A word from the experts

From efficiency to frugality, a brief history of environmental performance in construction

November 2021

Expert

Kateryna Kuzmenko

Head of Research & Development Architecture

The concept of environmental performance in construction has long been reduced to the energy efficiency of the building's operating phase, that is to say to the energy used for heating, lighting, water, etc. etc.

This vision comes mainly from the historical context of the emergence of the regulatory framework, developed and put in place following the first oil shock of 1971, an event which marks Western society by the awareness of the finitude of the planet's energy resources. Energy is becoming a matter of concern as well as the main object of the regulatory framework. Therefore, from one version of the standard to another, the requirements for thermal insulation increase to double the thickness of the walls, gradually lowering the energy consumption of the operating phase. In other words, the reduction in operational energy is obtained by increasing the quantity of materials used, by precisely illustrating the phenomena of impact transfer and pollution transfer in the building's life cycle.

Life Cycle Analysis

The phenomena of impact transfer and pollution transfer are part of the theoretical framework of the environmental assessment method Life Cycle Analysis (LCA). In short, the method consists of tracing all the flows of resources and energy necessary for the operation of a system from the extraction of the raw material to the end of life (see figure 1). These flows are then translated into environmental impacts according to several categories: climate change (carbon footprint), toxicity, pollution in water and air, ionizing radiation, etc. The method thus makes it possible to quantify these environmental impacts, as well as to identify the transfers of impact from one phase of the life cycle to another and the transfers of pollution from one category of impact to another. Returning to the example of the introduction: the reduction of operational energy is obtained by increasing the insulation material, ensuring that the impact of this material (relating to the extraction, transformation and implementation) may be equal or even greater than the impact of the energy saved during the operation phase. In other words, the total impact on the life cycle does not decrease, but only moves from the operational phase to the previous phases (impact transfer), also modifying the type of pollution produced by the system (transfer pollution relating to energy to that relating to materials).

Figure 1. Six main stages in the building life cycle.

In the construction sector, we can particularly distinguish the operational impact of the building, linked to the operation phase and the intrinsic impact (sometimes gray impact), linked to the previous phases of the extraction of primary materials, transformation, transport and construction.

As a general rule, the phenomena of impact transfer and pollution transfer occur systematically following partial environmental optimization, that is to say an optimization addressing either a single phase of the life cycle (eg the operating phase of buildings) or a single impact category (eg energy or carbon).

As a result, each of the eco-design strategies developed to date in the construction sector contains several transfers of impact and pollution. This was the case with the over-insulation of the casing and the double skin systems, described above; This is also the case for wood construction, 3D printing, material recycling and the reuse of construction elements. In other words, one environmental problem is systematically replaced by another and therefore the strategy of truly effective eco-design over the entire life cycle remains to be developed.

From Efficiency to Frugality

The current proliferation of environmental considerations around greenhouse gas emissions, waste production, urban sprawl, scarcity of raw materials, etc., is causing a semantic shift in what is considered to be a sustainable strategy. Indeed, the vocabulary of efficiency and performance, specific to the energy field, seems to gradually evolve towards the notion of frugality, more adequately representing all of the contemporary issues. In formal terms, frugality provides an image of a sober or even austere architectural object, thrifty in resources and materials, self-sufficient like post-carbon cities. Frugality is therefore a new efficiency.

However, despite this semantic shift, the initial challenge remains the same: to be frugal throughout the life cycle and to avoid new transfers of impact and transfers of pollution. Again, a truly frugal design and build strategy has yet to be developed.

Release date : Mercredi 17 Novembre 2021

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