. As in sauna as in life: when one door closes, and you are ready to move, look for the window.
What Kind of Glass to Use for Windows in the Sauna
Folks in the glass industry seem about as temperamental as the product they sell. Industry experts that I have spoken with are generally not the most patient and don’t seem like a lot of questions from DIY’ers. Most are more accustomed to dealing with tradesmen. I understand how patience can wear thin as ordering the right custom cut glass can be an involved process. There are many glass options to choose from, and every order involves a careful verification of dimensions. Mistakes are costly.
However, I finally connected to an expert in the field who was patient and friendly, and locked into my barrage of questions. Michelle is a glass industry expert with years of experience. Even better is that she told me “I never stop learning” which tells me that she is open minded enough to keep expanding her knowledge in the field. (This, by the way, is exactly my theory of sauna building, which is why my eBook is open to evolving with sauna builders’ generated content).
For windows in your sauna:
- Plan your sauna window carefully. I am a big fan of transom windows up high. – 16″x 30″ or so. They don’t get in the way with whatever is underneath, and allow privacy. There is the candle window, and window in the hot room door.
- Contact a local glass company.
- Order 1/4″ insulated tempered glass, cut 1/8″ to 1/4″ less than your rough opening.
- Frame in the glass using the same material as your hot room (cedar paneling ripped to size).
- Run a bead of silicone around the inside and outside of window.
Insulated tempered glass is two pieces of glass bonded together. This creates an insulated unit. This system reduces moisture on the glass. This system helps facilitate the temperature extremes of a sauna hot room and a cold winter’s night.
What if the seal of the double pane glass breaks down and moisture gets between the glass? This shouldn’t happen, but if it does, we are shit out of luck. We either have to live with it or replace the glass.
What About Cost?
A 16″x30″ insulated tempered 1/4″ piece of glass costs $93.00. That’s about twice the price of single-pane. But this price is a fraction of the price of buying a window. We build our saunas one time. Let’s use the best glass option we can find for our sauna windows.
When designing and building our own saunas, it’s important to be thinking about windows. In the “ole country” (Finland), with the exception of the candle window, few sauna hot rooms were built with windows. Who knows why. Maybe it was cultural timidity, or structural platitudes, or heat loss concerns. Whatever the reason, today, the hot room window concept is “opening up!”
Like music in the sauna, traditionalists may scoff, but any sauna bather of any origin sweating it out on the upper bench will smile that much wider being able to gaze out of their hot room and take in a bit of nature.
A transom window offers:
- a great vista from the sauna bench.
- privacy while standing.
- natural light without being a fishbowl.
What Size Transom Window Is Best?
Let’s start with 18″ tall by 36″ wide, cut in about 8″ below the 7′ ceiling. A sauna with a hot room transom window and a common wall candle window feels airy and nICE. Don’t have these windows? No big deal. We can make it happen with a sawzall or with your next sauna build.
The Candle Window
Hundreds of thousands of traditional saunas are functioning just fine without electricity, along lake shores and rural countrysides of Europe. As most have been around before the introduction of electricity, they have been built free from the umbilical cord of conduit, 12 gauge wire, sub panels, and electrical inspectors with clipboards and frowns.
And with a nod towards zen of simplicity, these structures are lit by the moonlight, the smiles of its users, and most often by a simple candle. A candle in the changing room can provide ample light in the hot room thanks to a simple yet ingenious idea: a window. When building your own authentic Finnish sauna, be it a backyard sauna, cabin sauna, or even an electric stove powered sauna in your basement, consider giving a nod to this tradition by installing a window within the common wall of the sauna and changing room. Your window ledge in the changing room: perfect spot for a candle.
Then, perhaps after a hectic work week, or maybe amongst a collection of close friends, or family, you are free to take a sauna as people have for centuries. No phones, no music, nothing. Just a single source candle, radiating soft light throughout. Illuminated simplicity.
How to Design the Perfect Size and Location for your Sauna Candle Window
- Frame your common wall (the wall between your sauna hot room and your changing room) 16″ on center, as usual.
- Get a piece of cardboard and cut it out to what you think would be a good candle window size.
- Tack up the cut cardboard where you think it makes sense.
- Imagine your sauna benches in place.
- Walk around to ensure you’ve got it in the perfect location.
- Fold or add cardboard to ensure you’ve got it the perfect size.
- Keep in mind views and angles and the wall on either side.
- Mark your final candle window location.
- Sawzall existing stud, if necessary, and frame in for your window, using 2×4’s.
IMPORTANT: Don’t do #9 until you have your glass in hand. Glass is 110% unforgiving. When framing your window, it’s important that the opening is plum and square, and the opening is at least 1/4″ larger than the piece of glass. As you set your glass inside the frame opening, it’s a good idea to use glass little cork glass spacers, so the glass rests on these spacers, and not directly on the window framing.
Above is detailed in the book Sauna Build, from Start to Finnish. I wish you good luck with this and I know you’ll make it work well.
164 thoughts on “Windows in the Sauna”
This may be useful to someone, as I’m currently building my own outdoor sauna, after searching for a well priced piece of tempered glass online, I ended up finding a place in Burnsville, MN that sold me a 1/4 thick tempered glass cut to 24″x36″ for $32 with tax. Check out River City Creative Glass in Burnsville if you need glass. (Again, no association between them and me)
Great topic! Just a few things to add on what Glenn already covered in the above post.
Fixed windows are probably best and easiest for hot room to provide a pleasant view, etc. Functional windows are harder to incorporate into a hot room but are actually very commonly found in saunas throughout Finland. The challenge is finding a properly constructed functional window so that it holds up to the hot room environment – vinyl is probably the poorest choice because it may deform and deteriorate from sauna environment, metal may hold up but will be very uncomfortable for end users to touch or use, wood is probably best so that it is comfortable for the end user to touch when opening/closing. Fixed and/or smaller functional windows are best for hot room in my opinion. Functioning windows in changing room are recommended and always a nice touch – these can be any type of window since heat will not be a factor.
keep in mind that an operable window never seals up as well as a fixed window, no matter how well they are built. for a hot room application on an exterior wall, this isn’t necessarily the end of the world but if you are looking for the ultimate in trapping heat, a fixed will beat an operable every time. of course, any window between the hot room and the exterior is going to be a massive heat sink. this is why the window between the hot room and changing room is an excellent compromise, especially if the changing room has an exterior window such that you can still see outside from the hot room.
I prefer to have an functional projection window that I can open and air and dry out the sauna & leave open when not in use. It is nice to have a window to the outside so you can watch the seasons or a moon lit night. Stay away from vinyl windows as they will crack. I would also recommend a tempered glass although my own sauna has a standard window glass and has survived temperatures over 250°F. If you have a decent stove I would not be too concerned about heat loss from an exterior window as most wood fired stoves (kiuas) put out 60,000-80,000 BTU’s a few gaps here and there won’t mater. However, adequate insulation on the ceiling and foil wrapped walls are a must to minimize heating time.
PS. Another US misconception is that you need to have cedar lined walls. Most Finnish sauna interiors are made from pine or spruce. Cedar tends to encourages mold & mildew growth which reduces the air quality and results in a urine like odor. Cedar is good for exterior uses but the heat of the sauna will dry the wood and minimize rot. My sauna is 10 years old my walls & ceiling are pine and the benches aspen and I use it every week and the wood has not rotted yet.
Thanks for the detailed response. THe follow-up comments are appreciated as well.
basically a window is not needed at all in the actual sauna room (löylyhuone).
the fact is that every square meter of glass in the sauna adds one cubic meter of the virtual volume as well…meaning that u need more power in the kiuas – hardly anybody knows this.
sauna is supposed to be dark, thus allowing saunagoers to concentrate on the real core of the sauna!
Has anyone used plexiglas for a sauna door window or candle window?
