Introduction

In a building project, the decisions with the greatest environmental impact are not made at the end of the process, but at the beginning. When the structural system, the construction typology and the degree of industrialization are defined, not only the performance of the building is being determined, but also a large part of its future environmental footprint. These decisions affect the emissions associated with the manufacture of materials, the construction process and, to a lesser extent, maintenance and the end of life.

In recent decades, sustainability in building has been mainly associated with the reduction of energy consumption in the use phase. This approach has allowed significant advances and today it is common to design buildings with very low energy demands. However, as operational energy decreases, the relative weight of embodied emissions increases, i.e. emissions associated with the production of materials and the construction of the building.

In newly built residential buildings with high energy performance, the structure becomes one of the main sources of environmental impact, both in terms of the amount of material it concentrates and the energy required for its manufacture. For this reason, the structural system is a strategic point from which to act if you want to reduce the overall environmental impact of the building from its origin.

Answering the question “which construction system is more sustainable?” is not trivial. There is no universally valid solution, since factors such as the climatic context, regulatory requirements, cost, availability of materials or the organization of the construction process come into play. In this scenario, Life Cycle Assessment (LCA) becomes a key tool for objectively comparing different alternatives, assessing their impacts throughout the useful life of the building.

With this approach, the Construyendo MaderAulA project is developed, whose objective is to generate comparable technical references through the economic and environmental analysis of the same building solved with different construction systems, keeping its functional and energy performance constant.

Role of ITeC in Construyendo MaderAulA

Construyendo MaderAulA is a European collaborative project that addresses the analysis of industrialized construction solutions, with special attention to wood systems, comparing them with conventional and other non-wood-based industrialized solutions. The project does not aim to promote specific material, but to provide technical knowledge that allows informed decisions to be made in the initial phases of the project.

In this context, the ITeC assumes a central role in the methodological definition of the study and in obtaining comparable indicators. Based on coherent and homogeneous construction models, ITeC develops the measurement states, links the construction elements with reference databases and obtains economic and environmental indicators with complete traceability.

This approach makes it possible to simultaneously analyse the cost of material execution and the associated environmental impacts, avoiding partial approximations or simplifications that could distort the comparison between construction systems.

Methodology

The study is based on the definition of a typology-technology matrix that allows comparing different construction solutions applied to the same building. It starts with a base building, geometrically and functionally defined, which is resolved by different structural and construction systems. All versions of the building are designed to achieve a high energy rating, so that the differences in results are not due to variations in energy performance, but to the construction system itself.

The following systems are analysed, among others:

• conventional reinforced concrete structure,
• steel structure with prefabricated elements,
• CLT wood panel structure,
• lightweight timber frame structure,
• mixed structure, combining reinforced concrete and wood.

The analysis is applied in two different climatic locations, Soria and Barcelona, representative of climatic zones tested according to the Technical Building Code. This dual location makes it possible to assess how the climate interacts with the construction system and how it influences the phase of use of the building within the overall balance.

Based on the construction models, the measurement statements and the lists of materials are drawn up, which are linked to the ITeC BEDEC database. Through the TCQ and TCQi tools, the economic and environmental indicators are obtained, following a Life Cycle Analysis logic aligned with the UNE-EN 15978 standard. The reference period considered is 50 years, including the stages of product manufacturing, construction, use and end of life.

From these premises, within the Construyendo MaderAulA project, a comparative analysis based on Life Cycle Analysis arises, applied to the same building solved with different construction systems, which allows the comparison of the different impacts throughout its life cycle.

Results

The results of the study show that the environmental impact of a building is not concentrated in a single phase of its life cycle. In most of the solutions analysed, the material manufacturing stages (A1-A3) and the use phase associated with energy consumption (B6) concentrate most of the energy and total emissions. This reinforces the need to act both on the energy efficiency in use and on the choice of materials and construction systems.

The proportion between phases A1-A3, A5 and B6 is not the same in the energy graph as in the embodied emissions graph. This is because, depending on when the energy is used for the building, the energy mix and, therefore, the emissions associated with the same number of kWh consumed can change.

A relevant contribution of the study is to demonstrate the importance of comparing construction systems under equivalent performance conditions. By requiring all versions to achieve a similar energy rating, it avoids attributing environmental advantages or disadvantages to a system that actually stem from differences in insulation, systems, or energy configuration. This methodological control allows the differences observed to be directly related to the construction system and the materials used.

The comparative analysis shows that wooden structural solutions generally have lower impacts in the manufacturing phases compared to conventional solutions, while the differences in the use phase are smaller as they are buildings with equivalent energy performance. It is also observed that certain mixed solutions can offer interesting trade-offs between economic cost and reduction of environmental impact, which underlines the importance of analysing each case from a global perspective and not just from a single indicator.

Conclusions

The study confirms that the sustainability of a building cannot be evaluated exclusively on the basis of its energy performance in the use phase. In a context in which high-efficiency buildings are becoming more and more common, decisions related to materials and construction systems are gaining increasing weight in the overall environmental balance.

Incorporating Life Cycle Assessment in the early stages of the project allows us to identify opportunities for improvement when the changes are still technically and economically viable. Faced with corrective approaches applied at the end of the design, this type of analysis facilitates more rational and transparent decision-making, based on comparable and traceable data.

In a regulatory scenario that is moving towards the mandatory incorporation of life cycle environmental impact indicators, work such as those developed in Construyendo MaderAulA contributes to preparing the sector, providing solid technical references and practical tools to design buildings with a lower environmental impact from their conception.

 

FSC Spain, Diputación de Soria, Cesefor, Asfoso, AEICE and ITeC are the partners of #ConstruyendoMaderaula, which has the support of the Biodiversity Foundation of the Ministry for the Ecological Transition and the Demographic Challenge (MITECO) within the framework of the Recovery, Transformation and Resilience Plan (PRTR), funded by the European Union – NextGenerationEU.

#ProyectosPRTR #PlanDeRecuperación #NextGenerationEU