PhD success for Chenfei Liu

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Dr Chenfei Liu standing in a woodland clearing

Congratulations to Dr Chenfei Liu for being awarded her PhD in February 2022. Chenfei’s thesis was entitled ‘Evaluating Passivhaus EnerPHit Retrofit Strategies for Low-Rise Suburban Dwellings in China's Hot Summer - Cold Winter Climate Region’.

China is the world’s largest energy consumer, and the biggest source of energy demand in China is the building sector, which accounts for around 47% of the country's total energy consumption and around 51% of carbon emissions. The area with the fastest growth in building energy demand in China is the central southern hot summer - cold winter climate region. In this area there are many residential buildings that are structurally sound but which have very poor energy performance. Undertaking an eco-retrofit programme on these dwellings could lead to significant improvements in both occupant thermal comfort and reduced energy demand.   

The Passivhaus retrofit standard (EnerPHit) focusses on achieving ultra-low operational energy consumption. However, examples of Passivhaus and EnerPHit buildings are rare for hot summer – cold winter climates, and this is particularly true for central southern China. In her study, Chenfei investigated the energy savings, carbon emission reductions and cost savings that might accrue from retrofitting, to the EnerPHit standard, a case study dwelling located in China’s hot summer - cold winter climate region. External weather and indoor thermal conditions of the case study building were monitored for twelve months, and these data were used to calibrate a digital twin energy model of the dwelling. The model was used to evaluate retrofitting the existing building to the EnerPHit standard, which gave energy savings of 90% for heating and 73% for cooling. Next, different combinations of retrofitting measures were evaluated for four different build scenarios to find how the EnerPHit criteria could be met using the fewest building materials. Finally, the retrofitting plans for the case study building were evaluated from carbon and cost points of view through detailed life cycle carbon and cost assessments, and indicated that savings of up to 81% in carbon emissions and 83% in energy costs could be achieved.

Chenfei has now taken up a research post in the Welsh School of Architecture, Cardiff, where she will investigate a retrofit project that combines a façade system with renewable energy generation. 

Chenfei has published her work in two leading international journals, presented papers at two major international conferences and has had a third paper accepted for the PLEA 2022 conference in Santiago, Chile, in November 2022:

Liu C, Mohammadpourkarbasi H and Sharples S (2021) Evaluating the potential energy savings of retrofitting low-rise suburban dwellings towards the Passivhaus EnerPHit standard in a hot summer/cold winter region of China, Energy and Buildings, 231, 110555                                             

Liu C, Sharples S and Mohammadpourkarbasi H (2021) Evaluating insulation, glazing and airtightness options for Passivhaus EnerPHit retrofitting of a dwelling in China's hot summer-cold winter climate region, Energies, 14, 6950 

Liu C, Mohammadpourkarbasi H and Sharples S (2020) Analysing energy savings and overheating risks of retrofitting Chinese rural dwellings to the Passivhaus EnerPHit standard. Proc. PLEA 2020, 35th International Conference on Passive and Low Energy Architecture, Vol. 3, 1757-1762, A Coruña, Spain, 1-3 September

Liu C, Sharples S and Mohammadpourkarbasi H (2019) Analysing the benefits and challenges of retrofitting rural dwellings in Hunan, China to the Passivhaus EnerPHit standard. Proc. SBE19 Conference, pp 1-8, Cardiff, 24-25 September 2019 IOP Conf. Ser.: Earth Environ. Sci. 329 012008