Jim, I would avoid plexiglass use in sauna. Looks like it is good up to about 200 F and that is too close in my book. I also hate funny smells in a sauna and feel that plexiglass could have a funny smell when heated. Here is some general data on Plexiglass for further reference.
Good article, but what I figured into our build was the pack of kids who would be using the sauna and change room and the need for privacy between the two, hence, no window in the door, no candle window in the wall. To each his own…
We are putting a fixed wood window with tempered, insulated glass in our sauna. We have been trying to figure out what insulation to use around the window. We are thinking of the spray insulation for Windows but then I worry about fumes although the insulation will be covered up with the foil. Do you have any recommendations for insulation around the hot room window?
Yes, Kathy… i’ve used spray foam around windows with very good success. Yes, all gets hermetically sealed via foil bubble wrap.. foil tape well applied.
the classic ‘great stuff’ foam is rated for exposure up to 240 degree F. considering it will be behind trim, actual exposure temp will be much less than in the sauna, no worried using the product. be sure to use a foam designed for windows or doors. ‘regular’ foam has greater expansion characteristics compared to window/door foam and there is a risk that the expansion could warp the window/door. this is a bigger deal for doors or operable windows so with a static window like in a sauna, you could probably use either kind. for peace of mind though, i would go with the window/door foam.
in my sauna, i just stuffed some fiberglass insulation between the window and frame for the window between the hot room and changing room. hot room side was sealed with foil tape, changing room side had no seal. wood trim covered everything up.
Thanks Glen! We did go ahead an use the Great Stuff product for doors and windows. Should we have used the fire retardant flavor instead? The window is on the opposite side of the room from the wood stove in our layout.
Miller nailed it (as he usually does). I think any flavor Great Stuff works as long as it’s the minimal expanding (great) stuff, so it doesn’t warp the windows. Glad your sauna build is coming together Kathy.
the fire retardant foam is not necessary. the purpose of that type of foam is to slow the progress of a fire from one floor of a structure to another through the various gaps/openings surrounding pipes, wires, ductwork, etc. without the foam, a fire in a basement could easily sneak through unfilled gaps up into the walls of the floor above. ‘regular’ foam doesn’t have the same fire resistance characteristics as the fire rated-stuff. it has to do with how it burns and is not related to temperature exposure. the fire-retardant foam is a building code requirement for residences but doesn’t really apply to a detatched sauna structure. besides, if your sauna is on fire to the point you are worried about fire passing through a window gap, you probably have bigger things to worry about. 🙂
Use Glenn’s recommendation and it will come out beautiful. Keep ing it real Miller, good job.
Wondeing if it is safe to have a window in the sauna room when temperatures get down to -20C outside, is there a danger of the glass breaking?
Great question. I’ve had no problems with heat extremes cracking glass window in sauna hot room, and frankly I thought I would. And i’m speaking as a Minnesotan who can stand outside between rounds in -20c, take a sip of beer, and scratch my head trying to figure out why the glass doesn’t crack. And i’ve built hot room glass windows in a bunch of saunas (I especially like a 36″ wide x 18″ tall transom window). I do have one suggestion, though: as you trim out your glass in the hot room, don’t go too crazy with the finish nailer, so if the glass does crack, you can pull off the trim and window jam and replace glass. Oh, and run a bead of silicone where window butts against cedar trim, to keep moisture from getting down in there.
I am Building a sauna in my house with a (not to open) window to the outside 27″ x 71″. But I am in great doubt what kind of glass to use? Should I use a tempered glass alone and in what dimension – or a tempered and insulated glass with a tempered energy glass in the outer/outside turning of the two glasses?
I would be more than happy, if you could help me!
John: Great question. I’ve been brewing with a follow up post on this topic for saunatimes, but i haven’t yet been able to get a definitive word from an expert in the glass industry. Thicker glass to hold up to temp. extremes is good. Tempered is good for a sauna door, in case the glass were to break.
Thanks a lot Glenn. Please let me know, if you get some Word from an Expert.
Best of saunatimes!
John: I’ve got more clarity from an Expert: https://www.saunatimes.com/building-a-sauna/the-definitive-word-on-what-kind-of-glass-to-use-for-windows-in-the-sauna-i-can-really-see-clearly-now/
Thanks a lot Glenn. This is really helpfull!
All the best!
Thanks a lot for going into all the trouble getting a competent answer to this important issue!
All the best,
for those not wishing to fool around with framing in a window, sauna supply companies offer complete windows. these are made from tempered glass, available in different sizes/colors (e.g. tinted but costs more than clear), different wood (cedar, aspen, etc.), beveled frames for water runoff and typical come with trim pieces. set in place, a few nails and done. this is what i did with my build. i have a clear window between the hot/changing rooms. window cost me $170 (w/o shipping) and for me, the extra cash was worth it.
Good clarity all the way around.
Good info, Glenn. I went with a vinyl slider in the hot room. One pane is currently cracked and the frame of the slider warped a bit during an especially hot session. It’s still functioning, but eventually I’ll replace it with a tempered wood frame window.
I acquired a 2×2 double pane window glass. I was worried about breakage as it is just above my 6kw heater…two years now and works like a champ.
My 36″x36″ sauna window developed two top-to-bottom cracks recently, after the sauna temperature reached 210 degrees. It was only about 32 degrees outside at the time. The cracks are only in the inside pane, but there is some displacement of the glass and I’m worried it might fall in if accidentally bumped. Does anyone know of any product I could put on the cracks as a temporary measure? ie. high heat silicone? I’m worried about investing in another window in case the same thing happens again 🙁
i’d go with silicone for sure. And then when it comes time to replace the glass, consider breaking up the 36″x36″ window into multiple (smaller) panes so the chances of cracking will be less and if your window does crack, it’ll be a smaller piece and that much less of a pain.
Building a cabin is very similar to building a sauna. This Youtube video extols the virtues of bubble foil. Watch this before building a sauna.
I absolutely agree, transom windows in the sauna add another level of pleasure-the view outside. It was mandatory (X2) in our sauna build!
Thanks for this informative article. The use of a transom window in a sauna is a nice feature, since it offers light and vistas to the natural world, while providing some relative privacy, compared to a conventional sized window.
We aren’t building a changing room, but I love this idea. Thanks!
Alain: You’re right on about the newish trend towards “big glass” windows in our saunas. Thermal pane technology is allowing for some pretty large windows. The inside of a hot room can be 200 degrees f. hotter than the outside, making for a seemingly impossible temperature extreme and tolerance for glass to be able to handle. But this is all possible thanks to the advent and invention of thermal layering, as you point out. I”m not exactly sure if triple pane is the answer. As this is an important, and fairly expensive element to your sauna, my advice is to get with a glass company, explain your application, and have them “spec” the window for your sauna. This way, they are somewhat on the hook to help ensure you get the right glass for your sauna application. Good luck, take pics! send our way.
I’ve been seeing pictures of modern saunas with very large windows and even patio doors, is this ok ? I guess vinyl is out of the question , should they be triple pane glass ?
I just finished a 8×12 ft. outdoor sauna and took it on its maiden voyage tonight and it works great! The Only problem is my large 3×5 ft. window has developed a long crack on the upper part of the inside of the sauna and not sure why? This is what i have
(1) piece at 60″ x 36″ converts to (1) piece at 59 3/4″ x 35 5/8″ Rough Opening dimension
(1) piece at 60 1/4″ x 13″ converts to (1) piece at 60″ x 12 5/8″ Rough Opening dimensions
(3) pieces at 14.5″ x 14.5″ converts to (3) pieces at 14 1/8″ x 14 1/4″ Rough Opening dimensions
1″ OA and will include low-e
I had an option of tempered or Annealed and this is what the glass place told me.
