Kuuma External Feed Wood Sauna Stoves

Selecting the Right Sauna Stove (blog link)

Do I need an 8" or 12" throat?

An 8" throat is typically used for standard framed wall construction. A 12" throat is often used for thicker walls, such as log sauna construction or other builds with deeper wall assemblies.

If you are unsure, measure the total wall thickness where the stove will pass through and contact us before ordering.

What do I need to know about the wall the stove passes through?

Measure the total wall thickness where the external feed throat will pass through, including finished materials on both sides. Standard framed walls often work with an 8" throat, while thicker walls such as log saunas may require a 12" throat. The wall opening must be properly protected with non-combustible materials, and all required clearances from combustibles must be maintained according to the owner’s manual and local code.

Is the metal heavy enough to prevent warpage?

Yes, under normal operation.  Kuuma Wood-Burning Sauna Stoves are manufactured with American Steel in the United States from a combination of 1/4″, 3/8″ mild steel, and 3/8″ stainless steel to form the most durable sauna stove on the market.

Does my stove need to be cured before using it?

Yes, even though we clean it well, there are still residual oils and preservatives on the steel, plus the high-temperature paint smokes a bit on initial heating.  It is best to fire your stove outside 3 times (small, medium, and large) with at least one 3-4′ section of stove pipe “To create a draft.” The smoke is strong but safe to breathe.  See the video on our YouTube page.

Finished taking a sauna, now what?

We highly recommend the Bake and Breathe method (Blog) to keep your sauna stove and sauna in optimal condition.

How long should I leave my draft open when heating my hot room?

The draft should never be left in the high burn position for longer than (5-10) minutes to prevent overheating.  A well-insulated hot room should reach the desired temperature in about 45-60 minutes.  When the draft lever is left in a full-open position, you send all the heat right up the chimney, and it’s not heating your hot room.  It will also severely overheat the stove.  To heat your hot room effectively, you want to lower the draft lever between 1/8th and 1/4 open after the logs are burning well.  This will heat the hot room and not send the heat up the chimney.

Is it approved to UL standards?

Yes, it’s Listed by PFS-TECO to UL 1482 - Standard for Solid-Fuel Type Room Heaters. PFS-TECO is an IAS- and OSHA-recognized Type A Third-Party Inspection Body (ISO/IEC 17020) authorized to certify and maintain follow-up factory audits and labeling control.
Certification is maintained through quarterly inspections, verifying compliance of all materials, components, assembly, and labeling with the approved UL 1482 test report.
Each stove bears a serialized PFS-TECO certification label confirming active listing status and full compliance with U.S. safety requirements.

Plain-English version - Yes — independently tested and certified for safety to UL 1482 standards by PFS-TECO, an OSHA-recognized laboratory.
This means every Kuuma sauna stove is inspected regularly to ensure it meets the same safety and performance standards as the unit originally tested and approved.

Is it EPA certified?

Kuuma wood-burning sauna stoves are designed for sauna hot-room heating, not residential living-space heating or domestic hot water. EPA has determined that the 2015 Residential Wood Heater Rule does not apply to Kuuma sauna stoves as manufactured and intended for sauna hot-room use. Kuuma sauna stoves are therefore not EPA-certified residential wood heaters because EPA certification is not the applicable regulatory category. Commercial installations remain subject to local building/fire code approval, the appliance listing, installation manual, chimney requirements, and any local air-quality rules.

Is it brick-lined and baffled?

Yes, it is brick-lined to prevent warpage and, coupled with the baffle, enhances the burning of gases.

How is the steam (löyly) with the Kuuma sauna stove?

Good steam is a key attribute of a great sauna.  The Lämpömassa behind our design results in awesome steam.  Use only clean, mineral-free water (rainwater or lake water works great) to make steam with your sauna rocks.  We strongly recommend that you do NOT use water with a high sodium content (think what our cars in MN look like versus ones that don’t see the winter), especially if you don’t practice the Bake and Breathe method because salt, heat, steel, moisture, and paint don’t play nice and will result in premature rusting.

Is it an air-tight stove?

Yes, the only air it gets is what you set on the carburetor. The doors are sealed for airtightness.  If you get the glass window, we have an intentional air gap.

The small gap is intentional (Video). 

Do we supply chimney parts?

No. All chimney components can be sourced locally or online.

Your Kuuma stove uses a standard 6” flue.

You will need:

• 6” single-wall or double-wall stove pipe from the stove up to the ceiling

• 6” Class A (double-wall) chimney from the ceiling support box through the roof

• A 6” ceiling support box, roof flashing, and storm collar sized for your roof pitch

Any UL-listed 6” Class A chimney system (Selkirk, DuraTech, etc.) will work, as long as all chimney components are from the same manufacturer.

