What are the key benefits of thermally modified wood?
Posted: May 25, 2026Author – Ryan Palma Owner/CEO Sustainable Lumber Co.
After a year of research and development, we have officially launched our new line of thermally modified wood siding Montanafied! Currently available in unfinished 1×6 and 1×8 T&G smooth and wire brushed texture. We will have prefinished options available soon. Call or email us for more information and pricing, info @ sustainablelumberco.com or (406) 642-7120
What is thermally modified wood and what are the benefits?
If you’re searching for an exterior siding that delivers the timeless beauty of real wood while standing up to harsh weather, moisture, and time; you may have just found it. Thermally modified wood is a low/no maintenance wood siding with no toxic chemicals, it is quickly becoming a top choice for environmentally conscious buyers.
Thermally modified wood is real wood that goes through a chemical free process using high heat and steam in a low oxygen environment. This permanently alters the wood’s cellular structure by breaking down hemicelluloses, making it far more stable, durable, and resistant to the elements while keeping it 100% natural.
Here are the key benefits that make thermally modified wood siding an outstanding option for your home’s exterior:
- Superior Dimensional Stability
Thermally modified wood absorbs up to 50% less moisture than untreated wood. This translates to 40–80% less swelling, shrinking, warping, cupping, and movement with changes in humidity or temperature. For siding, that means tighter joints, fewer gaps, and a straighter, more attractive facade that holds up beautifully over decades.
- Excellent Water Resistance
Thermally modified wood is highly water resistant (hydrophobic). It absorbs 40–60%+ less moisture and reaches a much lower equilibrium moisture content. While it is not fully waterproof, it handles rain, snow, humidity, and freeze thaw cycles exceptionally well, staying drier and resisting water related damage far better than conventional wood siding.
Proper installation with good drainage, ventilation, and flashing maximizes this performance, making it ideal for exterior applications.
- Enhanced Durability & Decay Resistance
The heat treatment essentially removes (caramelizes) natural sugars and compounds that fungi, mold, and decay organisms feed on. As a result, thermally modified wood siding offers strong natural resistance to rot, brown rot, white rot, and soft rot. When installed correctly above ground, it can easily last 25–30+ years with minimal issues.
- Natural Pest Resistance
By eliminating the wood’s natural food source for insects, thermally modified siding naturally deters termites and other wood-boring pests, no added pesticides or chemicals required.
- Beautiful, Consistent Aesthetics
The process creates rich, warm chocolate brown tones that penetrate the entire board (not just the surface). This gives siding a premium, uniform look right from day one. Small scratches or cuts are far less noticeable, if left unfinished over time it can develop a lovely silvery gray patina, or you can maintain the rich color with occasional oiling.
- 100% Chemical-Free & Eco-Friendly
Unlike pressure treated lumber, no preservatives, copper compounds, or toxins are added. It’s non-toxic, safe for children, pets, and the environment, and fully biodegradable at the end of its long life span, one of the most sustainable eco-friendly siding choices available.
- Low Maintenance Lifestyle
Because it resists moisture, mold, decay, and insects so effectively, thermally modified wood siding requires far less upkeep than traditional wood. Many homeowners simply let it weather naturally, saving significant time and money on painting, staining, or replacements.
- Bonus Performance Perks
- Improved thermal insulation (up to ~20% better in some tests)
- Lighter weight, making it easier to handle and install
- Excellent performance for demanding exterior cladding and siding projects in humid and dry environments
Why Thermally Modified Wood Siding Shines in Challenging and Harsh Climates
If you live in an area with big temperature swings, heavy snow, rain, and freeze thaw cycles, such as Montana, thermally modified wood siding really stands out. Its dramatically reduced moisture absorption helps it resist the warping, cracking, and decay that commonly plague regular wood siding in variable climates like ours.
The bottom line: Thermally modified wood siding beautifully combines the natural warmth, character, and beauty of real wood with modern high performance traits. It offers superior water resistance, dimensional stability, durability, pest resistance, low maintenance, and eco-friendliness, all in one sustainable package.
Whether you’re building new, replacing old siding, or simply want an exterior that looks stunning and performs reliably for decades with minimal effort, thermally modified wood is an excellent choice.
Contact us for a quote
Our knowledgeable team at sustainable lumber is here to answer any additional questions you may have. Call us today for a free quote (406) 642-7120 or click here to submit an inquiry online. We look forward to helping you with your next project!