“Annealed is when if something breaks the glass, it breaks into shards. Tempered is when if it breaks it will break into tiny pieces in order not to cut anyone. 🙂 We had chatted about tempered, but I believe you opted for annealed, as tempered isn’t necessarily a stronger glass.”
Is it possible the window was flawed and they may be a leek? I believe it is warranted but want to order the correct window when replacing. BTW this is just glass i framed it in.
Thanks for your helpful responses!
Bummer Dennis! Glass cracking may be due to the heat extreme or may be due to some too tight application upon install. I’d suggest bringing up the issue to glass expert in your area. They will probably jump right on the heat issue right away, but you will point out to them that glass is used in hot environments all the time. Some sauna doors are all glass, as example.
3×5 is quite an opening. Forgive as i didn’t quite follow with your dimensions above, but after taking out the cracked glass, you may want to consider converting that large rough opening from a 3×5 to maybe 2 @ 3×2 1/2 or something like that, thereby 2 pieces of glass vs. one large. I know it will break up the intended big window look but maybe that’s just too big of a piece of glass? Keep in touch, send a pic!
I prepared and always choose for tempered glass because very durable. Thanks for the information. sounds so great and helpful.
I love the look of the transom window. Is that simply a piece of tempered glass pushed flush up against the exterior trim and sitting on the lower 2×4 of the window opening, and then held in place by pieces of cedar trim on the inside? (with presumably a bead of silicon inside and out).
Chris: you’re right there. Tempered glass cut to fit at least 1/8″ less than your rough opening.Flush up to exterior trim, bead of silicon as you mention, and the only trick is a good measurement to rip your jam to hold the glass in place on the inside. Voila! You got it.
Well worth a read. Got great insights and information from your blog. Cheers.
What materials are best for operating window frames (to exterior or interior/changing rooms)? I guessed and have seen written here that vinyl windows will crack and I presume warm madly and quickly become difficult to operate. Wood with an exterior vinyl clad (important for my environment), I expect would have similar problems.
Full wood frame would rot too quickly in my environment or be ned constant maintenance on the exterior.
I suppose my choice would be aluminum. Although it would become hot to the touch, it would be durable to the interior and exterior environments for a long life.
Heasley: All logical thinking and rambling (and I have been right there with you on all that you mention).
Operating windows in changing room:
Interior wood clad.
Best results with this. I have gone with wood exterior but only to match primary dwelling.
And while we’re talking, Let’s talk about windows in hot room:
The way I have advanced is to not go with functional windows in hot room. We are having great results using fix glass and framing around for transom, candle, hot room door windows.
Need venting? Install a vent.
Need fresh air? Pop open the door for a few seconds.
Rationale: Functioning windows just get all messed up over time (as you mention). Way too much stress from excessive moisture, condensation, expansion (as you mention) and it just gets to be a pain in the buttox region (akin to knots on sauna benches).
So, hope this helps. I like functioning double hung wood clad windows for changing room. Fixed glass for hot room. Oh, and I like a LOT of windows in changing room. Makes the space seem bigger.
Weird question but… Any tips for dealing with the wax drippage? We are in the process of building our sauna, trying to foresee all issues!
I’ve talked with a couple of glass shops and they say there is no such thing as insulated, tempered glass a quarter of an inch thick. They say they can get laminated glass that thick but not “insulated, tempered” glass – when I requested what you noted above, they looked at me like I was nuts! So – is this quarter inch laminated safety glass? Thanks!
laminated is probably the same and should work great. As long as our glass windows aren’t too close to the sauna stove..
What do you have sandwiched in the middle of the cedar planks?
I have made sauna hot room doors a few different ways. This way, using a plywood cut out, sandwiched between paneling, is the best. Holds the form and maintains rigidity, even with 27 years of comings and going with kids and lots of use (photo in pic). Step by step details on how to do this in my ebook (big upsell). Get it here ——–>
Beth.. depends upon the window but my inkling is to try to use it. insulate with rigid foam and 2x2s and fir out that outside wall.
I am thinking of building an interior sauna on an outside wall that has an existing window. Can I use the window? Or should it be replaced with something else? It is a new construction and the window is a Marvin Integrity window.
Great to hear that “Sauna Build: Start to Finnish” ebook has been of awesome help for you. Regarding your question, I built this sauna in photo above, so I know the answer. For sake of clarification to your question, let’s follow the following scenario: say you wanted to put in a hot room vent, and you were standing outside wearing your Troxers, holding a cordless drill with a hole saw, ready to drill into the exterior wall.
Here’s what you’d be drilling through:
1. Cedar lap siding.
2. Tyek house wrap.
4. plywood sheeting (or maybe it was OSB, I forgot).
5. R13 batting (between 2×4 joists).
6. Foil bubble wrap (taped well at the seams).
7. T&G Cedar paneling.
8. Your buddies shoulder, sitting on the upper bench. ouch!
Regarding #2 and #6:
There are those who are worked up about the potential of trapping moisture in joist cavity if using both an exterior vapor barrier and an interior vapor barrier. I am not of this camp. If we build our sauna building and our sauna correctly there will never be moisture or water getting into our joist cavities. I like house wrap because it goes on in with a staple gun in 20 mins and it protects our interior walls from weather elements. I’m up for rebuttal on this, but this is what has worked for me for many years.
Sorry to Hijack this thread, but I have a question about the sauna pictured above.
Did you have to sheath the exterior in plywood and house wrap, or is the insulation right behind the T&G siding?
Ebook has been an awesome help, but struggling with this part of the build.
Miller: fabulously detailed. I will enjoy my hot rounds that much more, and sleep even better tonight. Thanks for this excellent info!
vapor talk, my favorite! ‘vapor barrier’ is a somewhat generic term that is often applied to house wrap, poly sheeting, tar paper, faced insulation, you name it but there are differences between these products, particularly the permeance, or ability for water vapor to pass through the material. bubble insulation or kraft foil paper have very low permeability, very difficult for vapor to pass through. conversely, house wrap has very high permeability. it helps keep liquid water (e.g. rain) away from the sheathing but vapor passes through quite easily. and this is the ideal setup for a sauna. you want to limit moisture transfer from the hot room into the walls and also provide protection on the exterior against rain getting in but that exterior wall also has to breath, which is what house wrap provides. it lets any moisture that finds its way into the walls (and it will, no matter how good the construction is) a way out, keeping the wall assembly dry. so while there is a ‘vapor barrier’ on both sides of the wall, it is fine and a quite standard building technique. it would be a mistake to not have anything on the exterior and just put the siding up against the sheathing.
vapor ‘barriers’ on both sides of the wall become an issue when both sides have a low permeance barrier, something like bubble wrap on the interior and, say, plastic poly sheeting on the exterior. this is not a good arrangement as any moisture that finds its way into the wall cavity will have a very hard time getting out, can lead to mold/rot issues.
1/4″ combined thickness.
Question – is the 1/4″ thickness for EACH pane in the double pane insulated window, or is that the combined thickness?
Mira: You’re treading on difficult territory. Infrared cabins are not built to sustain the type of steam and heat produced in a real sauna.
Suggestion: start over. Invest in my ebook ($20 donation). If you don’t have a very clear path toward your own AUTHENTIC sauna, i’ll be happy to give you your donation back.
Happy to help you along your journey.
I am planning to buy an indoor infrared sauna ( which is built from pieces ) and I would like reshape it for outdoor sauna – insulate it. Would you be so kind to help me how to do it? Thanks
It may be overkill but the windows I had made have 1/4 inch panes with a 1/4 inch gap between. Working very well as a transom in the hot room as well as a candle window and door window.
I’ve fallen in love with sauna bathing in the last few years, and realized as we were starting a bathroom remodel that I could fit one in….though I have some issues, in that the place I can put it has a lot of glass! I’m scrambling to figure out the details so the contractor can proceed, and I would so appreciate knowing if it’s not going to work, before I build it! I’m having such a hard time finding advice.
