WINTHERWAX · Project

Cost-Effective Wooden Passive Windows That Last 25+ Years Without Toxic Coatings

constructionPilotedTRL 7

Imagine a window frame made from regular spruce wood that's been heat-treated and coated with a special wax — no toxic chemicals involved — so it can survive outdoors for over 25 years without rotting. Two Slovenian SMEs figured out how to make a passive window this way that insulates almost as well as a wall, all for about €369 per unit. The wax coating is translucent, so the wood keeps its natural look instead of being hidden under thick paint or varnish. It's basically a premium energy-efficient window at a budget price point.

By the numbers

€369

Target retail price per window unit

0.09 W/m²K

Thermal transmittance

25+ years

Durability at Class 1 (fully exposed to environment)

4.1%

Target EU wooden passive window market share

€1,295,080

EU funding received

SME partners in consortium

The business problem

What needed solving

Wooden windows are seen as expensive and high-maintenance compared to PVC, yet PVC lacks the sustainability and aesthetic appeal that eco-conscious builders want. Current wood preservation methods rely on chemical biocides that face increasing regulatory pressure across the EU. Builders need a cost-competitive, long-lasting, chemical-free wooden window that meets passive house energy standards.

The solution

What was built

A definitive prototype of a passive window made from thermally modified Norway spruce with a biocide-free wax coating. The final deliverable included complete technical specifications for a window achieving 0.09 W/m²K thermal transmittance at a target price of €369.

Audience

Who needs this

Wood window manufacturers competing against PVC on pricePassive house builders and certified installersProperty developers targeting near-zero-energy building standardsWood coating and preservation companies seeking biocide-free alternativesBuilding material distributors in Nordic and Central European markets

Business applications

Who can put this to work

Window and door manufacturing

SME

Target: Wood window manufacturers looking to compete with PVC on price while staying eco-friendly

If you are a wood window manufacturer losing market share to cheap PVC alternatives — this project developed a thermally modified spruce window with a biocide-free wax coating that reaches passive-house-level insulation (0.09 W/m²K) at a target price of €369. That price point undercuts most wooden passive windows on the market while offering Class 1 durability of more than 25 years.

Construction and real estate development

mid-size

Target: Residential developers building energy-efficient or passive houses

If you are a property developer required to meet near-zero-energy building standards — this project created a wooden passive window with thermal transmittance of 0.09 W/m²K, helping buildings meet passive house certification. The biocide-free coating and natural wood look add selling points for environmentally conscious buyers, while the €369 price keeps construction budgets manageable.

Wood treatment and preservation

SME

Target: Companies specializing in wood coatings, preservatives, or thermal modification technologies

If you are a wood treatment company seeking alternatives to chemical preservatives under tightening EU biocide regulations — this project used a patented SILVAPRO thermal modification process combined with a biocide-free wax that prevents cracking and decay for more than 25 years. Licensing this technology could open a new product line for exterior wood applications beyond windows.

Frequently asked

Quick answers

What does this window cost compared to competitors?

The project targeted a retail price of €369 per window unit, which they claim beats competitor pricing in the wooden passive window segment. This positions it as a cost-effective alternative for builders who want wood performance without premium wood pricing.

Can this be manufactured at industrial scale?

The project was funded under SME Instrument Phase 2, which specifically supports scaling up close-to-market innovations. The consortium includes two industry partners — M SORA (a window manufacturer) and SILVAPRODUKT (a wood preservation specialist) — both already operating in production environments. The final deliverable was a definitive prototype ready for commercialization.

What about intellectual property and licensing?

The thermal modification process uses the patented SILVAPRO technology owned by SILVAPRODUKT. Any company interested in using this specific wood treatment and wax coating combination would need to negotiate licensing terms with the consortium partners in Slovenia.

How does it meet EU energy efficiency regulations?

With a thermal transmittance of 0.09 W/m²K, this window exceeds passive house requirements. This makes it directly relevant for compliance with the EU Energy Performance of Buildings Directive and near-zero-energy building standards taking effect across member states.

How long does the coating last before maintenance is needed?

The project claims Class 1 durability — more than 25 years fully exposed to the environment. The biocide-free wax reduces cracking, which is identified as the main cause of wood decay. Based on available project data, specific maintenance intervals were not detailed.

Is this compatible with existing window installation methods?

Based on available project data, the WINTHERWAX window is a passive window made from Norway spruce, which follows standard wooden window construction. No special installation procedures were mentioned, suggesting compatibility with conventional window fitting processes.

Consortium

Who built it

This is a lean, all-industry consortium of 2 Slovenian SMEs with no universities or research organizations — a clear signal this is about commercialization, not basic research. M SORA handles window manufacturing and SILVAPRODUKT brings the patented SILVAPRO wood treatment process. The 100% industry ratio and SME Instrument Phase 2 funding (€1,295,080) confirm this was a market-driven scale-up effort. The single-country setup in Slovenia keeps coordination simple but may limit initial distribution networks across the EU. A business partner or distributor in larger EU markets (Germany, France, Scandinavia) could accelerate market entry significantly.

M SORA TRGOVINA IN PROIZVODNJA DDCoordinator · SI

How to reach the team

M SORA is a Slovenian window manufacturer — their commercial team can be reached through their company website or via SciTransfer introduction.

Order a report on this consortium See M SORA TRGOVINA IN PROIZVODNJA DD profile →

Next steps

Talk to the team behind this work.

Want an introduction to the WINTHERWAX team for licensing, distribution, or supply partnership? Contact SciTransfer — we connect businesses with EU research results.

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