Environmental Impacts of Multi-Storey Buildings Using Different ...

- 65 -6.3.4 Impact AssessmentTotal primary energy and GWP were the two impact categories calculated for each buildingtype. The results for each building are presented for the following life cycle stages: initialmaterial production and use, maintenance, transport, operation over the 60 year lifetime of thebuilding/s and end-of-life.The results are based on the Base scenario, as described in sections 6.3.4.1 to 6.3.4.3. Theresults for the reutilisation scenario and transport scenarios are presented in section 6.3.5.6.3.4.1 Total Primary Energy Use and GWPThe total primary energy and GWP contributions from each building can be seen in Figure 6.4and Figure 6.5 below. The Timber buildings have lower contributions to global warming thanthe Steel and Concrete buildings; the results for the Steel building are 30% higher than for theTimberPlus building. The TimberPlus building has the lowest primary energy use over its lifecycle, followed by Concrete, Timber and Steel respectively. The total primary energy use forthe Steel building is 7 % higher than the TimberPlus building.The main contribution to each impact category is during the building’s operational phase, inall buildings contributing over 85% of the primary energy use and over 70% of the GWPimpacts. The difference between each building’s transport, maintenance, and end-of-life makerelatively little difference but the differences in initial embodied energy are significant. InTable 6.6 and Table 6.7, the total figures for each stage of the life cycle are presented.When breaking down the total impact of the buildings into life cycle stages, it can be seen thatthe operational energy is the largest figure. It makes up 87% (Steel) to 94% (TimberPlus) ofthe total energy use of the buildings, and 72% (Concrete) to 78% (TimberPlus) of the totalemissions that contribute to GWP. Embodied energy makes up 5% (TimberPlus) to 11%(Steel) of the total primary energy use and embodied GWP makes up 9% (TimberPlus) to23% (Steel) of the impact from greenhouse gas emissions. Maintenance is the only othersignificant contributor in each category. End-of-life (transport of materials to landfill and thelandfilling process as well as storage of carbon and potential release of methane) is around0.5% for primary energy use and ranges from 2% (Concrete) to -9% (TimberPlus) for theGWP. Transport of materials to site makes up around 0.3% of primary energy use and 0.5%of GWP.The differences in the buildings’ embodied energies and embodied global warming potentialscan be seen below (in Table 6.6 and Table 6.7). The Steel building has the highest values forboth categories, followed by Concrete, Timber and TimberPlus. However, taking into accountthe full life cycle (including operation energy) the order for the energy use is different. Due toincreased operational energy, the total primary energy use for the Timber building becomesgreater than for the Concrete building. The order of the total GWP values remains the same.This point has been expanded in the inventory section (6.3.3.3).