Public defence in Building Technology, M. Sc. Hatef Hajian

Title of the thesis: Dynamic heating control in power and energy reduction and renovation of multifamily apartment buildings

Doctoral student: Hatef Hajian
Opponent: Prof. Jurgis Zemitis, Riga Technical University, Latvia
Custos: Prof. Heidi Salonen, Aalto University School of Engineering, Department of Civil Engineering

This study focused on energy renovation, specifically retrofitting existing buildings with energy-efficient technologies to reduce energy consumption, peak power demand, and greenhouse gas emissions. 

The study aimed to support renovation goals through two main objectives. The first objective was to investigate how dynamic heating control systems can reduce energy and power needs in existing buildings. The second objective was to assess the effectiveness of Finnish renovation practices funded by Asumisen rahoitus ja kehittämiskeskus (ARA). 

The research is particularly relevant to current efforts in energy efficiency, smart building technologies, and sustainable renovation practices. It aligns with global priorities to reduce energy consumption and carbon emissions in the building sector. The emphasis on renovation highlights the need to upgrade existing buildings to meet modern energy efficiency standards, making this research a valuable contribution to both academic and practical applications. 

Key findings include that lowering HC temperatures resulted in marginal energy savings of 0.6 kWh/m²a (0.8% of space heating energy) while maintaining indoor temperatures at 21°C, revealing limited potential for energy savings without compromising thermal comfort. The dynamic control algorithm reduced heating power by over 10% during domestic hot water peaks without affecting indoor air comfort. Additionally, introducing a primary side flow limiter reduced heating sizing power by 5.5% and district heating mass flow rate by 12.4% under designed outdoor conditions, demonstrating more efficient use of district heating capacity. 

Analysis of common renovation packages, including heat pumps and window replacements, revealed that official EPCs often overestimated pre-renovation energy use and savings by nearly double due to overestimated infiltration and ventilation. While ARA-funded renovations generally achieved good energy savings, the typical subsidy covering around 25% of shallow renovation costs fell below 10% for deep renovations, making them economically unfeasible. 

These findings offer valuable insights for enhancing building energy efficiency, particularly in energy audits, smart building technologies, HVAC system design, and renovation strategies. The conclusions suggest a comprehensive approach to improving energy efficiency through smart controls, efficient system designs, and targeted renovations.

Key words: Building energy renovation, Space heating energy, Power reduction, Dynamic heating control, ARA renovation subsidies

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Contact information: Hatef Hajian, [email protected], tel.: +358449892211

Doctoral theses of the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49