As integral components of urban infrastructure, buildings play a crucial role in maintaining occupant well-being, especially during extreme weather conditions. This research presents a model predictive control (MPC) approach to harnessing the energy flexibility of buildings by utilising their thermal mass to cost-effectively manage the energy use. The study compares two apartment buildings located in the Nordic climate of Helsinki, Finland: one built in the 1970s and a modern positive energy building (PEB) with a high-performance envelope exceeding the minimum requirements of national building regulations. Three control strategies are evaluated for building thermal mass activation: Proportional-Integral (PI) control as a standard strategy for thermal comfort, RuleBased Control (RBC) as a cost-based benchmark strategy and an advanced MPC as an innovative energyflexible strategy for cost-savings. The three investigated control strategies are implemented by interfacing IDA ICE building energy performance simulation software with the programming environment, Python as a master controller. The study aims to optimise the operation of the building’s energy systems in real-time, minimising energy costs while maintaining comfort constraints by adjusting temperature setpoints based on dynamic weather conditions and occupant behaviour by applying the adaptive thermal comfort model. The results, obtained from simulations, demonstrate that the MPC provided the highest cost savings, particularly under high and fluctuating price conditions. In the 1970s building, MPC achieved up to 29.9 % cost savings compared to PI control, while RBC achieved up to 17.2 % savings. In the modern PEB, MPC resulted in up to 14.8 % cost savings, with RBC achieving up to 7.9 % savings. These findings highlight MPC’s potential to improve energy efficiency and resilience in buildings, especially in cold climates

The pursuit of sustainable energy solutions has become a critical focus in addressing the challenges of climate change and urbanization. This Special Issue provides a comprehensive overview of recent research in the field of energy and sustainability, encompassing diverse topics such as urban energy planning, short-term electrical load forecasting, energy resilience, energy flexibility, energy efficiency, nearly zero-energy buildings and districts, and the development of Positive Energy Districts (PEDs). The studies included in this Special Issue demonstrate the importance of combining innovative technologies, community engagement, and policy support to achieve energy efficiency and sustainability goals. By exploring the practical applications and impacts of these advancements, this Special Issue fosters a holistic understanding of the current state of energy research and its potential to drive positive change in urban environments. This Special Issue includes a total of 16 papers covering different aspects of building and district planning, technologies and their economics, building design and retrofitting, citizen engagement and the collection of energy data, energy resilience, and energy flexibility.

The future buildings and society need to be resilient. This article aims to propose a novel concept of the energy resilience framework and implement a color-based rating system to quantify and rate the energy resilience performance of buildings in Nordic climates. The objective is to conduct a comparative analysis between old (1970s) and new (2020s) single-family buildings integrated with renewable energy sources and storage, assessing their energy resilience performance for heating during power outages, under extreme and typical climatic conditions. The study utilizes dynamic simulation of the buildings and renewable energy systems, conducting parametric studies to calculate proposed resilience indicators and rate their resilience performance, employing both passive and active methods. The total costs of the design variables are also calculated for economic evaluation. Given the complexities arising from climate change, the article uses a simplified method to synthesize regional climate to consider extreme climate change impacts on energy resilience performance. For the old building lacking PV, the robustness duration increased from 1 h to 3 h, and the degree of disruption (DoD) varied from 0.545 to 0.3 in extreme cold to warm climate scenarios, with the higher DoD number indicating worse performance. The impact of the season within the same climate scenario is also evident, as the habitability and robustness durations increased during spring compared to winter. The resilience improved with PV and battery. The new building showed that the robustness duration increased from 3 to 15 h, habitability durations increased, and the DoD varied from 0.496 to 0.22 from extreme cold to warm climates without renewables and storage. With the integration of PV and battery, the new building was able to achieve a lower DoD and better performance with lower PV and battery capacity, compared to the old building. Furthermore, utilizing the color grading method (red to green), optimal technical solutions and corresponding design variables were identified for each building type and climate scenario that could support decision-making. The total cost of the optimal solutions varied, as new buildings required lower costs to reach optimal performance. However, for optimal resilience performance during extreme cold climate scenarios, higher costs are required for each building type. The proposed resilience framework, indicators, color grading system, and costing could potentially support improvements in building regulations, ensuring the development of optimally resilient buildings, particularly in the face of extreme climatic conditions.

: The future buildings and society need to be resilient. This article aims to propose a novel concept of the energy resilience framework and implement a color-based rating system to quantify and rate the energy resilience performance of buildings in Nordic climates. The objective is to conduct a comparative analysis between old (1970s) and new (2020s) single-family buildings integrated with renewable energy sources and storage, assessing their energy resilience performance for heating during power outages, under extreme and typical climatic conditions. The study utilizes dynamic simulation of the buildings and renewable energy systems, conducting parametric studies to calculate proposed resilience indicators and rate their resilience performance, employing both passive and active methods. The total costs of the design variables are also calculated for economic evaluation. Given the complexities arising from climate change, the article uses a simplified method to synthesize regional climate to consider extreme climate change impacts on energy resilience performance. For the old building lacking PV, the robustness duration increased from 1 h to 3 h, and the degree of disruption (DoD) varied from 0.545 to 0.3 in extreme cold to warm climate scenarios, with the higher DoD number indicating worse performance. The impact of the season within the same climate scenario is also evident, as the habitability and robustness durations increased during spring compared to winter. The resilience improved with PV and battery. The new building showed that the robustness duration increased from 3 to 15 h, habitability durations increased, and the DoD varied from 0.496 to 0.22 from extreme cold to warm climates without renewables and storage. With the integration of PV and battery, the new building was able to achieve a lower DoD and better performance with lower PV and battery capacity, compared to the old building. Furthermore, utilizing the color grading method (red to green), optimal technical solutions and corresponding design variables were identified for each building type and climate scenario that could support decision-making. The total cost of the optimal solutions varied, as new buildings required lower costs to reach optimal performance. However, for optimal resilience performance during extreme cold climate scenarios, higher costs are required for each building type. The proposed resilience framework, indicators, color grading system, and costing could potentially support improvements in building regulations, ensuring the development of optimally resilient buildings, particularly in the face of extreme climatic conditions.