The stove is designed to run 6” chimney throughout — no reducers or enlargers.

If you use a chimney cap, it must be an open-style cap (click here). This is the one we use and recommend.

👉 Blog post: Chimney components explained

Does my Kuuma stove come with rocks?

No, but we recommend granite or quartz, often found locally at lakes and streams. Make sure they aren’t cracking or porous. Many retail landscaping businesses often sell them as well.  We recommend a golf ball to a tennis ball in size, with a slight variation.  Please wash with warm water and soap before installation if you pick your own. Sauna Rocks

Do we recommend a dedicated vent to draft our Kuuma Sauna Stoves?

Yes,  A 4" low-mounted, dedicated outside-air vent located near the stove provides sufficient combustion air for proper drafting of all Kuuma wood-fired sauna stoves when installed with minimal restriction and a direct path to outdoors.

Can you heat water for bathing while it heats the room?

Yes, water heats very quickly with the optional 12 or 16-gallon stainless steel hot water tank. It’s very convenient for applications without running water.

Can you see the fire?

Yes, if ordered, an optional 5″ x 8″ glass window is available to watch the burn, provide an additional light source, and make your sauna experience even more romantic and enjoyable.

Is the glass window easy to clean?

If ever needed, it’s easy to clean by dipping a wet rag (microfiber) into ash located in either the firebox or ashpan and wiping, followed by drying.

The small gap is intentional (video).

How long should it take to heat my sauna?

Many factors (see blog post) come into play when determining how long it will take to heat your sauna.   What kind of wood are you using?  What material is your sauna constructed out of?  Do you have a damper on your stove pipe?  If so, it might need to be adjusted specifically for your local conditions.  Otherwise, you could be shooting all of the hot air up the chimney.

What length of wood works best for each sauna stove?

16″ wood lengths for the small and medium sauna stoves. 21″ wood lengths for the large sauna stove.

Recommended Maintenance of a Kuuma Wood Burning Sauna Stove (Annual or as needed)

See (blog post here).

These few simple steps will help you protect, keep it looking nice, and extend the longevity of your KUUMA sauna stove for years or decades to come.

Can you load wood from outside the dressing room?

Yes, the 8″ or 12″ optional extensions are used to go through the wall.  We don’t recommend this because an outside feed adds about $1,000 to building construction costs, and you also lose 25% of the heat from the stove, so you need to upsize one stove size.  Almost all stove damage we’ve ever seen due to overheating has been because the draft isn’t properly managed, and the control isn’t in the hot room.  If you still want an outside feed, knowing this, we will be happy to build it for you.

**Inside versus Outside Feed Blog**

What are the Clearance Requirements (Meet UL standards for insurance)?

• • You always need a 48″ clearance in front of your stove.
  • Using a heat shield, you need a 7″ clearance on the side and 8″ clearance on the back from the shield on the stove to a non-combustible shield on the wall with a 1″ air gap behind it (PDF).
  • If you have heat shields on your sauna but not on the wall or vice versa, you need a 15.5″ clearance on the side and a 13.5″ clearance on the back (PDF).
  • Without heat shields or non-combustible surfaces, you need a 38″ clearance on the side and a 28″ clearance on the back (PDF).
  • A wall heat shield (non-combustible) needs to be 4″ off the floor and create a total height of 52″.  The width needs to extend past the sauna stove 8″ on each side.
  • If your ceiling is 8′ or less, a 3’x5′ heat shield on the ceiling with a 2″ air gap above it is required (PDF)—Law of Loyly (Bench Height).
  • Clearances to the edge of the non-combustible floor (PDF).

Do Kuuma wood-fired sauna stoves require a UL-rated or insulated hearth?

Hearth requirement: A non-combustible ember-protective surface only. No UL-rated or insulated hearth is required.

Sauna Building Tips:

Being in the sauna business, we often get many questions about building a sauna.

First Recommendation:

Spend a lot of time on Saunatimes.com, created by Glenn Auerbach.  He has done more research than anyone we know, and you can find nearly any information needed. He also has a great ebook for $25 that has helped hundreds of people build a kickass sauna!

General Recommendations:

• • People typically make the top bench too wide.  We recommend 20-21″.  More than that is uncomfortable to sit on.
  • The second bench is primarily for resting your feet or for sitting on. Again, please don’t install it too low.  If it’s too low, it tends to cut off circulation in the legs for shorter people.  It should be approximately 12″ below the top bench.
  • Ceiling height minimum of 8′.  This avoids needing a ceiling heat shield (ugly)—Law of Loyly (Bench Height). 
  • 1 or 2 steps to get on the second bench.  They should be fixed and not movable.
  • Attach a handrail to the wall next to the steps to assist with safety when getting on or off the benches
  • Ventilation Blog Post