Introduction — What 'Sustainable' Really Means for Building Materials in 2026

The term 'sustainable' has been used inflationarily in the construction industry for years. In 2026, this is fundamentally changing: The EU Taxonomy Regulation, tightened DGNB criteria, and the mandatory disclosure of verified CO₂ footprints in public tenders from 2026 onwards are forcing the industry to provide measurable, standardized evidence. A building material is now considered sustainable only if it demonstrates measurably lower environmental impact than conventional alternatives over its entire life cycle — from raw material extraction through the use phase to deconstruction.

The central measurement metric is Global Warming Potential (GWP), expressed in kg CO₂ equivalents per functional unit (e.g., per m² wall area with U-value 0.24 W/m²K or per m³ concrete with compressive strength C30/37). Additional indicators include Ozone Depletion Potential (ODP), Acidification Potential (AP), Eutrophication Potential (EP), and cumulative Primary Energy Input (PEI). Since 2024, these values must be documented in Environmental Product Declarations (EPDs) according to EN 15804+A2 — a standard that Heidelberg Materials, Holcim, and other major manufacturers now meet for their core product lines.

The scope of analysis is critical: Cradle-to-Gate EPDs cover only manufacturing through factory gate, Cradle-to-Grave analyses cover the complete life cycle including disposal. The ideal case is Cradle-to-Cradle: the building material is completely returned to biological or technical cycles after its use phase, without quality loss — a principle that has finally arrived in structural construction in 2026.

Life Cycle Assessment (LCA) and EPD: What Building Owners Should Check in 2026

The environmental product declaration (Life Cycle Assessment, LCA) according to ISO 14040/14044 forms the scientific basis for every sustainability assessment. It is divided into phases A1-A3 (manufacturing), A4-A5 (construction), B1-B7 (use), C1-C4 (disposal), and D (recycling potential outside the system boundary). For building owners, three EPD types are relevant:

  • Product EPD: Manufacturer-specific, e.g., for autoclaved aerated concrete from Heidelberg Materials with GWP 194 kg CO₂eq/m³ (A1-A3)
  • Average EPD: Industry average, created by associations such as the German Calcium Silicate Brick Industry Association
  • Sectoral EPD: Simplified declaration for SMEs, accepted for DGNB Silver

Data quality is critical. EPDs according to EN 15804+A2 (valid since 2022) require site-specific data for at least 70% of production mass. Older EPDs according to EN 15804+A1 may no longer be used in DGNB projects from 2027 onwards. Verification points for building owners:

  1. Validity period (max. 5 years, earlier if significant process changes occur)
  2. Verification by independent third parties (Institut Bauen und Umwelt IBU, EPD International)
  3. System boundary: At least Cradle-to-Gate (A1-A3), preferably Cradle-to-Grave (including C modules)
  4. Declared unit vs. functional unit: 1 m³ concrete is not comparable to 1 m² insulation — the functional unit must reflect performance
  5. Biogenic carbon: For wood products, it must be stated whether temporary CO₂ storage (using the -1/+1 method) was accounted for

A concrete example: Holcim's recycled concrete RC-C25/30 shows a GWP of 287 kg CO₂eq/m³ in the EPD (A1-A3), conventional C25/30 is 312 kg CO₂eq/m³ — a reduction of 8%. However, the functional unit "foundation 10 m³, 50 years use" shows that longer transport distances (recycled aggregate from urban extraction regions) partially offset the advantage in the A4 phase. Only the complete view A1-A5 reveals the true advantage: 3,120 vs. 3,380 kg CO₂eq/10 m³.

Cradle-to-Cradle-Certified Building Materials in DACH 2026

The Cradle-to-Cradle Certified® program from the C2C Products Innovation Institute evaluates products in five categories: Material Health, Circular Design, Renewable Energy & Climate, Water Stewardship, and Social Fairness. Certification levels are Basic, Bronze, Silver, Gold, and Platinum. In the construction sector, the following product groups achieved C2C certificates in 2026:

Waterproofing Membranes: Sika has renewed the Silver certification for the hybrid plastic waterproofing membrane Sarnafil AT. The membrane consists of fully declared polymers without PVC, is mechanically separable, and 100% recyclable into technical cycles. GWP: 4.2 kg CO₂eq/m² (including pro-rata compensation of production energy).

Timber Construction Systems: Baufritz received Gold certification in 2026 for its HOIZ wall system. The multi-layer timber frame construction uses exclusively sawn timber from PEFC-certified forests (radius max. 150 km), adhesive and formaldehyde-free wood fiber insulation from Steico, and mineral surface coatings. Every connection is mechanically detachable, material purity reaches 97%. Biogenic CO₂ storage is calculated using the -1/+1 method: -89 kg CO₂eq/m² wall area over 80 years of use.

