Environmental and economic multi-criteria evaluation framework of residential buildings retrofit scenarios. a case study in Ningbo

Abstract

Rapid economic development and high urbanization rates that have been present in China during the past several decades led to a drastic increase in energy consumption throughout all industries and sectors. One of the main contributors to the country’s total energy demand is the building sector, and residential buildings are responsible for nearly half of that contribution. Driven by higher living standards, growing income, and increasing urbanization, the total energy consumption of public and residential buildings is expected to continue rising. The worldwide concern for global warming, climate change, and environmental pollution problems calls for a decrease in energy demand in each country, including China. Improving the energy performance of existing residential building stock through retrofits is imperative to partially lift the pressure exerted on China’s energy sector and environment. And while in the northern part of the country pilot building retrofit projects started to occur, the southern part of China, especially Hot Summer and Cold Winter (HSCW) climate zone including Ningbo municipality, is yet to follow on this innovation.

Energy consumption decreases brought by building retrofits directly depend on the extent of the retrofits with major interventions often leading to greater energy savings and consequently building running costs reductions. On the other hand, however, complex retrofits require large initial financial investments that must be accounted for when selecting a building retrofit scheme. Considering the environmental side of building retrofits, energy demand reductions decrease the greenhouse gasses (GHG) releases, but the manufacturing, delivery, and installation of new equipment and materials generate emissions. Thus, a perfect balance must be achieved between many economic and environmental criteria to make sure that the proposed retrofits are affordable and financially and environmentally beneficial.

Accurate estimation of building energy demand and the potential effect of retrofit installation depends on various factors that include both building parameters and occupancy behaviours. The residential building sector presents numerous buildings with different construction materials, heights, forms, and shapes. All of these parameters and many others are important to consider during retrofit assessments. In addition to that, the users’ interaction with heating and cooling equipment are detrimental influencers on the energy demand in buildings, therefore, they must be accounted for in retrofit scenarios evaluation research.

This thesis explores methods to improve the energy performance of Ningbo city’s residential building stock while simultaneously addressing the aforementioned problems. Based on the analysis of the residential building stock of Ningbo municipality, 21 building typologies were created. Representative buildings from 15 of the oldest ones among them were modelled as the baseline for retrofit scenarios assessment. The local occupancy profiles including heating and cooling equipment and regime preferences were designed based on the data collected via questionnaire to ensure the energy simulation results are as close to the real ones as possible. Individual and combinatorial installation of different variations of retrofits for 12 active and passive building systems were evaluated following the developed EE Score assessment framework. The most financially and environmentally beneficial retrofit scenario was established for each analysed building topology. The developed EE Score assessment framework and its results on Ningbo city’s residential building stock can assist building stakeholders, residents, facility managing companies and governments in the decision-making process regarding suitable building retrofit scenarios selection. The other outcomes and discoveries made in this thesis can be used to expand further research aiming at improving energy performance, indoor environment quality, and occupants’ satisfaction with the buildings.

Date of Award	Oct 2022
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Ali Cheshmehzangi (Supervisor) & Wu Deng (Supervisor)