The interior dimensions will be 6’w x 6’d x 7’h. It will be 43% thick, tempered glass (2 full walls and a window). Said another way, besides the roof and ceiling, I’ll have one full wall of wood and another wall with a 5’w x 3.75’h window. The window is an operable Marvin window with unpainted white oak frame.
And one more issue I see, is that the only place my heater can go is underneath the window. I could bump up the size of the heater, but would that endanger the window?
Are there any good rules to follow regarding the amount of glass? I’ve loosely heard that up to 50% glass is acceptable, but others that say it’s too much. I really would love to have this sauna, but because of my constraints, I can’t design it with more wood. What do you think?
Thanks for any help!!
What I am thinking: there is that great line: “constraints are often blessings in disguise, as they get us to think more creatively.” So, in your case, if I were undertaking this project myself, i’d be creatively sensitive to two things:
1. Temperature of glass above your sauna heater.
Once you decide on your sauna heater, i’d play “stump the dealer” and ask them what the radiant wall temp is xx inches above the heater. If they start shuddering or stammering, ask them to refer you to someone cool who has recently purchased and installed the same heater, then have them get a laser temperature gun on the wall above their sauna, and then you’ll know. With that info. then you can go to a non-phone-it-in glass supplier and ask them about temperature tolerances of that glass, and see if your numbers are in sync.
2. percent of glass relative to overall hot room.
The issue here is OUTSIDE window. Experientially speaking, outside windows are cold, as we know. I’d be calling Marvin (they are a MN company, so you’re sure to find someone nICE up their food chain) and start by asking them what the temperature tolerances are for an exterior window such as yours. These folks get paid to be cautious (much like the building inspector and insurance man), so you may want to qualify your question with some framing up of the situation like, “not holding you to this answer but…” or “if we were hanging out in your backyard having a drink, would you…” to help derail them from the employee soldier marching minimize liability corporate speak.
Hope this helps,g.
Glad the book and this website is helping you with your own sauna build.
Re: 3/16″, yes, unless you’re talking a huge window, this is adequate thickness. I’m not a fan of double pane as it’s vulnerable to trapping moisture over time, potentially. Such a great time to be building a sauna !
I found 3/16th’s tempered glass on craigslist. jwill that be thick enough? Or maybe I should build a double pane framed window? (not sure if that’s advisable).
I’m only at the planning stage and your book and blog articles are immensely helpful. I’m sure I’ll be asking more questions. thanks in advance for your knowlegable answers.
25 x 10 are the size. Really, how much heat do you lose with single pane tempered glass. I’m deciding between one or two windows side by side. the sauna size is 8 (or 7.4) by 6. Great time to stay home and build. 🙂
I like your thinking!
1. Depot Foil Bubble wrap:
Yes, very astute! I arm wrestled with the manufacturer on this issue and can sleep at night with this analysis. If a hot room is, say, rocking at 220f, the t&g paneling is also very hot, yet it does create an insulation and heat break from front to back. As much as 60f. Now, this is good in theory, but in practice, i’ve tested this. I recently fixed a sauna I had built and it was heated by a beast of a stove (Kumma). As I peeled back the boards, I saw no degradation of the foil bubble wrap, so the wood insulation theory is affirmed. And one more thing on this, if it’s still a bit of a question, I recommend sourcing regular foil vapor barrier, not the more readily available foil bubble wrap. This product has no poly or poly bi product in its composition, so it should be rated higher than 180f, but I haven’t checked. Please let us know how you shake out with this.
2. Hard wood on walls.
hmmm… Let me sleep on this one. Just because i’ve never seen it, doesn’t mean it’s not doable. If I had the stock laying around, i’d consider the ceiling for sure. Yet the walls? If you were to bump into them or put a hand on them, maybe you’d regret using that material. I just don’t know for sure. Maybe others can chime in on this one?
If using cedar backrest and benches would using a hard wood like maple on the walls and ceilings still get to hot and ne uncomfortable ? also I was wondering about the vapor barrier I used a home depot product its looks like foil bubble wrap but it says it’s only rated 180 Fahrenheit should that be sufficient?
Is flexi glass advisable to be used in the window?
no. Use real glass.
I am building a unique sauna with 3 solid walls and one window wall. The windows I have found came out of a large residential building near the ocean so they should be tough. The glass is 5′ X 6′ with a metal frame, and is double pane. I do not think it is tempered but not sure.
Was thinking about using 2 of the windows to have an inner and exterior window to make and additional air space from the cold outside. I am worried about the glass cracking and it being unsafe. Do you think this is too risky if it is not tempered glass?
Any advise would be appreciated! Thank you!
Adam: Love the creative thinking. My only advice with uncharted territory is to cover your path. In other words, i’d advance with what you’re thinking, as it seems plausible and reasonable as a thought or idea. However, if something messes up, like moisture between the glass or it cracks, or something bad happens, think about how, during the construction phase, you can allow for something to mess up, and a plan to fix it.
Eg. I would install the windows with easily removable trim or not nail in the flanges too much. Test run your sauna for a season or two. Chances are, all will work fine, in which case, you can calk and seal your trim and be done with it. But, if something goes wrong, you can pull the windows and frame in for a smaller window or come up with an alternative plan.
That’s what I love about sauna building. Once your sauna is functional, you can start using it, and feeling out your unique elements. The journey to good sauna is the destination.
building my own toaster oven box, no changing room, sitting outside on concrete slab.
to reduce insulation loss-i’m going with a fixed ‘transom’ window that will be approximately 34X10. I’m heading towards double or triple glazed but wondering about application of reflective films on the interior of the glass? what about breather holes or inert gas fillings-anyone with insight or experience on this?
I have a free 12″x48″ triple pane vinyl transom window. Would you use it on a new sauna build?
You can use this but vinyl will get compromised over time. I have a vinyl window in my cabin sauna hot room – not recommended – but built in 1996 and it’s still basically alive and kicking. And there’s the concern that moisture can access between the panes over time, but I haven’t had this happen, or seen it happen.
If it were my sauna, i’d probably use it, as it is free and you’re looking at it. I would apply your trim around the flange on the outside so that I could access and pop off the trim without wrecking it, and get at the window for replacing it, if things go south.
Thank you for your kind words and advise. You really revitalized my passion to build my sauna. I was getting a little caught up in the details. The suggestion of building in a way to allow me to easily modify key features if something happen to the window makes perfect sense. Thanks so much for your time!
Building an earth-bermed decagon shaped sauna here (6 sides are bermed and 4 are exposed. Thinking of a small functional window on one side (that also has wood pocket shutters)… anyhoo, do you think a small window about 12 or 13” square would warp and need constant repair?? I have a friend (and skilled wood worker) who installed a small functional window in another sauna that seems to have held up well. Any experience?
Sounds like a great project. As a general rule, i like fixed glass windows in the hot room, vs. functional windows, and controlling the ventilation through a couple vents with “chutes”. That said, I do have a bunch of experience: my cabin sauna has a functional window that has held up fairly well (built in 1996). Wood clad is the way to go, so hope this helps!
Hi Glenn —
I will be putting a transom window in a sauna with two L benches (room dimensions The height of the ceiling is 84″ (i.e. 7 feet), and the top bench will be at 36″. I have a 48 3/4″ x 30 3/4″ push out awning transom from a friend that would be great to use and free. Unfortunately, due to the existing room and orientation, the window will have to be behind the long bench.
Is it common for windows in saunas to get too ho /reflective and make the backs of anyone sitting on the upper level bench uncomfortable?
It’s a great window, I just don’t want to accidentally carve a 4 foot portion of a 9 foot bench into a “hot seat”, and not the good kind.
What do you think?