Insulation Materials: Rockwool offers stone wool insulation boards with Bronze certification. The challenge is material health: phenolic resin-based binders are fully declared but not recyclable. However, the boards can be 100% recycled — Rockwool accepts offcuts and demolition material, melts it down, and produces new insulation boards with identical λ values (0.035 W/mK).

Coatings: Keim Farben achieved Silver level for mineral silicate paints. The products contain no VOCs (Volatile Organic Compounds), are vapor-permeable, and biologically degradable or recyclable as mineral construction waste after use.

Important caveat: C2C certificates evaluate the product, not the entire building. A C2C Gold wall system can show a worse overall balance in an inefficient building with high heating energy demand than conventional construction with Passive House standard. DGNB awards bonus points for C2C-certified materials at Silver level and above in criterion ENV1.1 (Environmental Product Declaration), maximum 3 of 100 total points.

Recycled Concrete and RC Building Materials: Status 2026

Recycled aggregates (RC) from demolition material are permitted in Germany according to DIN EN 12620 and the DAfStb guideline "Concrete according to DIN EN 206-1 and DIN 1045-2 with recycled aggregates according to DIN EN 12620" (2010, revised 2023) up to 45% substitution rate in structural concrete — for RC Type 2 (processed concrete rubble, grain size 4/32) even up to 100% for exposure classes XC1-XC4 and XF1.

Market share in 2026 is approximately 8% in building construction (DACH average), concentrated in urban regions with high demolition density. Heidelberg Materials operates its own RC processing plants in Berlin, Munich, and Vienna with annual capacity of 420,000 tons. Quality control includes:

  • Chloride content < 0.020 wt.% (DIN EN 206-1) to prevent reinforcement corrosion
  • Water absorption < 10% (DIN EN 12620) through pre-screening of porous fractions
  • Grain bulk density > 2000 kg/m³ (exclusion of aerated concrete, gypsum residues)
  • Sulfate content < 0.8 wt.% to prevent expansion

The mechanical properties of RC concrete are slightly below primary concrete: compressive strength C25/30 at concrete age 28 d: RC concrete 32.1 N/mm² (n=50), primary concrete 34.8 N/mm² — a difference of 8%, which can be compensated by slight increase in cement dosage (15 kg/m³). The elastic modulus decreases by approximately 10% (from 31,000 to 28,000 N/mm²), which is unproblematic for statically low-stress components (floor slabs, foundations).

The CO₂ balance is complex: savings from avoided primary raw materials (approx. 8 kg CO₂eq/ton aggregate) are offset by energy-intensive processing (crushing, screening, magnetic separation). Net savings according to Holcim's EPD: 25 kg CO₂eq/m³ concrete (8% reduction) at 45% RC content. At 100% RC content, savings increase to only 18%, as higher cement demand partially offsets the advantage.

Legal framework: The Substitute Materials Regulation (ErsatzbaustoffV, valid since August 1, 2023) defines RC building materials Class RC-1 as unrestricted use, RC-2 and RC-3 subject to installation restrictions depending on groundwater protection priority. Additionally, the Circular Economy Act (KrWG §17) requires a minimum substitution rate of 10% in public construction projects over EUR 5 million starting in 2025 — a driver for market penetration.

Hemp, Straw, Clay: Renewable Building Materials in Practical Use

Renewable raw materials (NawaRo) offer negative global warming potential in the manufacturing phase through CO₂ storage during the growth phase. Accounting according to EN 16449 follows the -1/+1 method: carbon bound in biomass is credited as -1 at harvest, as +1 at combustion or biological degradation. With use periods over 50 years (typical for load-bearing structures), a temporary CO₂ sink results.

Hemp Insulation: Hemp fiber insulation materials from Steico or Caparol achieve thermal conductivity λD values of 0.040 W/mK at bulk density 30-40 kg/m³. The fibers are stabilized with approximately 15% polyester support fiber (necessary for dimensional stability), which limits recyclability — thermal utilization is possible, material recycling not yet at industrial scale. GWP (A1-A3): -1.2 kg CO₂eq/kg insulation material; at 0.20 m insulation thickness (U-value 0.20 W/mK) this corresponds to -9.6 kg CO₂eq/m². Fire behavior: Class E according to EN 13501-1, installation only in non-combustible constructions or with fire protection cladding.

