Public defence in Electrical Power and Energy Engineering, M.Sc. Xinyi Hu

The title of the thesis: Holistic renovation strategies for cold climate buildings: simulation-based insights into decarbonization and cost-effectiveness 

Thesis defender: Xinyi Hu
Opponents: Prof. Thomas Olofsson, Umeå University, Sweden, and Prof. Jakub Kolarik, DTU, Denmark
Custos: Prof. Matti Lehtonen, Aalto University School of Electrical Engineering

The building sector is a major contributor to global energy use and CO₂ emissions, accounting for about 40% of total energy use in the EU and 21% in China. In cold climates, where space heating dominates end-use demand, renovating existing buildings is essential for long-term decarbonization. Given the high demand for deep renovations, more systematic and scalable concepts are needed to implement holistic renovation strategies across building types and national contexts. 

This doctoral thesis proposes a simulation-based multi-objective optimization framework. The framework supports selecting optimal individual and holistic renovation solutions, assessing economic viability of mechanical ventilation systems, and sizing decentralized and hybrid renewable-powered systems. Two case studies, a rural residential building in northern China and a public kindergarten in Finland, demonstrate the framework’s applicability across different settings. 

The results indicate that holistic renovations enhance envelope thermal performance while simultaneously improving indoor air quality and promoting cleaner energy use. These total optimized solutions achieve greater reductions in both CO₂ emissions and life-cycle costs than individual measures. The results also demonstrate interactions among electrified heating systems, on-site renewable generation, and HVAC renovation measures. The thesis offers practical guidance for promoting low-carbon, cost-effective building systems in cold climates.

Key words: Building energy renovation, indoor climate, cold climate, simulation-based optimization, life-cycle cost, renewable energy, ventilation, heat pumps, electrification

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact:
xinyi.hu@aalto.fi