With a window behind where people sit, what will happen is that people will generally not lean back against the glass. And when they do, you’ll be cleaning your glass. Yes, it’ll get hot, especially up top, but it is what it is, as people will generally conform to the situation, my experience.
Thank you, Glenn! The book, the site, the feedback all such a help.
What about a skylight? Can it be done?
I am building a sauna in a corner of my basement that has an existing glass block window to the exterior. Will glass block be able to with stand the heat of the sauna — especially considering the cold temperature on the other side of the window ?
Love the question and valid concern. I helped another person do exactly this, and they said all is well. But this was a couple years ago and either all is still well, or the glass cracked and he ran away from further communication, so his testimonial is not proven.
Intuitively, my hunch is that you’ll be fine. It’d be nice if this glass block window were to have a window in it, for ventilation, but that’s another matter. If it were me, i’d advance the project and sauna on.
If the glass block window proves to give you trouble, either cracking due to thermal shock and awe or too cold of a thermal breach, well, i’d deal with that after. (being mindful of how many nails in the trim around your window so you could get after it from the inside if you need to replace).
Good sauna is the driver here.
Let us know how it rolls!
Hi there from Lake of the Woods, Canada! We are building a sauna with a large fixed window. Do you have any insight into how far away our wood burning stove should be from our double paned window? We are worried that the heat will compromise the glass I.e. break it, but we haven’t seen any commentary on this. Thank you! – Kay
Amazing timing on this as we just finished a really high end top of the line sauna project here in Minneapolis. We worked with Marvin Windows (close to you!) who didn’t want to take too much ownership to providing a 5’x6′ fixed glass window for our hot room application. We bought it anyway, tempered high end stuff, and are advancing the ball.
Many saunas are being built with larger glass window features, so we have our fingers crossed. SUGGESTION: as you install the window, for year one, don’t nail completely the exterior trim around the window, or use screws. after a good long Lake of the Woods winter, you’ll know how well your glass holds up, and if it cracks, you can take out the window/glass and replace with a super high temp tempered option.
I’m wondering about using a single pane of 1/4 inch tempered glass (36”x48”) that I have laying around. (It was intended to be used with a railing unit, but we were delivered the wrong size). Would that work, or is it better to go with a true double pane window. We will be using it in update NY, where it will be very cold outside.
My advice for you is “go for it.” Use the glass you have. I have often used 1/4″ tempered for sauna builds. Transom windows, window in hot room doors, etc.
The one trick, though, is when you flash the outside of your window, don’t set your nails flush, for the first winter. Or use screws. And maybe go easy on any calk. Just feel it out. If your glass is going to crack or not be adequate in terms of double pane thermal insulation, you’ll know before Thanksgiving, and you’ll really know by Christmas.
Then, come Spring, assuming all is holding up well and your happy, you can come back and calk and set your exterior trim for good. If the window cracks or not hold up to the cold/heat, you can easily come back and replace the glass with double pane tempered.
My hunch is that you’ll be fine, but hedge your bet by following above. Lemme know how it goes! and please let me know where in Upstate NY you are… i’m going to road trip up your way this Winter and Spring and mebbe we can sauna.
Hi Glenn, great article. I’m looking to source the 1/4 tempered glass for a transom window like you described. I live near Minneapolis, any input on a reliable glass retailer that could help in the area? Your ebook has been very helpful thus far.
Glad that my ebook, Sauna Build Start to Finnish is helping you along.
Regarding a reliable source for glass, I get a lot of sauna glass from Northwestern Glass in Fridley. https://www.nwglassfab.com/.
For the ” Saunaplex ” I’m building I intend on using 8″ x 4″ glass blocks set in a row with a manufactured ” crawlspace vent ” that is the same size as the block. I’m going with 2 blocks, 16 ” awning vent, then 2 more blocks. They can be siliconed together according to the mfg or just forced tightly together with the provided mouldings…
You see any issues with my idea?
Any rules of thumb, like always leaving 18″ at the ceiling, for use of tempered glazing in the sauna? I have an 8.5w x 9d x 7h with a view. The stove will be located in the center of the room in front of the window wall. Am planning taller windows on either side, shorter window behind the chimney. Granted the wall will not be thermally efficient even with insulated glazing units, I presume the impact is more significant the higher the window.
Right on, Matt. As you say, windows don’t insulate as well as well insulated walls, so we need to balance this. A kick ass wood burning sauna stove is a good way to fight back against the non thermal efficiency of glass. Re: electric stoves, my instinct and empirical whining from the bench is that more KW stove can get you there, but the fight gets harder and harder, and the lämpömassa more and more constrained.
What is your view on push out awning windows being used in hot rooms?
My view on using push out awning windows in hot room, or any functioning windows for that matter, is not a rosy one.
In winter, frost and ice can easily form on the windows and it’s a bitch to close them. And the integrity of the functioning windows get lost over time, in other words, windows warp given all the heating and cooling and wet and dry action.
That said, i’m looking over at my cabin sauna, built in 1996 with a cheap ass vinyl clad window in the hot room, a low end thing bought from a lumber yard as a demo floor unit, and well, this awning window still does the job. The crank is a tad messed up, and you have to push it from the outside to close it completely, but by golly it still provides perfect ventilation and a great view to the lake.
Would I install this same dumb ass window today, if I were building this sauna again, now 24 years later? No.
Is it a big deal that I messed up and used it, at a time when I didn’t know jack shit about sauna building? No.
This is what’s great about sauna.
I’m reminded of my trip to Tampere, Finland. Rajapporti sauna. about 100 years old. Having a beer with the proprietors. He wrote down the word in Finnish, but the translation is something along the lines of…”everything is right just as it is.”
Rajapporti produces fantastic heat. It’s a raggamuffin place. Old, built by Russian soldiers, actually before Finnish independence. There’s a window on the way up the stairs to the elevated hot room. It’s cracked and lost its seal a bit. But there is no need to fix it.
We work too hard in life to try to make things perfect. But there is perfection in imperfection. A good sauna is like this.
“Everything is right just as it is.”
Transom window question…
My sauna 8 X 12 building (outside shell, walls, gables and roof -we’re building our own insulated floor platform) is in the process of being built by a local shed company. I ordered a tempered glass thermopane window from a local glass company (30″ X 18″) to use as a transom window in the hot room. It isn’t mounted or framed in wood, but two glass pieces are mounted with 5/8″ metal on perimeter. The shed folks want me to frame it in wood ahead of time and they will build it into the wall.
Any suggestions on how to mount it in wood? I didn’t anticipate that they wouldn’t be willing to frame the window itself. . Or should I just give them the size and location of the window plus 1/8″ and have them just frame in the window opening, and then get a carpenter friend to mount it when we get the shed here?
Also, after reading the comment about people leaning agains the window, (cleaning it and it gets hot) should I put the location 8 ” down from ceiling height and 20″ in from corner, to avoid that issue? the sauna long wall dimensions are 7′ with an 20″ wide upper bench, lower bench below that.
i like your shed company idea. Get that window on some saw horses and with a table saw and a miter saw, you can build a jam and trim and make that window easy to frame into a stud wall. good stuff!
I like a transom window about 12″ from ceiling and centered within the hot room wall. But I like more to use cardboard and cut out the window and mock it up. Then frame it in.
We are trying to map out of sauna plans. After lengthy discussions on DIY and since we have 3 kids under 7, my husband said no way. has anyone had any experience in hiring a contractor to build a “shed” and providing them the guidance on additional steps to finish it out to sauna level without issues? Any gauge on current costs? I think the original list that is included on this site indicates approx $7k, but is from 2009. We are thinking $7500-9000, but really hoped to keep it under $8000. Not sure if that is realistic.
Please listen to Steve on Sauna Talk. Very relevant. (GOOD) SPOILER ALERT: You can do it for that price, per Steve.
