HOLZ100 TECHNOLOGY
A revolutionary solid wood construction system by Erwin Thoma — built entirely from massive timber boards joined by hardwood dowels. Zero glue. Zero nails. Zero toxic chemistry. A building that breathes.
Founded by Austrian forest scientist and philosopher Erwin Thoma in the alpine valleys of Carinthia, Holz100 is not simply a building material — it is a paradigm. The name means exactly what it states: 100% wood.
Every wall, floor, and ceiling panel consists of solid, massive timber boards — not laminated, not glued, not chemically treated. The boards are mechanically interlocked using hardwood dowels that expand with natural moisture, creating a monolithic wood structure of extraordinary rigidity and longevity.
There are no metal nails, no synthetic adhesives, no vapor barriers, no foam insulation. The result is a building that functions as a living organism — breathing, regulating, and enduring for centuries.
Erwin Thoma's alpine forest science since the 1990s.
Pure mechanical joints — no glue, no nails, no metal.
No toxic compounds in any component of the structure.
Every element of the system works together as a single living material.
Holz100 walls are not framed or insulated with synthetic materials. They are composed entirely of massive solid timber boards — typically 30 to 40 centimetres thick — stacked and cross-bonded to form a monolithic panel. This single-material approach eliminates the thermal bridges and moisture traps that plague conventional layered wall assemblies.
Boards are held together exclusively by hardwood dowels driven dry into precisely drilled channels. As the dowel absorbs ambient moisture it swells, creating a self-tightening joint that strengthens over time. No adhesive, no metal fastener, no chemical bonding agent is used anywhere in the structure. The system is entirely reversible and fully recyclable at end of life.
Timber used in Holz100 is harvested exclusively in winter, during the waning moon phase. At this time sap retreats deep into the root system, leaving the wood fibres drier, denser, and significantly more resistant to rot, insects, and mould. This traditional practice — validated by modern forest science — produces timber that requires no chemical preservatives and demonstrates measurably superior durability over centuries.
All timber in the Holz100 system is sourced from FSC and PEFC certified forests, ensuring legal, traceable, and ecologically managed supply chains. Each cubic metre of wood permanently sequesters approximately one tonne of CO₂ — meaning a Holz100 home is, by definition, a carbon-negative structure. The forest gives; the building keeps.
The sheer mass of a 40 cm solid wood wall creates extraordinary thermal inertia. The structure absorbs heat slowly throughout the day and releases it gently through the night — a passive heating and cooling cycle that requires no mechanical intervention.
Daily temperature swing inside a Holz100 home, even through extreme seasonal shifts. The walls act as a thermal battery.
Typical daily temperature swing inside a conventional lightweight-frame or masonry home — requiring constant active heating or cooling.
In practice: Holz100 homes stay warm in winter without a running heating system for days after the fire goes out. In summer, the walls absorb midday heat and prevent it from reaching the interior — maintaining coolness without air conditioning.
Solid wood is a hygroscopic material — it naturally absorbs and releases moisture in response to the air around it. A Holz100 wall acts as a passive humidity regulator, maintaining indoor relative humidity between 45 and 60% RH without mechanical ventilation or vapour barriers.
This is the range in which human respiratory systems, immune function, and sleep quality are optimised. Viruses and bacteria struggle to survive. Dust mites are suppressed. The building breathes so you breathe better.
Additionally, solid wood is one of the few building materials that reduces indoor radon concentration. Holz100 homes measure 3–4 times lower radon levels than equivalent conventional buildings — a significant factor for long-term occupant health.
Conventional construction requires synthetic vapour barriers to manage moisture migration. Holz100 eliminates the need entirely — wood manages moisture without assistance.
Naturally maintained without humidifiers or dehumidifiers. The walls adapt to seasonal variation, occupancy levels, and outdoor conditions autonomously.
Wood does not off-gas radon and actively adsorbs it. Research from the Thoma Institute confirms significantly reduced indoor radon versus masonry and concrete structures.
Medieval timber structures built without modern chemistry still stand across Europe. Holz100 is engineered to the same standard.
The oldest surviving timber structures in Europe are over 800 years old. They were built without glue, without metal fasteners, without chemical preservatives — using the same principles that underpin Holz100 today. Moon-harvested timber, dense and dry, connected by wooden pegs, has proven its durability across centuries of harsh alpine climates.
Holz100 is engineered with a design life exceeding 200 years. Unlike conventional buildings that require costly maintenance, chemical retreatments, and eventual replacement of synthetic components, a Holz100 structure improves with age. The wood compresses and tightens. The dowels become immovable. The building grows stronger.
And unlike a conventional property that depreciates structurally over decades, a Holz100 home is an appreciating asset — both financially and ecologically.
Holz100 is not marketed as a health product. It simply does not contain the compounds that make conventional buildings harmful.
Volatile organic compounds — solvents, formaldehyde, benzene, toluene — off-gas from paints, adhesives, pressed wood products, and insulation foams in conventional buildings for years after construction. Holz100 contains none of these materials. There is nothing to off-gas.
No pressed wood products, no OSB, no MDF, no plywood — the primary sources of formaldehyde in modern homes. Holz100 uses only solid, unmilled timber. The absence of formaldehyde is structurally guaranteed, not dependent on product certification that can vary.
Solid wood naturally dampens electromagnetic fields and produces negative ions — both associated with improved sleep quality and reduced cortisol levels. Occupants of Holz100 buildings consistently report improved sleep within the first weeks of moving in. Research from the University of Graz supports these findings.
The combination of controlled humidity, zero off-gassing, and reduced dust mite habitat makes Holz100 environments particularly beneficial for people with respiratory conditions, allergies, and chemical sensitivities. Medical practitioners in German-speaking countries actively recommend Holz100 homes for patients with MCS.
Independent research conducted by the Thoma Institute measured indoor air quality in Holz100 structures against matched conventional buildings. The results showed consistently three times better composite air quality scores, driven by the absence of chemical compounds and the active regulation of humidity and particulate levels.
Wood is the material of our evolutionary environment. Studies in environmental psychology confirm that living and working among natural wood surfaces reduces stress hormones, lowers blood pressure, and improves cognitive function. Holz100 brings the measurable effects of forest immersion indoors.
"Nature does not build with glue. Neither should we."
— Erwin Thoma, founder of Holz100
Every claim about Holz100 is backed by third-party certification, not marketing copy.
Purewood is a licensed member of the international Erwin Thoma partner network — a curated group of builders across 30+ countries bound by strict construction standards and ongoing training. Membership requires demonstrated adherence to the full Holz100 methodology, including material sourcing, harvesting calendar, and assembly protocols.
Holz100 building components carry Cradle-to-Cradle Gold certification — one of the most rigorous material health and circularity standards in the world. This certification verifies that every material can be safely returned to biological or technical cycles at end of life without contamination or waste.
All timber is sourced exclusively from FSC and PEFC certified forests — the global benchmarks for responsible forest management. Certification covers traceability from forest floor to building site, ensuring no illegal logging, habitat destruction, or labour violations anywhere in the supply chain.
Reading about Holz100 gives you knowledge. Touching the walls, sleeping inside them, and measuring the air yourself gives you certainty. The Purewood Beskidy showroom is a fully functioning Holz100 home — open for guided visits by appointment.