Green Building Materials
At Mason’s Mill & Lumber Co., green building materials aren’t a side category — they’re a core part of how we help architects, builders, designers, and homeowners spec real wood and wood-alternative products that hold up outdoors, indoors, and everywhere in between. Our green catalog includes FSC®-certified sustainably sourced lumber, modified wood from Accoya®, Kebony®, and Thermory®. Every product is chosen for the same reason: it lasts, it’s honest about how it’s made, and it lets you build responsibly without giving up performance or looks.
What Counts as a "Green" Building Material?
A green building material is one that reduces environmental impact across its full life — how it’s harvested or manufactured, how long it performs, and what happens to it at end of life. The products on this page qualify in one or more of these ways:
Sustainably sourced. FSC®-certified or grown in well-managed forests where new trees replace what’s cut.
Chemically clean. Free from phenol, formaldehyde, and harmful VOCs — safe for interior and exterior use.
Modified for longevity. Thermal or bio-based modification extends service life to 25–50 years, so boards are replaced less often.
Tree-free or upcycled. Products like ACRE™ are made from agricultural byproducts that would otherwise be discarded.
LEED and Living Building Challenge eligible. FSC®-certified wood contributes to green building rating systems including LEED v4.1, LEED v5, and BREEAM.
If you’re speccing to hit a sustainability target — a LEED credit, a client mandate, or your own build standard — we can help you match the right material to the requirement.
Browse Our Green Building Materials
Thermory Benchmark Ash — Cutek Extreme Clear Finish
Thermory Benchmark Ash is the flagship hardwood product in Thermory's cladding and decking lineup — a thermally modified White Ash that sets the benchmark for what modified domestic hardwoods can achieve in exterior applications. Sourced responsibly from naturally renewing North American and Northern European forests, the ash is transformed through Thermory's proprietary "Intense" thermal modification process at 215°C (419°F) using only heat and steam. No chemicals, plastics, or additives are introduced at any stage — the transformation is purely physical, altering the wood's cell structure to permanently eliminate the food source for fungi and insects while dramatically reducing the board's ability to absorb moisture.
The result is a stunningly beautiful hardwood with an exotic, deep chocolate-brown color that runs consistently through the entire board — not a surface stain that can chip or wear away. Because the color is produced by molecular caramelization during modification, whenever the board is milled, cut, or sanded, the same rich brown tone remains visible. Thermory Benchmark Ash carries Durability Class 1 ratings under EN 350 — the highest possible durability class — with proven rot resistance for 25+ years in exterior applications, placing it in the same durability tier as tropical hardwoods like teak and ipe, but sourced sustainably from managed North American and European forests.
The performance advantages are substantial: equilibrium moisture content drops to just 4–7% (versus 18–22% for untreated ash), radial and tangential swelling are cut to under 3%, and Janka hardness measures approximately 4,450 N. Because the wood is naturally hydrophobic post-modification, it twists, cups, and bends significantly less than untreated hardwood — critical for the tight, gap-free seams demanded by modern architectural cladding profiles.
Each board is finished with Cutek Extreme Clear, a penetrating oil engineered to stabilize exterior wood from the inside out. Rather than forming a surface film like paint or varnish, Cutek carries its oils deep into the wood fibers, where they work continuously to slow moisture movement — the primary cause of cupping, checking, and end-splitting. Because the finish penetrates rather than coats, it cannot peel or flake, and maintenance requires no sanding or stripping — just clean the surface and reapply when it looks dry. The clear formulation adds no pigment, allowing the Benchmark Ash's rich chocolate-brown tone to show through initially before gradually silvering to a soft gray patina if left unmaintained with a colortone.
Ideal for premium architectural siding, cladding, soffits, porch ceilings, feature walls, decking, and porch flooring where the aesthetic warmth of exotic hardwood is desired alongside the sustainability and performance credentials of a domestically modified species.
