The Heavy Fog Sauna Microclimate: here’s one we all seem to love

There are many different sauna microclimates.

That’s one of the things I love about sauna. And we’ll discuss a few of them.

Two rooms can have the same thermometer reading and feel very different. Change the stove, the rocks, the ventilation, the amount and timing of water, the room surfaces, or the way the fire is managed, and you can create a very different thermal experience.

The Heavy Fog is one of those microclimates.

And for many of us, A Heavy Fog is hard to beat.

Start with radiant heat

All the rocks in a Heavy Fog sauna aren’t necessarily glowy and superheated.

Think under 300°F rather than rocks glowing at extreme temperatures.

That means we’re not depending on blisteringly hot stones to instantly turn every splash of water into an aggressive blast of steam.

Instead, there is a lot of sustained even radiant heat coming from the stove and rocks, and the heated mass around it (walls, benches, and our warm Crocs on the hot room floor).

The stove damper is turned down.

The fire is burning steady, rather than raging. Heat is being directed into the rocks and into the room (vs. up the chimney).

Ventilation is natural passive ventilation, and potentially the air is only exiting down lower, between the benches, opposite corner of the stove. The steam vent (by our ears) is closed off. We are floating along with slow lazy river passive ventilation.

The objective isn’t to flush the room with air, it’s to allow the heat to accumulate, in layers. Stratification being a good thing.

Then comes löyly

Lots of it.

This is where we can have some fun. We can introduce water on on the rocks by dosing each rock an ounce or two (the Petri Pour method), like a priest passing out communion wafers, or we douse with a big spoonful right into the meat of the stove. (The percent of water that trickles onto the hot steel is not a good or bad thing for a Heavy Fog Microclimate, but with a kick ass stove, most of the steam is surely from the rocks).

The important thing is that we’re not looking for one dramatic WHAM! of löyly. Instead, the löyly comes on slowly.

It builds.

It gets thick.

Heavy.

Hot.

But not scaldy. Not scorchy. A heavy heat fog.

It’s more like we are creating a fog of steam, or a blanket of steam settling down over us in layers.

And then something interesting happens.

The steam doesn’t go away.

Lämpömassa supports the back end

This is where I think lämpömassa, (thermal hot room mass) becomes the secret ingredient.

The initial löyly wave is generated by the water hitting the rocks.

But the thermal mass of the stove and the surrounding heated surfaces helps support the experience after that initial burst.

The sauna heat and steam don’t go flat. The opposite happens. The sensation builds. And holds.

The heat has legs. Lämpömassa supports the back end of the steam wave.

The steam covers us like a Heavy Heat Fog, and it sticks around. We get to enjoy a long time between löyly. No wet noodle syndrome that can happen when you’re relying almost entirely on repeated löyly applications to generate heat. A kick ass stove with lots of mass, a heavy stove, with the right amount of rocks that all get hot, fire brick, lämpömassa supporting the back end of the wave of steam.

The stove has enough juice to keep providing löyly.

The thermal mass, deep bass radiant is helping carry the tune.

And you don’t need a raging fire

This is another thing I love about this kind of sauna.

You don’t need to stuff the firebox.

In my experience, we’re talking roughly four or five sticks of wood for an entire sauna session.

The goal isn’t maximum combustion.

It’s maintaining the thermal system.

The stove is already hot. The rocks are hot. The room is hot. The mass is hot. Not overly hot, but eternally even hot.

You’re feeding the system, not trying to recreate it every ten minutes.

And after a long Heavy Fog round, the hot room gets a chance to recharge.

Our cool downs are at least 20 minutes, giving the room that amount of time to come back toward neutral before the next round. Rocks heat up, the room freshens.

That’s part of the rhythm.

Heat.

Löyly.

More löyly when you want it.

Cool down.

Repeat.

The Heavy Fog recipe

If I had to describe the recipe, it would look something like this:

Hot thermal mass, ever present everywhere.

Moderately hot rocks.

Strong radiant heat.

Lazy river, passive ventilation.

A stove with enough juice to keep producing löyly.

Lots of water.

And time.

Put those ingredients together and you get something very different from simply turning up the temperature.

You get the heavy fogy fog.

And this is why I think the conversation about sauna microclimates is more interesting than the conversation about bench heights, or the perfect sauna.

There isn’t one.

There are different ways to move heat through a hot room and engage with the body.

Different tunings of the jazz trio of heat transfer (radiation, convection, conduction) and steam.

We’re going to explore some of those other microclimates in future SaunaTimes pieces.

But this one?

This one’s right up there.

The Heavy Fog microclimate is a good amount of radiant heat, and not breezy with too much convection. There’s a shit ton of löyly and we get to enjoy a lot of lämpömassa to support the back end of our waves of steam.