The thermo-aspen blog
Thermo-aspen sauna guides
How to choose, size, build, and care for a thermo-aspen sauna, with every number traced to the page it came from.
Material science
Does Thermo-Aspen Off-Gas in a Sauna? What the VOC Tests Found
Thermory says its sauna materials are modified with only heat and steam, without added chemicals. In VTT tests on pine, thermally modified wood gave off about 44 to 84% less total VOC than unmodified pine.
Read the articleThermo-Aspen vs Plain Aspen: What Do Heat and Steam Change?
Thermal modification uses heat and steam to permanently change the wood’s color and how it takes up moisture. It stays aspen: soft, smooth, and fine-grained.
Read the articleWhy Thermo-Aspen Sauna Benches Stay Comfortable to Sit On
A thermo-aspen bench warms up with the room, but wood takes up heat far more slowly than metal or stone, so it does not feel extremely hot. The ThermoWood® Handbook reports 20 to 25% lower conductivity for thermally modified Nordic softwood.
Read the articleSpecifying
Building a Sauna? 12 Numbers From the 2026 ThermoWood® Handbook
What the International ThermoWood Association’s handbook says about sauna walls, ceilings, and benches: 12 numbers in US units, from air gap to fasteners.
Read the articleBuilding With Thermo-Aspen: 7 Things to Plan For
Thermo-aspen suits sauna walls, ceilings, and benches. Seven things to plan for when you build with it, from framing and fasteners to fire code and exterior finish.
Read the articleThermo-S vs Thermo-D: What the ThermoWood® Classes Mean for Saunas
Both ThermoWood® classes are recommended for sauna walls, ceilings, and benches. They differ in modification temperature, color, stability, and outdoor use.
Read the articleBuilding
How to Frame Sauna Paneling: Battens, Air Gap, Thickness
Fix sauna panels to battens no more than 23-1/2 in apart, over a ventilated gap at least 13/16 in deep. A 1x furring strip is 3/4 in thick, so it falls just short.
Read the articleHow to Store, Cut, and Sand Thermo-Aspen: A Shop Guide
Keep the bundles closed, flat, and indoors, give the boards days to weeks in the room, and cut with fine teeth under dust extraction. Planed boards rarely need sanding.
Read the articleWhat Fasteners Does Thermo-Aspen Sauna Paneling Need?
Stainless steel for every clip, staple, nail, and screw, fixed the way the board’s maker says. Thermory’s guide covers its panels. For ThermoWood® products, the handbook sets Type 304 as the minimum and Type 316 as the acid-resistant step up.
Read the articleCare
Can Mold Grow in a Sauna? How to Keep It Dry and Clean
A sauna stays dry and clean when it airs out after every session. The venting and cleaning routine, and what to do if spots appear.
Read the articleHow to Finish Thermo-Aspen Sauna Benches: Wax, Oil, and Care
Use the sauna wax or breathable protector your board’s maker names. Thermory recommends waxing its sauna wood and oiling its unfinished PLATE bench board; the ThermoWood® Handbook recommends mineral oil and rules out linseed oil.
Read the articlePrefer the reference pages?