Specifications
| Spec | Detail |
|---|---|
| Species | White Ash (Fraxinus americana / Fraxinus spp.) — thermally modified |
| Product Line | Thermory Benchmark Ash |
| Modification Level | Intense — 215°C (419°F) thermal modification, heat and steam only |
| Origin | North America and Northern Europe (sustainably managed forests) |
| Finish | Cutek Extreme Clear (penetrating oil) |
| Finish Type | Oil-based, non-film-forming |
| Color | Rich, exotic chocolate brown; consistent through full board thickness |
| Weathering | Silvers to gray patina over time if not maintained with colortone |
| Durability Class | Class 1 ("very durable") per EN 350 — highest possible rating |
| Use Class | 3.2 — exterior, above ground, exposed to prolonged wetting conditions (EN 335) |
| Fire Rating | D-s1, d0 (EN 13501-1); Class B flame spread achievable per ASTM E84 |
| Janka Hardness | 4,450 N (~1,000 lbf) |
| Brinell Hardness | 35.6 N/mm² |
| Bending Strength (MOR) | 58.6 N/mm² |
| Modulus of Elasticity | 15,535 N/mm² |
| Compressive Strength | 80 N/mm² |
| Oven-Dry Density | 581 kg/m³ |
| Initial Moisture Content | 6.7% ± 2% |
| Equilibrium Moisture Content | 4% at RH 35%; 6.6% at RH 60%; 10.9% at RH 90% |
| Radial Swelling (35→90% RH) | 0.9% → 2.9% |
| Tangential Swelling (35→90% RH) | 1.6% → 3.3% |
| Screw Traction Resistance | 29.9 N/mm² |
| Grade | Select |
| Warranty | 25+ years rot resistance (Thermory) |
| Standard Lengths | 0.8 – 3.9 m (cladding); 0.8 – 3.9+ m (decking) |
| Applications | Premium exterior siding, cladding, soffits, porch ceilings, feature walls, decking, porch flooring, architectural millwork |
| Fixings | Stainless steel required (FG Screws or PaCS Clad clips recommended); pre-drilling advised |
| Maintenance | Clean and re-oil with Cutek Extreme as needed — no sanding or stripping required |
| Sustainability | Chemical-free modification; sustainable alternative to tropical hardwoods; sourced from managed forests |
| Environmental | EPD available; GWP-Biogenic A1-A3: -5.66E1 kg CO₂e/m³ (net-negative embodied carbon) |
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Our Green Product Lines
Mason’s Mill stocks the three leading names in modified wood — Accoya®, Kebony®, and Thermory® — each engineered to outlast traditional lumber without the chemicals of pressure-treated pine or the environmental cost of tropical hardwoods. Accoya® starts with fast-growing, FSC®-certified Radiata Pine and puts it through a non-toxic acetylation process that permanently changes the wood at the cell level, delivering a Class 1 durable board backed by a 50-year above-ground warranty (25 years in ground or freshwater) — ideal for cladding, decking, siding, windows, and doors. Kebony® permanently modifies sustainably sourced softwood using furfuryl alcohol, a bio-based liquid made from agricultural crop waste, producing boards with the hardness and stability of tropical hardwoods and a 30-year warranty on Character and Clear grades. Thermory® uses only heat and steam — no chemicals — to reduce moisture and rearrange the cell structure, yielding boards 7x less likely to move than untreated wood; Mason’s Mill operates the Thermory USA Central Warehouse in Houston and holds the largest Thermory® inventory in the country across decking, cladding, siding, flooring, slatwall, and rough lumber.
Beyond these three brands, Mason’s Mill sources FSC®-certified rough lumber and millwork across a range of species for custom milling, moulding, cabinetry, and specialty projects. FSC® Chain-of-Custody tracks every board from forest to job site, giving architects and builders the documentation they need for LEED, BREEAM, and Living Building Challenge submissions.
