Ecological Materials in Modern Construction

Sustainable construction has moved from a niche trend to a standard demanded by both the market and European regulation. The Construction Products Regulation (CPR) and the Energy Performance of Buildings Directive (EPBD) have accelerated the adoption of lower-impact materials. Ecological materials offer tangible advantages: better thermal and acoustic comfort, improved indoor air quality, and higher long-term resale value.

Timber is one of the few construction materials that acts as a CO₂ sink throughout its service life. Ramage et al. (2017) demonstrated that replacing steel and concrete with wood in mid-rise buildings can reduce embodied carbon emissions by 15–25% [1]. One cubic metre of structural timber stores approximately one tonne of carbon dioxide.

To ensure that timber extraction does not contribute to deforestation, two internationally recognised certification schemes exist: FSC (Forest Stewardship Council) and PEFC (Programme for the Endorsement of Forest Certification). According to the Mass Timber Market Report (Stora Enso, 2023), the cross-laminated timber (CLT) market grew at 22% per year in Europe between 2018 and 2023, driven by carbon regulation and demand for lightweight structural systems [2].

In construction, certified timber is used in structural frames (CLT, glulam, solid timber), external and internal joinery, cladding and floor systems. Its key advantage over steel or concrete is a negative carbon footprint, though it requires proper treatment against moisture and insects to ensure durability.

Conventional concrete accounts for 8% of global CO₂ emissions, primarily through Portland cement clinker production. Chatham House (2018) estimates that, to meet the Paris Agreement climate targets, the cement industry must cut its emissions by 16% by 2030 relative to 2014 levels [3].

Recycled aggregate concrete (RAC) replaces 20–50% of virgin aggregates with material from construction and demolition waste (CDW), reducing both extraction demand and the volume of debris sent to landfill. Silva, de Brito and Dhir (2014) demonstrated that good-quality recycled aggregates do not compromise the mechanical properties of concrete when the replacement rate stays below 30% [4]. Pacheco-Torgal et al. (2013) compile the dosage limits accepted by the main European standards in their Handbook of Recycled Concrete and Demolition Waste [5].

In Spain, standards UNE-EN 206 and EHE-08 regulate the use of recycled aggregates in structural concrete. For non-structural applications — fill, floor slabs, blinding concrete — the replacement rate can reach 100%.

Schiavoni et al. (2016) conducted a comparative review of 22 insulation materials for the building sector, concluding that natural-origin insulants have an embodied energy 40–70% lower than conventional synthetics such as expanded polystyrene (EPS) or spray polyurethane [6].

Expanded cork (ICB): harvested from cork oak bark without felling the tree. Density 110–120 kg/m³, thermal conductivity 0.040 W/mK, excellent acoustic performance and high moisture resistance. Used in facades, roofs and floors.

Sheep wool: thermal conductivity 0.035–0.040 W/mK, hygroscopic — regulates indoor humidity — naturally fire-retardant and 100% biodegradable. Cabeza et al. (2011) found that natural insulants with higher thermal mass outperform low-density synthetics in summer under Mediterranean climate conditions [8].

Hemp: fast-growing crop (harvested in 4 months), pesticide-free and a CO₂ sink during growth. Ip and Miller (2012) calculated that hemp-lime walls in the UK have a negative carbon footprint of −35 kgCO₂e/m² over their life cycle [7]. In rigid panel or lime-mixed spray form, thermal conductivity ranges from 0.040 to 0.048 W/mK.

The WHO estimates that people spend 90% of their time indoors, where pollutant concentrations can be 2–5 times higher than outdoors. Allen et al. (2016) showed, in a controlled study with office workers, that reducing VOC levels and increasing ventilation improves cognitive function scores by up to 61% [9].

The AgBB (Committee for Health-related Evaluation of Building Products, 2021) sets VOC emission limits for construction products in the European market, classifying materials by their total VOC content (TVOC) measured at 28 days [10]. Ecological paints are formulated with water bases, mineral pigments and natural binders — casein, vegetable oils, waxes — with VOC content below 1 g/L, compared to 300–400 g/L in conventional alkyd paints.

Reference certification labels include the EU Ecolabel (Flower), the German Blue Angel and Cradle to Cradle for construction materials.

Allwood et al. (2012) propose evaluating construction materials across three dimensions: production impact (carbon footprint, water and energy consumption in manufacturing), in-use performance (durability, maintenance, hygrothermal regulation) and end of life (recyclability, compostability, reuse potential) [11].

Environmental Product Declarations (EPDs, per ISO 14025) are the technical reference document for comparing materials objectively. In Spain, the DAP Construcción platform aggregates the EPDs of the main manufacturers in the sector.

Sustainable construction is not only a question of materials: bioclimatic design, building orientation and efficient water management are equally decisive. But choosing materials wisely is the first step, and today the range of ecological options is wide enough that neither performance nor budget need be sacrificed.

1. Ramage, M.H. et al. (2017). The wood from the trees: The use of timber in construction. Renewable and Sustainable Energy Reviews, 68, 333-359. DOI: 10.1016/j.rser.2016.09.107
2. Stora Enso (2023). Mass Timber Market Report 2023. Helsinki: Stora Enso.
3. Chatham House (2018). Making Concrete Change: Innovation in Low-carbon Cement and Concrete. London: The Royal Institute of International Affairs.
4. Silva, R.V., de Brito, J. & Dhir, R.K. (2014). Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production. Construction and Building Materials, 65, 201-217. DOI: 10.1016/j.conbuildmat.2014.04.117
5. Pacheco-Torgal, F. et al. (2013). Handbook of Recycled Concrete and Demolition Waste. Woodhead Publishing. ISBN: 978-0-85709-682-1. DOI: 10.1533/9780857096906
6. Schiavoni, S. et al. (2016). Insulation materials for the building sector: A review and comparative analysis. Renewable and Sustainable Energy Reviews, 62, 988-1011. DOI: 10.1016/j.rser.2016.05.045
7. Ip, K. & Miller, A. (2012). Life cycle greenhouse gas emissions of hemp-lime wall constructions in the UK. Resources, Conservation and Recycling, 69, 1-9. DOI: 10.1016/j.resconrec.2012.09.001
8. Cabeza, L.F. et al. (2011). Experimental study on the performance of insulation materials with PCM in building envelopes. Energy and Buildings, 43(12), 3243-3250. DOI: 10.1016/j.enbuild.2011.06.005
9. Allen, J.G. et al. (2016). Associations of Cognitive Function Scores with CO₂, Ventilation, and VOC Exposures in Office Workers. Environmental Health Perspectives, 124(6), 805-812. DOI: 10.1289/ehp.1510037
10. AgBB (2021). Health-related Evaluation of Emissions of Volatile Organic Compounds (VVOC, VOC and SVOC) from Building Products — AgBB Scheme 2021. Berlin: Deutsches Institut für Bautechnik.
11. Allwood, J.M. et al. (2012). Sustainable Materials: With Both Eyes Open. Cambridge: UIT Cambridge. ISBN: 978-1-906860-05-9.