The building and public works sector directly contributes to the environmental impact of human activity because of the significant quantity of resources it uses (buildingmaterials, energy, water) and the corresponding pollution (waste, smoke, waste water). It also makes an indirect contribution by possibly adding transport requirements (e.g. building a tertiary building far from public transport facilities), curbing waste sorting (e.g. a residential building without sufficient space for selective collection), and increasing electricity demand (extension of urban lighting, electric heating or heat pumps), etc. The “eco-techniques’’ considered in this chapter are therefore not restricted to construction techniques. Managing flows of matter and energy is also crucial.