Why Green Building Materials Matter
Green materials aren’t just a marketing angle anymore — they’re a spec requirement on a growing share of commercial and residential projects. Reasons architects, builders, and owners are choosing sustainable materials right now:
LEED v5 MRc4 now uses a Multi-Attribute Scoring methodology that ranks FSC®-certified building products the highest of any wood certification.
BREEAM 2018 and LEED v4.1 both reward third-party-verified EPDs, LCAs, and FSC® Chain-of-Custody documentation.
Modified wood products cut lifecycle impact because boards last 2–3x longer than untreated softwood — fewer replacements, less waste, less carbon over the life of the building.
Tree-free composites like ACRE™ divert agricultural waste from landfills and remove tropical hardwood pressure from the supply chain.
Chemical-free processes (thermal modification, acetylation, furfurylation) produce boards that are safe to handle, non-toxic to install, and safe to dispose of.
For homeowners, the payoff is a home that holds its finish for decades with minimal upkeep. For architects and builders, it’s a documented, defensible path to hitting sustainability targets on the drawing.
Frequently Asked Questions
It depends on the project. Accoya® has the longest above-ground warranty (50 years) and starts with FSC®-certified Radiata Pine. Kebony® uses bio-based furfuryl alcohol derived from agricultural crop waste. Thermory® is completely chemical-free, modified using only heat and steam. All three are strong sustainable choices — we're happy to help you pick the right one based on species, application, budget, and the look you're after.
Modified wood is real wood that has been permanently altered — either chemically (Accoya®, Kebony®) or thermally (Thermory®) — to resist rot, warping, and insects without the toxic preservatives found in pressure-treated lumber. It's considered a green building material because it starts with sustainably sourced or FSC®-certified species, uses non-toxic processes, and lasts 2–3x longer than untreated softwood — meaning fewer replacements, less waste, and a lower lifetime carbon footprint.
No. Pressure-treated lumber uses chemical preservatives forced into the wood under pressure. Thermally modified wood — like Thermory® — uses only heat and steam, with no chemicals added. The process reduces moisture to near zero and rearranges the wood's cell structure so it naturally resists rot, warping, and insects. Safer to handle, safer to install, and safer to dispose of at end of life.
Yes. FSC®-certified wood contributes to LEED v4.1 and LEED v5 credits — including the new MRc4 Multi-Attribute Scoring in v5, where FSC® ranks the highest of any wood certification. Modified wood from Accoya®, Kebony®, and Thermory® with published EPDs also contributes to LEED and BREEAM credits, as well as Living Building Challenge submissions. Ask us for the current documentation on any product you're speccing.
Accoya® carries a 50-year warranty above ground and 25 years in ground or freshwater. Kebony® carries a 30-year warranty on Character and Clear grades. Thermory® decking and cladding carry a 25+ year rot-resistance warranty. In real-world use, service life often exceeds the warranty period — especially on properly detailed exterior installations.
All three are modified wood, but the process is different. Accoya® uses acetylation — a non-toxic chemical process — on FSC®-certified Radiata Pine, delivering the longest warranty and best dimensional stability. Kebony® uses furfurylation — a bio-based process using agricultural waste — on sustainably sourced softwood to mimic the hardness of tropical hardwoods. Thermory® uses only heat and steam — no chemicals at all — on species like Ash, Pine, and Spruce. Different processes, different price points, different aesthetics — all excellent green options.
Yes. Nearly every product on this page has a $10 sample available through our Sample Shop, and the sample cost is credited back on your full order. It's the easiest way to see, touch, and finish-test the material before you spec it.
Yes. Accoya®, Kebony®, and Thermory® are all non-toxic and safe for indoor applications. Thermory® is a popular choice for interior flooring, slatwall, and biophilic-design feature walls. Accoya® is used for windows, doors, and interior millwork. Kebony® is used for flooring and interior cladding. None off-gas harmful VOCs.