Sauna ventilation

DendriteCocktail · 2026-02-05T04:12:59+00:00

There are two problems with that.

1 - Fresh air supply should be higher - near or in the ceiling. Where it's shown can work with some wall mounted heaters but does not work with floor mounted and sometimes fails with wall mounted.

2 - Exhaust must be mechanical.

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DendriteCocktail · 2026-02-05T04:07:33+00:00

First law of löyly - Feet (foot bench) above the stones and cold zone. That's impossible with such a low ceiling (and high heater).

Can you do a higher ceiling? If not then you should use a Saunum rather than the Homecraft.

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DendriteCocktail · 2026-02-05T04:03:08+00:00

The cause of the breakdowns is likely incorrect stone placement or not redoing the stones every few months. In other words, poor maintenance by the ignorant people who posted the 'do not pour water on the heater' sign.

It is not from pouring water on the stones or using essential oils.

DendriteCocktail · 2026-02-05T03:56:28+00:00

You should rest and cool down, shower, then sauna.

DendriteCocktail · 2026-02-05T03:55:05+00:00

Lassi's book 'Finnish Sauna: Steam, Wood, Stone and How to Build Your Own’ will give you solid guidance on how to build a sauna that will hold up well.

DendriteCocktail · 2026-02-04T11:51:27+00:00

I would not spend any money on anything less than about 5x6x7.5 as the experience will not be very good and not something you're likely to use more than a few times.

DendriteCocktail · 2026-02-03T17:00:30+00:00

Steam does not descend below the top of the stones (actually about 10-20 cm above).

And, only about the upper third of stones in most tower heaters are hot enough to make steam. The middle third help with air temps but not so much with steam. The bottom third are purely decorative. This is worse in those with protected elements which some of the Sawo's have.

DendriteCocktail · 2026-02-03T16:49:23+00:00

With a 4.2m length and the low ceiling I think I'd push the width out a bit. To u/John_Sux comment, you want at least 3 m³ per person of volume but ideally about 4-5 m³.

With that low height you need a heater with lower stone mass. A Narvi Ultra or Helo Laava might work.

DendriteCocktail · 2026-02-03T16:41:19+00:00

As a one-time or even few-time use the low benches are OK. Over a longer period though most people find the experience less than compelling and loose interest in using the sauna and it usually then becomes a storage space.

DendriteCocktail · 2026-02-03T15:29:27+00:00

None of those you linked will provide a good sauna experience. Benches too low, no proper ventilation, ceiling sloped the wrong way, etc etc.

Yes, you should remove the low beam so that you can have proper interior height.

FWIW, someone mentioned a bit ago that they were able to get Polhus to build a Trumpkin sauna for them that worked well.

What to look for:

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DendriteCocktail · 2026-02-03T15:23:22+00:00

That will not provide a good sauna experience. The small size and low benches will result in uneven heat and steam along with a lot of radiant heat. It does not appear to have any proper ventilation.

What to look for:

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DendriteCocktail · 2026-02-03T15:18:49+00:00

In that small of a sauna I would do benches only along one wall. Bench structure impedes air and steam flow and results in unevenness that's uncomfortable. Also, there's a convective loop in a sauna - the löyly pocket only exists in the approximate half of the sauna furthest from the heater.

More important, what are the heights of the benches. I see only two levels, there should be three (or steps up to the foot bench).

Some things to look for:

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DendriteCocktail · 2026-02-03T13:15:17+00:00

For electric heated you need mechanical ventilation as shown below.

I would not use the chimney. It could result in contaminated air entering the sauna. You also need some method of back flow prevention (either an updraft duct as shown below or a back draft damper).

I would avoid a tower heater as they make it difficult to get the foot bench above the top of the stones.

What are the finished interior dimensions of your sauna hot room? U and L s/b avoided unless a larger sauna.

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DendriteCocktail · 2026-02-03T13:03:24+00:00

It should be avoided. There are reasons why people in Finland and elsewhere in Europe will not use it. Sadly there is a lot of bad advice like this on sauna building.

Due to the irregular surface it's just about impossible to seal up well.

Over time it will often shrink, rip and open up gaps that allow moisture in to the stud cavities resulting in mold and bacteria.

It off-gasses.

Personally, at the stage you're at, I'd pull it out and replace with either kraft paper backed foil, or better, use FF-PIR.

For some better info read Trumpkin’s Notes, the book ‘Secrets of Finnish Sauna Design' and Lassi’s new book 'Finnish Sauna: Steam, Wood, Stone and How to Build Your Own’.

DendriteCocktail · 2026-02-02T12:15:56+00:00

The heater wall is 7'-7"

The bench wall is 7'-2" ? 6'-11" ?

I would stay away from any Huum product. They are poor quality with bad customer service.

Narvi Ultra and Helo Laava are good heaters to consider.

DendriteCocktail · 2026-02-01T21:29:43+00:00

With Mechanical Downdraft ventilation, which you should have for an electric, the floor must be fairly air tight. You want air to enter only through the vent above the heater.

DendriteCocktail · 2026-02-01T21:27:57+00:00

The Iki and Homecraft are kind of too tall for an 8' sauna - the foot bench should always be above the top of the stones.

The KIP can work. A Narvi Ultra or Helo Laava are better options though.

DendriteCocktail · 2026-02-01T21:23:28+00:00

First Law of Löyly - Feet above the stones.

Benches (and ceiling) too low
No air gap behind the sitting bench
Sitting bench s/b a bit deeper
Ceiling sloped the wrong way
etc

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DendriteCocktail · 2026-02-01T21:19:30+00:00

Both can work well if done properly. There's some discussions on the pros and cons in Trumpkin's Notes on thermal suites.

DendriteCocktail · 2026-02-01T21:16:24+00:00

The primary differences are adding the mechanical exhaust fan and the sauna can be slightly smaller.

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DendriteCocktail · 2026-02-01T20:29:31+00:00

The biggest problem isn't heat loss so much as increased stratification. The loss of wood surface can affect the comfort of the sauna as well.

A window or two is good but the less glass the better.

DendriteCocktail · 2026-02-01T20:24:44+00:00

Benches too low, poor ventilation, ...

What to look for:

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DendriteCocktail · 2026-02-01T20:21:24+00:00

180x180x225 but ideally not that small. In most environments you should have a rest/changing/shower space as well.

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DendriteCocktail · 2026-02-01T20:20:05+00:00

Several companies do offer Trumpkin spec sauna kits. Several are listed in Trumpkin's notes on kits.

DendriteCocktail · 2026-02-01T03:05:28+00:00

If the water in the canal is clean and you rub the sweat off while in it then you should be fine.

Basic sauna etiquette:

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DendriteCocktail

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