Glenn. I just contacted a local glass dealer. He said they have 1/4 ” tempered glass bit not insulated. Is it the same? Thanks
1/4″ tempered is just fine.
What about polycarbonate panels? They’re multi pane, offer insulating qualities and are easy to work with over glass. Are they okay for a sauna?
Are there any good diagrams or instructions on the proper methods of framing a piece of glass to become a window?
I think using this large shower glass is a great idea. And I hear you about the massive temperature extremes. Here’s how i’d proceed:
1. Install this window.
2. Screw exterior trim around the window (not nail).
3. Don’t calk the trim around the window (just yet).
4. Use your sauna.
If things hold up over the winter, then revisit #3, and apply your exterior calk, to seal it up out there.
If the window fails (cracks), and it should fail early if it’s going to fail at all, then you can take out the exterior trim, pull out your window, and work on plan B, which will be replacing that window with a smaller one or perhaps breaking up the space to install 2 or 3 panel smaller windows in its place.
Regarding too much condensation, I suggest trimming your glass window with Western Red Cedar. This species does extremely well in sauna, under hot, moist conditions. You’ll want to be mindful towards applying a bead of silicone along the edge where the trim meets the glass. This is the seam where water could run down the glass and sneak behind your trim, creating all kinds of yuckiness, which you’ll avoid with that bead of silicone. Blue tape the glass and the trim. It’s worth it. Clean “Finnish”. :).
I have a single pane, 1/2″ thick tempered, glass shower wall that i’d like to use as one of the walls in my sauns. It’s about 4’x8′. ( Yes i know there will be some heat loss there for sure.)
I live in Canada and am a little concerned about the fact that’s it’ll be well below freezing on one side and 100 degress on the other side. In other saunas i’ve build, I’ve used double pane windows, but i have this glass and it’s free.
Do you think i’ll crack? Do you think there will be too much condensation that’ll run down and affect the wood trim that i’d trim it with?
I like your thinking about color matching the windows. It’ll be good for continuity. 🙂
Glenn, I have two 18″x32″ red cedar windows on order from a Sauna company in Wisconsin for my to be built 7x7x8 sauna with a change room of similar size. The sauna and change room will be attached/part of the rest of the building which will be a “she-shed” (the sauna/changeroom is the “he-shed”). The she-shed will have black trimmed Andersen 100 series windows (made of fibrex, stronger than vinyl supposedly) on it.
My dilemma is whether I should/could put a fixed transom Andersen fibrex window in the sauna with a black frame/trim that will match the other windows or should I go with the red cedar windows and perhaps paint/stain the outside of those windows black to somewhat match the rest of the windows? Thank you Glenn
Thanks Glenn, but wondering if I should play it safe and go with the red cedar windows (stained black) made especially for saunas, or take a chance and go with the asthetically more pleasing Andersen window that would better match the main building windows? Bottom line is I’m not sure the Andersen fibrex diuble pane windows are well suited for a sauna environment? Thanks Tom
Hi Gary, and hoping others please chime in. My feeling is that oak is unique and mainly uncharted for any area in the hot room. I’m open minded to the thinking and resourceful to the upcycling of product you’ve milled yourself. Right on to that!
but one piece of advice: No for oak benches. Tight grain and too ouch.
Hey Folks, I live in Newburyport, MA and I plan to build an outdoor, wood-fired sauna this spring. I just used a mobile saw mill to slice 10 oak trees into 1 – 3″ slabs of varying lengths. Will be using for furniture and boat making.
Was wondering if you have any thoughts on using the white oak to frame and finish the sauna? Since I have several hundred linear feet of wood, thought I would use this vs. buying wood. Any thoughts?
Hi Glenn, I wish I read this post before I ordered by sauna. I now have a beautiful fixed window right above the heater. When I pour steam over the rocks, I can see steam escaping out the window.
Is there a way to seal the window?
Thanks in advance!
If you can see steam escaping out the window, then you must have a leak in your window. For many, windows are a good source of ventilation, meaning that a vent doesn’t need to be installed.
So, not sure how to get a good seal on your window. Maybe lock it?
But to make you feel better, i’ve taken many an awesome sauna in Finland with functional windows that are a tad porous.
Right on to this thinking Aaron.
More information here… I can see clearly now.
I’m trying to decide on the best glass for windows in my sauna. I was going to go with insulated double paned glass, but was told that they may have a problem with condensation and eventually becoming hazy due to mineral deposits. Now I’m leaning towards a single pane flush with the inside wall of the sauna, and storm panel on the outside. Do you have any experience to share on what works best?
im looking to build a sauna 6’x8′ with a fixed window on the 6′ wall facing the lake on my property. Ideally i’d like that window to be as big as possible for optimal sight lines, im hinking 5ftx5ft.
Can you advise on what that window should be made out of? What kind of glass? My contractor has concerns about it as i am in Canada and temperatures in the north can go up to -30 degrees in the winter.
please let me know!
I tried warming up the guys at Marvin Windows, Warroad, MN. After some hockey and sauna talk, they still wouldn’t endorse or warranty their windows for sauna. I would try engaging with the glass supplier in your area. Getting their involvement may help with local intel and get them to take ownership.
1/4″ tempered gets expensive, but is often used in the public sauna domain.
Hope this helps,
Converting a cistern in our basement to a 5.5′ x 5.5′ sauna. We would like to add a row of 6″ x 6″ glass block on the top of one of the inside walls. Will glass block hold up to the heat?
Glass block can hold up to heat, but you may want to confirm about how much heat by contacting a glass block manufacturer as I don’t know the temperature ratings.
We want to be sensitive towards heat loss through glass. One row isn’t going to make a big impact, so you should be good there.
I am thinking about buying a sauna with floor to ceiling windows on one wall of a 2x2m sauna. The sauna will be heated by a Harvia wood stove heater. I like the windows because I can capture some amazing views while bathing. I fear though that much glass even though thick, tempered and insulated will cost me heat. However, I’m based in Ireland where tempretures in winter don’t fall too far below 0°c nor do so very often. What do you think? Here’s the link to the sauna I’m thinking about getting (don’t hate cos it’s not cedar 🤣).
When you say:
“I’m based in Ireland where temperatures in winter don’t fall too far below 0°c nor do so very often”
You hit upon the magic differentiator.
We have a thermal engineer on our board of directors, but he is predisposed at the moment and unable to do actual thermal modeling for your exact situation. But as a guy who has taken thousands of saunas, and many in megga sub 0°c, I can tell you that the energy loss gets exponential. So, more temperate climate means that you have a good chance of maintaining good heat with a mega glass sauna hot room.
I am starting the process of building an indoor suana in my basement. The question I have is this: I have a single pane 1/2″ thick 51″ x 80″ tempered glass panel (it was a frameless shower door that I took out from a bathroom remodel).
It has been sitting in my garage for a couple months now, and I am wonder if it would work as a very large window for the sauna. My main concern is how well it would insulate.
I would really appreciate your thoughts.
Love the thinking.
What I would do, and what I advise many others to do with similar inquiry: It’s called the “give it a shot” plan. In your case, it’d look something like this:
1. Frame for this window.
2. Install this window.
3. Don’t trim out the window, or if you do, set a couple thin screws to hold trim in place.
4. Panel all walls except the window wall.
6. Sauna more.
If all goes well, finish paneling hot room, and frame in the window for good.
If your heater struggles to get up to temp., like the little train that couldn’t, well then it’s not the end of the world to take out that large glass panel and frame in for a smaller window.
Before framing for smaller window, I’d test a temporary solution. Insulate and temporary frame what was this large window opening. Then sauna more to validate that smaller window is your solution.
James, all this may sound like a lot of f**’ing around. It’s really not. You’re playing with the house’s money on this one, so it’ll be kind of cool for you to test, iterate, sauna, feel it, change if needed, and that’s often how we make our best saunas!
