Life Cycle Assessment and straw construction

Life Cycle Assessment, or LCA, is an environmental accounting and management approach that considers all the aspects of resource use and environmental releases associated with an industrial system from cradle to grave.
 Specifically, it is a holistic view of environmental interactions that covers a range of activities, from the extraction of raw materials from the Earth and the production and distribution of energy, through the use, and reuse, and final disposal of a product. LCA is a relative tool intended for comparison and not absolute evaluation, thereby helping decision makers compare all major environmental impacts when choosing between alternative courses of action.
 

Why is LCA important for the construction sector?

In the last 20 years energy efficiency has become an increasingly important aspect of the planning and evaluation of buildings, as well as a subject of legislation within the EU. As a result, the operational energy consumption of new and refurbished buildings has decreased considerably during this time.

Figure 1 shows the ratio between the operational energy (for regulated uses such as heating, ventilation, cooling and lighting according to the EPBD) during the use phase, and the embodied energy due to the fabrication of the building products as well as their end of life (EoL). The use phase for older buildings dominates all other life cycle stages. Today, new buildings may consume less than 15 kWh final energy for heating per m² per year if they comply with the Passivhaus standard. The new types of ‘energy surplus’ or ‘positive energy’ building may even be net producers of energy. Therefore, the ratio between operational impacts (the use phase) and the embodied impacts (e.g. for production and EoL) is now more or less balanced.

These changes emphasize that as well as optimizing the use phase of a building it is also important to consider the embodied impacts of the materials used in its construction. As a result, the Energy-Efficient Buildings Initiative now needs to consider a life cycle perspective ‘from cradle to grave’, with energy consumption being only one environmental aspect within a multicriteria framework that includes, for example, waste generation and climate change. Straw as an insulation material could meet this challenge by offering high levels of insulation associated with a low environmental impact material.
 

Case study : Notre-Dame de Bon Secours school

The Middle School in Binche has been the first school using straw for insulation in Wallonia (Belgium). The building is in use since 2017 with a usable area of 532 sqm for 8 classrooms. Straw is used for walls based on prefabricated panels with clay plaster provided by Paille-Tech company. Roof and ground slab use cork as insulation. Ventilation is provided by a dual flow unit with a heat exchange efficiency of 80%. Air tightness was estimated by blower door test at 0.51 ACH, lower than Passive house requirement (0.6 ACH). The outer windows are made of doubleglazed glass. The heating consumption has been calculated by energy building simulation and is estimated at 37 kWh/m².yr.
 
LCA of the School
 
 
 
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  • Carole de Fays

    Chargée de mission projets européens

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