Environmental impact evaluation of energy saving and energy generation: Case study for two Dutch dwelling types

The existing building stock is a logical target to improve the level of sustainability of the built environment by energy saving measures. These measures typically entail a decrease of operational energy demand, mainly by adding building components such as insulation packages and energy generating devices. Consequently, material related environmental impact might create a collateral disproportionate burden, which is not well addressed in current assessment methods. In an attempt to evaluate this effect, two common dwelling types in the Netherlands, a terraced and a detached dwelling, have been redesigned to the level of Zero Energy Building in four scenarios, and the environmental impact of these scenarios has been assessed, expressed in embodied energy and related to the carrying capacity, expressed in embodied land (m²·a). The lowest environmental impact is achieved in the scenario with an average U-value of 0.29 W/m²K and 35 m² and 75 m² of PV modules for the terraced and the detached dwelling, respectively. In this scenario, added embodied energy is 3.4 GJ/m² and embodied land is 308,777 m²·a land for the terraced dwelling and 5.2 GJ/m² and 653,644 m²·a land for the detached dwelling. This evaluation indicates that a focus on only energy efficiency improvement shows a collateral material related environmental impact which should be embedded in the complete environmental assessment of buildings.