This study is based on the dissertation “Environmental impact of Lodenareal passive house residential complex” from DI Julia Reisinger and deals with the question as to whether passive houses could also be deemed to have an environmental impact because of the increased energy required for the manufacture, repair and replacement of their construction. Is there really a positive CO2 footprint, if you compare the red (operating) energy to the grey (construction) energy and how does the environmental footprint of a passive house compare to the environmental footprint of a similar building based on low-energy house standards? The results of my dissertation show that the increased material costs in the Lodenareal passive house residential complex contribute to a considerable energy saving and are therefore profitable from an ecological perspective.
At the Lodenareal passive house residential complex, the proportion of grey energy in the overall energy is approx. 50–60% for greenhouse potential and just 50% for primary energy demand. This additional grey energy required (for a conventional building, the grey energy demand is only 10–20%), however, results in a considerable reduction in heating energy consumption and the associated emissions during use. It takes 54 years for the red energy from the use of the building to overtake the grey energy used in its construction.
The material composition of a building has a huge influence on its grey energy. The design of a passive house with a timber construction and mineral wool insulation produces better environmental footprint results in comparison to a load-bearing solid construction. The results show that building with timber can reduce CO2 by up to 10%. Even in terms of acidification potential and the demand for non-renewable primary energy, a timber building performs better than a building in load-bearing solid construction throughout all the phases of its life cycle. However, because of the artificial drying and other stages of processing, the total primary energy required is greater for wood than for a concrete construction.
The large number of cables and pipes in a passive house means that building services contribute about 10% of CO2 emissions. Because these fittings are high-maintenance, cables and pipes must be carefully scaled even in the early planning phases for buildings. Fitting long-lasting and less high-maintenance materials can efficiently reduce the grey energy of these types of buildings.
The comparison between the passive house and the low-energy house shows that the buildings to the passive house standard are superior to the low-energy house from an environmental perspective. The passive house achieves a 5% saving on CO2 emissions compared to the low-energy house. It is only in terms of acidification potential where the passive house achieves 3% worse results than the low-energy house because of the thicker insulation and increased number of cables and pipes.
In summary, the passive house performs better in ecological terms than the low-energy house, despite the increased material costs. Compared to the calculated final energy consumption as per the energy pass, the final energy consumption of the Lodenareal passive house residential complex is high at 61.33 kWh/m2 net floor area (49.8 kWh/m2 gross floor area). According to the energy pass, the final energy consumption is 35.25 kWh/m2 gross floor area. This means the residential complex consumes 29% more heat than set out in the energy pass.