In 2012 the United States Army Corps of Engineers (USACE) adopted an air barrier tightness standard that requires new buildings and buildings undergoing major renovation to be tested and subsequently to pass a stringent building air barrier tightness test to make sure the building air leakage does not exceed 0.25 cfm/ft2 at 0.3 in. w.g. (4.6 m3/h/m2 at 75Pa) pressure difference between inside and outside air. Since the introduction of this requirement, more than 1000 buildings have been constructed and renovated with the average leakage rate of ~0.15 cfm/ft2 at 0.3 in. w.g. (2.7 m3/h/m2 at 75Pa) after tightening. Analysis conducted by U.S. Army Engineer Research and Development Center (ERDC) researchers and USACE engineers shows that improved airtightness of the building envelope yields significant energy savings, especially in extreme (cold and hot/humid) climates, and also helps to reduce the risk of interstitial condensation and to improve building resilience (temperature degradation inside the building) when the building’s power supply, heating, or cooling is interrupted. Improved airtightness also reduces the amount of outdoor air supply required for over-pressurization to prevent infiltration of outdoor air or contaminants. Based on a comprehensive review of research results and economic analyses, it is proposed that a more stringent requirement to building air tightness of 0.15 cfm/ft2 at 0.3 in. w.g. (2.1 m3/h/m2 at 75Pa) be considered in the future, particularly for extreme climates. This paper describes recent research results that show the importance of improved building air tightness

As climate change worsens energy insecurity, resilience to long-term blackouts in cold climates is increasingly critical. Blackouts can compromise indoor heating, leading to serious habitability, health, and survivability risks. Yet, most existing regulatory frameworks lack clear definitions of minimum habitability and survivability thresholds, and often under examine the role of demographic and social factors. This study presents a novel, integrated, human-centric method that combines a single-stage occupants survey—designed to assess energy resilience awareness, occupant-defined habitability and survivability thresholds, and key demographic factors—with a detailed building performance simulation model. Survey data was collected from 378 participants residing in a cold climate region (Finland) and is integrated with simulations of both old and renovated residential buildings, incorporating various passive and active energy systems, including building envelope, photovoltaics (PV), battery storage, and heat pumps. This interdisciplinary approach enables a comprehensive techno-economic analysis that effectively bridges social perceptions with technical assessments of energy resilience. Moreover, a new set of energy resilience indicators is proposed, specifically tailored for buildings in cold regions. These indicators form the basis of a color-based classification scheme used to visualize simulation outcomes and compare the resilience performances of the buildings. Survey results show that heating (i.e., habitability) is the top need in Finland, followed by electrical loads (i.e., survivability). Habitability thresholds differ by age, gender, location, and building type, ranging from 15 °C to 19 °C. Older buildings fail to meet these needs, especially for people over 50 years old. In passive conditions, dissatisfaction among older adults reaches 100 % and elevated psychological stress values. Renovations and renewable energy systems greatly improve resilience, reducing low heating risks and physiological stress—though at a 94 % cost increase. Dissatisfaction with habitability drops from 100 % to 1 %, and survivability improves from 0 % to 98 %. For adults aged 41–61+, dissatisfaction drops to 90 % (men) and 98 % (women) with building renovation, and with PV-battery systems, it falls to 0 % for both. This research offers a transferable, occupant-centered framework for assessing energy resilience, bridging technical, social, and economic dimensions to guide building adaptation in other cold climates and Nordic countries.

Conventional methods of studying houses’ Energy Performance Certificates (EPCs) typically fail to investigate the impact of interrelated contextual elements instead fixating exclusively on the specific attributes of individual houses. This study presents a new method that combines network graph analytics (NGA) with interactive visual analytics to investigate hidden linkages at the individual house level. Our proposed platform collects and analyses data related to housing attributes, creates a network based on the links between these attributes, and employs sophisticated graph algorithms to provide visual representations. Users have the ability to dynamically choose postcodes, metrics, and attributes, which, in turn, generate layouts of networks that provide valuable insights. The visualisation utilises colour gradients and node metrics to improve the comprehensibility of energy performance areas. The platform enables homeowners and stakeholders to comprehend the interrelationships between aspects such as neighbouring housing features, and house infrastructure. The results prove the efficacy of the strategy by giving a collection of case studies that encompass various Energy Performance Certificates (EPCs) ranging from A to G. Each case study demonstrates the evolution of network architectures and visual assessments, showcasing the energy performance linked to certain EPC ratings. The platform offers a user-friendly interface for stakeholders to investigate and understand attribute relationships.

This Reprint focuses on the concepts, fundamentals, and defines the concept of nearly/net/zero and positive energy buildings/communities/districts and their impact on the built communities. It also provides details on energy efficiency of buildings in communities and districts, the HVAC systems, short- and long-term energy storage, renewable energy integration, and controls. As the built environment and businesses are moving towards energy efficiency, flexibility, and self-sufficiency so these concepts are also discussed in detail. In addition to this, while looking at the present energy crisis due to the economy, climate change, and policy changes. The concept of energy resilience is also discussed. The development of future-proof buildings and the built environment is of particular interest; hence, this concept is also presented. Finally, the economic, social- and policy-related aspects are included in the Reprint to provide a comprehensive solution to various interested stakeholders, parties, and, in general, to society. Users’ acceptance and engagement in communities and districts.

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.