Multi-family Buildings Research Articles

Road to net zero: Greenness of Leadership in Energy and Environmental Design and California Green Building Standards Code in the multifamily sector

AbstractThis study evaluates the effectiveness of Leadership in Energy and Environmental Design (LEED) and California Green Building Standards Code (CALGreen) sustainability programs in reducing greenhouse gas (GHG) emissions in multifamily buildings. We find that CALGreen effectively reduces GHG emissions by 7.2%–11.6%. However, among properties completed during the CALGreen period (on or after 2015), LEED‐certified properties exhibit 14.1%–20.8% higher GHG emissions compared to non‐LEED‐certified buildings. We attribute this result to the emphasis on theoretical design versus actual energy performance of those programs. Furthermore, our research reveals that LEED‐certified buildings completed before the implementation of CALGreen command a rent premium of 4.7%–5.4%. However, this LEED premium diminishes during the CALGreen period. Non‐LEED properties completed during the CALGreen period show limited evidence of rent premiums.

Imitation learning with artificial neural networks for demand response with a heuristic control approach for heat pumps

The flexibility of electrical heating devices can help address the issues arising from the growing presence of unpredictable renewable energy sources in the energy system. In particular, heat pumps offer an effective solution by employing smart control methods that adjust the heat pump’s power output in reaction to demand response signals. This paper combines imitation learning based on an artificial neural network with an intelligent control approach for heat pumps. We train the model using the output data of an optimization problem to determine the optimal operation schedule of a heat pump. The objective is to minimize the electricity cost with a time-variable electricity tariff while keeping the building temperature within acceptable boundaries. We evaluate our developed novel method, PSC-ANN, on various multi-family buildings with differing insulation levels that utilize an underfloor heating system as thermal storage. The results show that PSC-ANN outperforms a positively evaluated intelligent control approach from the literature and a conventional control approach. Further, our experiments reveal that a trained imitation learning model for a specific building is also applicable to other similar buildings without the need to train it again with new data. Our developed approach also reduces the execution time compared to optimally solving the corresponding optimization problem. PSC-ANN can be integrated into multiple buildings, enabling them to better utilize renewable energy sources by adjusting their electricity consumption in response to volatile external signals.

Supporting sustainability assessment of building element materials using a BIM-plug-in for multi-criteria decision-making

The environmental crisis requires the immediate implementation of accurate and robust sustainable solutions throughout the building life cycle. Life Cycle Sustainability Assessment (LCSA) is a scientifically recognised method that integrates the triple dimensions of the life cycle approach, and thereby enabling the evaluation of the performance of mitigation strategies implemented in building projects. However, implementing the LCSA in buildings is limited by the weighting of environmental, economic, and social dimensions to select the best option regarding the numerous materials available. In order to fill this knowledge gap, the paper aims to present the developed Smart BIM3LCA tool, which supports multi-dimensional assessment during the project´s early design steps. Automatic integration of the LCSA, a multi-criteria decision-making tool such as TOPSIS, and building information modelling (BIM), was developed to support the selection of building materials. The BIM plug-in was then validated through its application to a multi-family residential building to select the most sustainable materials during the project´s early design stage.

Long-Term Comparative Life Cycle Assessment, Cost, and Comfort Analysis of Heavyweight vs. Lightweight Construction Systems in a Mediterranean Climate

Massive construction systems have always characterized traditional architecture and are currently the most prevalent, straightforward, and cost-effective in many Mediterranean countries. However, in recent years, the construction industry has gradually shifted towards using lightweight, dry construction techniques. This study aims to assess the effects on energy consumption, comfort levels, and environmental sustainability resulting from the adoption of five high-performance construction systems in a multi-family residential building: (i) reinforced concrete structure with low-transmittance thermal block infill; (ii) reinforced concrete structure with light-clay bricks and outer thermal insulation; (iii) steel frame; (iv) cross-laminated timber (CLT); (v) timber-steel hybrid structure. To achieve this goal, a multidisciplinary approach was employed, including the analysis of thermal parameters, the evaluation of indoor comfort through the adaptive model and Fanger’s PMV, and the quantification of environmental and economic impacts through life cycle assessment and life cycle cost applied in a long-term analysis (ranging from 30 to 100 years). The results highlight that heavyweight construction systems are the most effective in terms of comfort, cost, and long-term environmental impact (100 years), while lightweight construction systems generally have higher construction costs, provide lower short-term environmental impacts (30 years), and offer intermediate comfort depending on the thermal mass.