We are looking to build a small indoor sauna on a tight budget. What are your thoughts on using a full glass storm door and plexiglass for transom windows? We thought the storm door could be cladded with cedar.
Instead of plexiglass for transom windows, consider real glass, as plexiglass doesn’t hold up well over heat/time.
Full glass storm door: Being that you’re talking an indoor sauna, your heat differential is less than the outdoors, so it may work out.
If the full glass storm door doesn’t hold up, you can replace with your own homemade door. The method detailed in my ebook is not too expensive (sandwiching plywood with t&g).
Wishing you good sauna,
I’m considering laying out my cedar tongue and groove vertically on both sides of the sauna door. Would this be OK instead of one side horizontal?
If I skipped the foil and glued both sides of the t&g cedar really good with construction adhesive to the 3/4″ plywood, used finish nails like normal on the tongue. Do you think I could skip the screws? I would still use them around the window. Just trying to get a cleaner look but would like for this door to last for 20+ years 🙂
Yes, for sure Bill.
1. horizontal t&g for both sides of your door should be totally fine.
2. yes, skip the foil, and good glue, like Magnus Bond will hold up forever.
Only thing is to be sure your cedar is acclimated before gluing. I’d cut my boards and take a sauna with them, then make your door at ambient temperature.
With the thermal extremes, we get a lot of expansion and contraction with cedar, so be mindful of that. (another reason why t&g is good material for paneling our hot rooms, the expansion and contraction within the tongues and grooves allow for such tollerances.
Hi, Glenn. Wondering if you have any experience or thoughts on using film treatment on glass to provide privacy? And how that might hold up to temperature extremes inside and outside? We live in Minneapolis and our backyard sauna will have some sightlines to neighbor’s homes. Still want transom windows, but looking for ways to not make it a total fishbowl from the outside at night. Thinking about a tint or mirror treatment, if it’s possible.
thanks, and love your website.
I have my studs on 16” centre’s, does this mean a frame windows to those existing studs or do I add cripple, to support the header? This should be explained and I have looked for this information for a few weeks now feeling more and more special needs all the time!) can you walk me through the stud wall candle window and window door design or tell me where to find this with diagrams or photos for these. Daran
If you have my DIY sauna build ebook you’ll see all this cripple, king, header business detailed (in English, for the casual builder). If you frame for windows within your joist cavities, well, it’ll be an easier road to hoe. If not, a little sawzall action and reframing is very doable, as I’ve done this many times, and first couple times, didn’t know shit from shinola but limped my way through it. And you can too, Daran.
Oh, one more thing. Don’t be afraid to frame everything up, then get some cardboard or pizza box and simulate your windows (and sauna benches for that matter). Field verification at its finest.
Wishing you good sauna action!
Right on Ben, I hear where you’re going and though I don’t have experience with film treatment on glass window for sauna, my first inclination is to apply it outside the window where the intense heat is less apt to mess with it.
I don’t think this stuff is too expensive? Give it a go? Please let us know how it works out.
Hi Glenn. Thanks for writing an article on this! I’ve seen some contradictory info on the right type of glass for a sauna window, so it’s good to get an expert opinion here.
My question for you – have you ever heard of someone putting a skylight in their sauna? As I go through my own build, I’m wondering if that would be an option vs. a traditional window.
Does 1/4″ laminated tempered glass hold for sauna doors as well? We are planning on doing a 16″x60″ lite of glass in our sauna door (that will be right next to the sauna heater. The door opens into a shower room area (not outside.) I called some glass folks in town (Portland, Oregon) and I got some mixed messages back including concern about the lamination melting at such high temperatures. Some were resistant to insulated as well because “the spacers could melt.” What are your thoughts? Laminated or single sheet of tempered glass?
James (tempered shower door topic above) if you are still around, did you eventually move forward with this project and did this work as expected? I’m about to do the same thing here (24×74 x10mm tempered as main door and two 13×74 tempered on each side as fixed window) and wondering if you could provide feedback.
Otherwise will follow Glenn’s advice and report back.
Hi Glenn—can you use argon-filled, low-r glass in a sauna window? We’re doing a 4’x4’ window in our new sauna build. Thanks so much for any input!
Oops. Should say “low-e” glass.
We would like to convert a play house that my husband built (built almost to code when he was dabbling with construction as his after work hobby) into an infrared sauna. I would like to do it for Christmas for him, but admittedly will likely have to ask his advice on a whole bunch of things. He installed 3 plexiglass windows when he built it. Will they have to be replaced? I’m thinking that they may be stronger than glass, and not likely to crack. but could they become toxic? Will they actually get brittle or anything?
The other question is about the wall surface covering. I don’t know what type of verathane he used. I assume that it will all have to be sanded off, as I’m pretty sure that would become toxic with UV light heating it up. Otherwise the dimensions seem like they could possibly work (4.5′ x 7′)
And the last question. I’ve heard we would need to have 240 v line out there. Is there any way to do it with 110 v? My sister had lamps that she used without the extra output. But I don’t know how she did it?
Infrared light bulb closets may work with 110v but that is out of my jurisdiction. I am about authentic sauna, and “The Holy Trinity” of good sauna is heat, steam, and ventilation. Wishing you good sauna Dee!
Having an 8*8*7 built with a 9KW Huum drop heater. It meets the 450 sq/ft threshold for the heater but will have windows on the side.
Did I undersize my heater?
Given that you are in Nashville, I’d say you’ll be in good shape. Not because of all the live music clubs in your town, or because you have a couple awesome Finn’s on your hockey team, but because Nashville doesn’t get colder than a well diggers you know what in Winter.
Many are building outdoor saunas in cold climates using electric sauna heaters. And The Electric Sauna Heater Trade Council (if there was one) would put a disclaimer out there that sauna heaters have to fight like crazy to get everything in the hot room hot, which is what is needed to get the sauna up to serving temp. Imagine a drawing of a choo-choo train trying to climb up a mountain. The train may be able to run fine on level ground (ambient temps.) but the train will struggle on the climb (well digger’s ass temps.).
And what’s worse, is that trying to get a sauna hot with a lame sauna heater with 10 rocks is like trying to heat your kitchen by continually pushing down the lever on your toaster. The heating elements heat air, but the heat mass is what we are after.
Lämpömassa (and all its goodness) can only be achieved with an engine that can.
Hey thanks for this post. I just finished my sauna with two 16×60 tall windows – followed the instructions I found here. So grateful. I’m seeing a fair but of water pooling on the sill. Any suggestions for managing it/preventative measures beyond the silicone? Again, many thanks.
If the water is pooling from a leak, like when it rains, you’ll have to get a magnifying glass and find out where your leak is. It’s crazy how water rolling down the glass can get in there.
If the water pooling is from condensation in your hot room, rolling down the glass from the inside, the best thing to do is consider adding a second sill plate atop the current one, and pitch it a bit away from the glass. And seal it well with a bead of silicone before setting it in place.
Happy to be there for you, Ryan, and hope above solves the water pooling on the sill issue.
Thank you for the very helpful info here! We are just started exploring building an outdoor sauna (not wood burning esp because we already have a sub panel and circuits there), and we have a view to enjoy. Are there concerns about using the brown double pane picture windows from the 70-80s we are about to swap out of our main house? It’d be the perfect size… 48×60. No broken deals, all metal. In fact we will have of these, so I could even save two in a crate for replacements!
Cheers from nearby Seattle WA
Given that you are located in (nearby) Seattle WA, I think you are in better shape using your existing large windows than if you were in, say, Minneapolis MN, where I am right now (-8°f.). That said, as you know, glass is a heat suck compared to insulated walls.
What I would do:
1. Go for it – frame and install your double pane picture windows.
2. Don’t finish off your exterior just yet.
3. Start using your new sauna. Road test it, enjoy it.
If all works, then come back and trim out your windows and off you go. If it doesn’t work out, you can always re-frame for smaller windows.