Straw Bale Construction: Load-bearing straw bale walls according to ÖNORM B 1600 (Austria) or as infill in timber frame constructions achieve U-values of 0.12 W/mK at 40 cm wall thickness. Straw bales from Stora Enso (compressed square bales, 450 kg/m³) show a GWP of -24 kg CO₂eq/m² (functional unit: exterior wall U=0.12 W/mK, 50 years). Critical issues are moisture protection (vapor-permeable plaster systems required) and biological durability — limit moisture equivalent content < 20% to prevent mold. Approvals exist in D-A-CH via individual building permits, general regulatory approval is still lacking.

Clay Building Materials: Clay plasters and bricks are fully recyclable: after deconstruction they can be reworked with water and reused without quality loss. Claytec offers clay hollow brick with λ = 0.47 W/mK (worse than aerated concrete with 0.09 W/mK, therefore suitable only for interior walls or multi-layer constructions). GWP: 18 kg CO₂eq/m³ (A1-A3) — lower than fired brick (230 kg CO₂eq/m³), but higher than wood (-180 kg CO₂eq/m³ including biogenic storage). The moisture-regulating effect (sorption isotherm Class II according to DIN EN ISO 24353) measurably improves indoor climate: 30% reduction in peak air exchange rate at identical relative humidity.

Market penetration 2026: NawaRo insulation materials reach 6% market share (DACH), concentrated on single and two-family houses. In multi-story residential construction, mineral insulation materials (stone wool, EPS) still dominate due to lower costs (EUR 12-18/m² vs. EUR 22-35/m² for hemp) and established approvals.

Material Passport and Digital Building Resources Inventory (Madaster)

The Building Resources Passport (GRP) of the DGNB documents type, quantity, location, and condition of installed materials with the goal of making resources transparent for future use cycles. It comprises three levels:

  1. Product Information: Material name, manufacturer, EPD number, mass/volume
  2. Installation Information: Building component ID (IFC classification), floor, accessibility (detachable/non-detachable)
  3. Circularity Assessment: Recycling potential (A-D), pollutant burden, residual value forecast

The Madaster platform digitalizes this data BIM-based. Architects upload IFC models, the software analyzes building components (by IFC entity: IfcWall, IfcSlab etc.), assigns materials (automatic recognition via material library with >10,000 EPDs) and calculates:

  • Material Circularity Indicator (MCI): 0-100%, assesses proportion of recycled inputs and recyclability of outputs
  • Embodied Carbon: Sum GWP (A1-A3) of all building components in t CO₂eq
  • Residual Value: Forecast of material value at deconstruction (2026: EUR 18/ton concrete steel, EUR 2/ton concrete rubble RC-2, EUR 95/m³ softwood C24)

Since April 2023, DGNB awards 15 points in criterion ENV1.6 (Deconstruction and Recycling) for a complete material passport. Requirements include:

  • Documentation of at least 80% of building component mass (according to DIN 276 cost group 300)
  • Specification of connection technology (screwed/nailed/glued/cast)
  • Hazardous substance inventory according to LAGA M23 (particularly asbestos, PAH, PCB in existing buildings)

Practical example: A residential building with 2,400 m² floor area contains according to Madaster analysis 1,850 tons of material, of which 1,120 tons concrete, 340 tons masonry, 180 tons metal, 85 tons wood, 75 tons insulation, 50 tons glass. The MCI is 38% (average new construction: 28%), Embodied Carbon 520 tons CO₂eq (217 kg CO₂eq/m² floor area — 12% below DGNB reference value for residential buildings). Estimated residual value at deconstruction in 50 years: EUR 42,000 (inflation-adjusted 2026).

Knauf and Wienerberger announced in 2025 that they will provide Madaster-compatible datasets for all core products from 2027 onwards — a step that will significantly accelerate the creation of material passports.

DGNB, BNB, LEED — What the Certifications Require in 2026

Building certifications assess sustainability holistically; building materials are one aspect. The weighting differs significantly:

DGNB Version 2023: Environmental impacts account for 22.5% of total points (ENV topic field). Of these, building materials account for: ENV1.1 "Environmental product declaration of the building" (16.3%), ENV1.6 "Deconstruction and Recycling" (3.1%), ENV2.3 "Responsible Resource Extraction" (3.1%). Calculation method: Environmental product declaration according to DIN EN 15978, accounting over 50 years (residential buildings) or 30 years (office buildings). Reference values for Gold certification (new residential building):

  • GWP total: < 12.5 kg CO₂eq/(m² floor area·year) — corresponds to 625 kg CO₂eq/m² floor area over 50 years
  • Primary energy non-renewable (PENRT): < 180 kWh/(m² floor area·year)
  • Ozone Depletion Potential (ODP): < 8×10⁻⁸ kg R11-eq/(m² floor area·year)

The tightening compared to DGNB 2020 is 18% in the GWP limit value. This is achieved through higher RC rates, timber hybrid construction (mass timber decks instead of reinforced concrete) and optimized insulation thicknesses (U-values 0.15-0.18 W/m²K instead of 0.24 W/m²K).

