We analyzed the primary energy use and carbon dioxide (CO2) emission over the lifecycle of the Limnologen building, an eight-storey apartment building in Växjö, Sweden made with a wood structural frame. The analysis covers all the life cycle phases of the building, including the acquisition of raw materials, the processing of raw materials into building materials, the assembly of materials into a ready building, the occupation or use of the building, the demolition of the building and the disposal of the demolition material.

We found that the operation of the building uses the largest share of lifecycle energy use, becoming increasingly dominant as the life span of the building increases. The type of heating system plays a major role for primary energy use and CO2 emission, since it affects what type of energy supply chains are used. A biomass-based district heating systems achieves low primary energy use and very low CO2 emissions. During the construction phase of the building, more bioenergy can be obtained from residues from the wood products chain (forest residues, wood processing residues, and construction site residues) than is used to produce the building. Additional bioenergy can be obtained at the end of the building life cycle if wood-based demolition residues are recovered and used as biofuel. The use of recovered biofuels to substitute for fossil fuels significantly reduces the net emission of CO2. We need to adopt a life cycle perspective involving construction, the use and demolition of buildings as well as energy supply when thoroughly evaluating the primary energy and climatic impacts of buildings.