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About

About the planner

A sauna is a small building with a few hard rules. We wrote those rules into an engine, sourced every one, and priced the build from real store listings.

Last updated October 9, 2026

  • Rules from heater makersBench heights, room volume, vents and insulation come from Harvia and HUUM manuals and product data.
  • Prices with a dateEvery priced line names the store and the day it was read.
  • Run by Westernmost LLCA small product studio in Sheridan, Wyoming.

How the planner works

  1. Benches. The top bench sits 46 in under the ceiling, inside HUUM's 1100 to 1300 mm band. A lower tier steps 18 in down (our default). Seats are counted at 24 in each, Harvia's 60 cm.
  2. Heater. Room volume, plus 1.2 m3 for each m2 of glass (Harvia's rule), has to sit inside the maker's rated range. We pick the smallest model that covers it and list others that also fit.
  3. Air. An adjustable intake low by the heater, an exhaust with twice the area low on the opposite wall, and a drying vent high on that wall, as HUUM's manual lays out for gravity ventilation.
  4. Envelope. Mineral wool, a continuous foil vapor barrier with taped seams, a 3/4 in furring gap, then the boards, 4 in off the floor.
  5. Framing and shell. Studs at 16 in, ceiling joists at 16 in; outdoors, 2x6 walls on a skid floor over deck blocks with a 4/12 metal roof.
  6. Prices. Lumber, sheet goods and fasteners come from Home Depot and Lowe's listings read on October 8, 2026 (and September 30 for a few lines); sauna parts from Haven of Heat, The Sauna Heater, Twin Creeks Log Home Supply and Superarbor, read October 9, 2026. On October 9, Home Depot and Lowe's refused automated reads, so we did not refresh those lines that day.

What it does not do

It does not approve wiring, stove clearances or structures. Where a heater or stove manual differs from the planner, the manual wins. An electric heater is connected by a licensed electrician, and most towns want a permit for a new 240 V circuit and for an outdoor building.

Who we are

The Sauna Planner is a Westernmost LLC site, 32 N Gould St, Sheridan, WY 82801, USA. Write to hello@thesaunaplanner.com.

Sources

Every rule the planner applies comes from the heater maker's own manual or product data where one exists. Where a number is our own default, the designer says so next to it.

  1. 01HUUMDROP 2.0 electric heater user manual (EU, v6)Room 2000 to 2300 mm high, never under 1900 mm; top bench 1100 to 1300 mm below the ceiling; 50 to 100 mm insulation, foil with taped joints, 10 mm gap behind the boards, 12 to 16 mm boards, 100 mm from the floor; supply air 50 to 100 mm at or below heater mid-height (400 mm), exhaust twice that on the opposite wall at least 200 mm higher (600 mm), drying vent under the ceiling; six air changes an hour; only a certified electrician connects the heater.Read 2026-10-09
  2. 02HarviaHow do I select the correct heater power?Each square meter of stone, glass or similar uninsulated surface adds as much load as 1.2 cubic meters of room volume.Read 2026-10-09 (search listing; the page answered 403)
  3. 03HarviaKIP45 product dataRoom 106 to 212 cu ft, minimum room height 6.56 ft, 3.61 ft from the heater to the ceiling.Read 2026-10-09
  4. 04HarviaM3 wood-burning heater product dataRoom 212 to 459 cu ft; to combustible material 11.81 in front and rear, 9.84 in each side; minimum room height 6.56 ft.Read 2026-10-09
  5. 05HarviaPro 20 wood-burning heater product data300 mm (11.81 in) to combustible material front, rear and sides; 1.3 m to the ceiling; minimum room height 2 m.Read 2026-10-09 (search listing)
  6. 06HarviaHow to design a saunaThe seat for one person is usually 60 cm wide.Read 2026-10-09
  7. 07Haven of HeatHeater listings with the maker's room rangesHarvia KIP 4.5 kW 100 to 210 cu ft, 6 kW 170 to 300, 8 kW 250 to 425; Cilindro 9 kW 141 to 494; Harvia M3 212 to 459; Pro 20 283 to 706.Read 2026-10-09
  8. 08NFPA 70, National Electrical CodeArticle 424.4(B), branch-circuit sizing for fixed electric space-heating equipment (2020 text)Branch-circuit conductors are sized at no less than 125 percent of the load. Your jurisdiction's adopted edition and the heater's nameplate govern.Read 2026-10-09 (secondary summary)