BNB 2023 (Assessment System for Sustainable Construction for Federal Buildings): Identical calculation methodology to DGNB, but stricter limits. New office and administrative buildings, target GWP: < 10 kg CO₂eq/(m² net floor area·year) at reference service life 50 years. The net floor area is approximately 75% of floor area, effectively this means 10 / 0.75 = 13.3 kg CO₂eq/(m² floor area·year) — slightly stricter than DGNB Gold. Additionally, BNB requires: Hazard avoidance according to REACH Candidate List (exclusion of 233 Substances of Very High Concern SVHC), timber from 100% certified sources (FSC/PEFC), RC content of mineral building materials ≥ 10 wt.%.

LEED v4.1 BD+C: Materials are evaluated in the area "Materials and Resources" (MR), maximum 13 of 110 points. Difference to DGNB: No normative GWP limits, but point awards based on percentage share (based on construction costs) of products with EPD, recycled content, regional sourcing (< 160 km transport distance) or C2C certificate. Minimum 5 EPDs required for 1 point, 20 EPDs for 2 points. Advantage: More flexible, no absolute CO₂ threshold. Disadvantage: No incentives for ambitious GWP reduction, merely for documentation.

In DACH, DGNB dominates with 4,200 certified projects (as of Q1 2026), LEED has 380 projects (mostly US investors), BNB has 1,850 federal buildings.

EU Green Deal and EU Taxonomy 2026

The EU Taxonomy Regulation (EU 2020/852) defines when an economic activity is ecologically sustainable. For new building construction (Taxonomy Activity 7.1), tightened technical assessment criteria (Technical Screening Criteria, TSC) apply from January 1, 2024:

  1. Primary Energy Requirement: At least 10% below national Nearly Zero-Energy Building standard (in Germany: GEG 2023 minus 10%)
  2. Life Cycle Assessment: For buildings > 5,000 m² floor area, an LCA according to EN 15978 must be conducted. The average GWP over 50 years must be documented; threshold values apply from 2027 (not yet finalized, draft: < 15 kg CO₂eq/(m² floor area·year) for residential buildings)
  3. Circular Economy: At least 70% (by mass) of arising non-hazardous construction and demolition waste is prepared for reuse, recycling or other material recovery

Essential is the Do No Significant Harm (DNSH) principle: the building may not significantly impair any of the six environmental objectives (Climate mitigation, Climate adaptation, Water, Circular economy, Pollution prevention, Biodiversity). Specifically, this means: Exclusion of refrigerants with GWP > 675 (affects older F-gases), prohibition of SVHC-containing building products at concentration > 0.1%, land sealing maximum 60% of site area.

The EU Building Performance Directive EPBD 2024 (Energy Performance of Buildings Directive, amendment from January 1, 2025) supplements the Taxonomy with minimum standards for existing buildings: By 2030, all non-residential buildings must achieve at least energy efficiency class E (to be implemented nationally), by 2033 class D. This necessitates energy retrofits with insulation materials — a demand driver for sustainable alternatives to EPS (GWP: 3.8 kg CO₂eq/kg) such as wood fiber (GWP: -1.1 kg CO₂eq/kg).

The Substitute Materials Regulation and the Circular Economy Act were adapted in 2025 to ensure EU Taxonomy compliance. Public contracting authorities must consider life-cycle costs (including CO₂ shadow price of EUR 180/ton CO₂eq) as an award criterion in tenders over EUR 5 million since January 1, 2026 — a mechanism that makes low-carbon concrete from Heidelberg Materials or Holcim competitive despite 8-12% higher investment costs.

Comparison Table: CO₂ Balance Per Building Component (Status Q2 2026)

Building Component / Function Conventional Solution GWP A1-A3 [kg CO₂eq/m²] Sustainable Alternative GWP A1-A3 [kg CO₂eq/m²] Reduction [%]
Exterior Wall (U=0.18 W/m²K) Aerated Concrete 36.5 cm + ETICS EPS 16 cm 89 Timber Frame 16 cm + Wood Fiber 24 cm (Steico) -12 -113%
Interior Load-Bearing Wall Calcium Silicate Brick KS