I think you’re going to come out fine. Matter of fact, I think I have an awesome electric sauna heater solution for you, please email me. And regardless, please let us know how it all works out (with photos).
We had a window between the changing and hot room with a single light bulb hanging there in our old sauna growing up in the UP. I am planning on providing a similar window in my sauna. However, I want to put a vintage looking (electric) lantern there with a small LED bulb which mimics a flickering flame. However, I don’t know if this will provide me enough light in the changing and hot room, although I am sure it would provide the correct ambiance I am hoping to achieve. Have you ever seen this done?
I have not seen exactly this, but I can say from experience that you will most likely have an awesome set up. Replicating the single simple flame of a candle gives off surprisingly good amount of light in the hot room.
“Order 1/4″ insulated tempered glass, cut 1/8″ to 1/4″ less than your rough opening.”
What is the reason for this? Allowing space for any expansion caused by high temps?
I like to use glass that is cut to be less than my rough opening as I have had to come back with a sawzall many times and shave off some framing to fit glass. It’s crazy how that happens. Having a little play in there is just fine. And yes, it doesn’t hurt to have a little play in there if walls expand or move a bit. I actually will use those little cork squares that come with glass, from the glass company, to prop up the base of the glass as it sits in the opening. I figure why not give it a little cushion in there?
BONUS: the bottom window jam. With the cork in there, you can pitch this bottom jam just a tad. Seems to help deflect moisture away from the glass, as it rolls down your window, against your bead of silicone.
Any recommendations on tempered glass thickness for candle and external hot room windows? 1/4, 3/8 or 12 inch.
i like 1/4″. More here.
We’re building a 5×5 sauna in our master bath and are buying Marvin windows for the rest of the project. Marvin tech service said they would not warranty a window in this application (as you know) but recommended a fiberglass frame if I went ahead. I want it to match the sauna (so ideally a wood frame). What are your thoughts on a fiberglass compared to wood or aluminum clad? We’re going to buy a window with a frame. I’m open to other suppliers if there is a specific framed window you think is “the best”. If price is no issue what window would you suggest?
you may be fine with a fiberglass framed window but i much prefer wood. Matter of fact, as you read above, i like fixed glass and making our own frames. Less $ and you really control the action, vs. relying on the glass company framework.
hope this helps
Thanks! The tricky part is it needs to looks close to the other windows from an exterior viewpoint since it’s on our house. Marvin makes a window that is wood on the interior and the exterior is painted aluminum, that may be our best option for matching. I was going to put it on the wall above the heater but sounds like that could be troubling. Would a buffer of 12 inches between the heater and the window be enough?
Hi Glenn, if i get a PVC framed Window , is there a way of building the sauna walls and ceiling around it , so that heat is not getting to PVC? Double the amount of wood at the PVC joints? Also should it be toughened glass rather than double pane? Thanks a mill Glenn
the best hot room window set ups, my experience is to source custom cut fixed pane glass. Either 1/4″ tempered, or if going with a lot of glass, trade up with insulated.
Then, we can frame the window ourselves, using softwoods inside the hot room. I’d avoid any poly/plastic vinyl of any kind. This system has worked great for me for decades.
I’m building a mobile sauna here in the PNW.
Does anybody know about putting stained glass in their sauna?
I haven’t found anything about this yet. I like the idea of a little stained glass in the door.
Yes! Travis, Angler Fish Sauna, and several others have worked with stained glass in their saunas.
1. As you frame in your stained glass window, consider light nailing your jam/trim. If your window doesn’t hold up, it will fail early on, and you’ll be able to back out the window and replace.
2. Alternatively, if you put in a piece of plywood, temporarily, you can sauna with your stained glass window a couple times, to ensure it acclimates, then install it.
I have been trying to work out the specification for an external sauna door for a sauna integrated into a corner of a cabin in the UK. Originally I was looking at a standard double glazed exterior door in an aluminium frame but was worried about heat transfer through the door and possibly the powder coating on the frame becoming promised in the heat.
I was going down the route of finding an alu-clad softwood frame door but spoke to one sauna door supplier who said I should be fine with an aluminium frame throughout as the temperature of the door will average out between the interior and exterior temperature. This would be the easiest option for me (and it would match with all the other doors and windows in the cabin) but I wanted to get a sense check from those in the know! It does sound too good to be true…
I was also thinking not to specify double glazing but single glazed safety glass. The sauna volume is very small (about 4.5m3).
The voice in my head for your situation is “custom build.” Building your own sauna door offers infinite options of window size, cladding material, fitting into your opening etc. It’s not that hard, especially if you follow the plans in my ebook.
But if you want to purchase a sauna door, just be sensitive to square and RO dimensions. And if it’s not a huge amount of glass/window, single glazed is fine.
I know this post is old and i dont expect an answer but figure i’ll ask anyways. I’m building a sauna with a changing room. I happen to have a nice dual pane tempered glass section from a sliding patio door. Would this be ok to use as a “wall” between the heated area and the changing area? it would be a cool modern look that i could pull off fairly cheap/free.
I could either leave the dual panes in the door frame (vinyl i’d guess?) or i could pop them out and cut a ‘track” into a 2×4 frame. it would lose the factory seal between the panes of course and any R value from the vacuum.
Appreciate your resourcefulness and the idea of using a glass section from a patio door. I’d go for it as is. build a wood frame for around it. As you set it into your rough opening, consider not going too crazy with the jam and trim on one side so that if the glass suffers from thermal shock and awe, and cracks, you can pull it out without too much hardship. My hunch is that you’ll be fine.
I am having a contractor install a sauna into a building we just built. I asked if I could pick up the window (sauna side, not changing room side) so we could finish the siding on the outside. First, it was just a piece of glass 24″x48″. It is 1/4″ thick. Shouldn’t this be double pane? And of course, I’m upset because there is no frame. We can’t install this and finish the siding before he returns (two weeks). Isn’t including the frame for the window obvious? I’m assuming the sauna side of the frame also needs to be done in cedar. I’m not sure why he allowed me to pick up a piece of glass and not a complete window. Regardless, I’d like to order a proper window but haven’t seen any sites that accommodate this size or list custom sizes available. I’m not sure how the contractor would view this, but it is my sauna so my decision. Any suggestions at this point?
We build our saunas one time, and get to enjoy them the rest of our lives. Please note that this apparent setback may be a blessing in disguise. Please read this post click here, and especially the comment section with Wayne, where we talk about the advantages of fixed glass vs. window …
I know glass is the big topic here and I’ve been reading everything I can but haven’t found this answer. My local glass companies are saying that they only have single paned or double paned tempered glass. Is double paned the same as insulated tempered glass? Should there be a visible air pocket in between both panes of glass? Sorry if this was covered already. Thanks in advance!
There are basically two roads to go down with glass and sauna:
1. Single paned
2. Double paned.
2a is double pane insulated. This is where a glass company can sell us an insulated window of same thermal qualities as these big ass windows you see now in more modern home construction.
1. is those thick(er) glass that you see in modern spas, often as an entire door or wall.
#1 has less thermal properties, and often we need a bigger hammer (larger more Kw stove) as if you were to put your hand on the outside of this glass in sauna, the glass is pretty warm. So this glass can be a heat sink. Not a huge deal, but it can be a consideration.
#2 is much better in outdoor applications where the temp variations can be quite extreme.
#2 can be tricky as there is some chatter than with a lot of heat, the glazing that holds the gas between the layers of glass at point of manufacture can fail.
For me, I like a less than large hot room window, using a thicker single pane piece of glass for hot room application. I like to frame around it with a water resistant wood species like cedar.
If going with a big ass open glass look, for sure, one should be graduating to thermally insulated.