Optimizing Energy Efficiency with a Cloud-Based Model Predictive Control: A Case Study of a Multi-Family Building

The Energy Performance of Buildings Directive (EPBD) has set a target to achieve carbon-neutral building stock and generate 80% of its electricity from renewable sources by 2050. While Model Predictive Control (MPC) can contribute significantly to energy flexibility in buildings, its remote implementation remains relatively unexplored, especially in the residential sector. The purpose of this research is to demonstrate the reliability, robustness, and computational efficiency of a cloud-based application of an MPC called Smart Energy Management (SEM) on a multi-family residential building. The SEM was tested on a virtual building model in TRNSYS using an open-source distributed event streaming platform for data exchange and synchronization. Simplified models for thermal behavior prediction, including an R3C3 model of the building, were developed in C++. The SEM was evaluated in eight scenarios with varying weather conditions, optimization criteria, and runtime periods. The results demonstrate that the SEM maintains stability and robustness over a 2-week period with a 15-minute planning resolution while ensuring thermal comfort. The C++ implementation of the optimization algorithm enables SEM deployment on low-spec servers, supporting cost-effective applications in real buildings with minimal intervention.

Reducing the cost of home energy upgrades in the US: An industry survey

Decarbonizing the US residential building stock requires a substantial acceleration in home energy upgrades. Numerous barriers exist to accelerating adoption of efficient and electric building technologies, but foremost among these is high upfront costs. This study uses an industry survey delivered to a sample of home energy professionals to examine promising cost reduction strategies across a range of project types, including HVAC, water heating, and envelope/insulation projects. The survey included quantitative and qualitative questions to collect evidence on the estimated cost reduction potential of these strategies and their likelihood of use in the construction industry. The 167 survey respondents included contractors, energy consultants, architects, manufacturers, and others with experience in delivering energy upgrades in single-family and multifamily buildings in the US. Results show that significant cost reductions are achievable by minimizing additional infrastructure costs (such as replacing electric panels), streamlining project planning/management, and deploying innovations that simplify installation. We find that for a typical deep retrofit project, including heat pumps for space and water heating in addition to envelope upgrades, the strategies could result in a total installed cost reduction of nearly 50 %, dramatically improving the customer economics of such a project. This research makes a novel contribution to the literature on strategies to reduce the costs of residential retrofits. We discuss how our study's insights on the highest-value cost reduction strategies for home energy upgrades can further accelerate their uptake in the US housing stock.

Case study: structural feasibility analysis for a reinforced concrete building

Currently, the residential building sector in Brazil is experiencing continuous growth, despite the adverse impacts caused by 2 years of the Covid-19 pandemic. Therefore, there is a demand for structural projects that enable the execution of these works from a structure that is viable from the point of view of safety, good conditions of use, comfort and economy. Technical and practical knowledge is a fundamental requirement for a good project, combined with skill in a technological analysis and sizing tool. Having said that, the present work proposed to develop the analysis and structural design, with the help of the Brazilian software TQS®, of a multi-family residential building in reinforced concrete, using both linear and nonlinear static analyses. The central motivation was to address structural challenges and ensure that the design complies with Brazilian standards, thereby improving the quality and safety of residential buildings. The work sought to follow all the design steps of a structure in order to meet the requirements recommended by Brazilian standards. Based on the analyses, it was possible to adopt solutions for the various structural problems that arose during the design and, finally, obtain the final document with all the details of the structure.

Evaluation of transition to 100% electric vehicles (EVs) by 2052 in the United States

With the rising need to transition from fossil fuel consumption to renewables, the transportation industry is foreseeing large-scale adoption of electric vehicles (EVs). According to various studies, the petroleum resources will last until or around 2052. Utilizing the US Federal Highway Administration (FHWA) published data on the number of registered vehicles by each state, the profile of vehicles by 2052 was forecasted using a time series. The vehicle profile comprised vehicles by each type classified as automobiles, buses, trucks, and motorcycles. This future profile became the basis of the quantification of total EVs by the end of 2052. Based on the available fuel economy data published by the US Department of Energy, the average energy consumption per mile (kWh/mile) of each vehicle type was factored into the energy demand calculation for 100% electrification by 2052. A roof-top solar photovoltaic system is easy to install on unoccupied roof space for US house owners. Obtaining the capacity of such a roof-top solar PV system acts as a good decision-making criterion for both house owners and developers. However, for city-dwellers living in multi-family residential buildings, the potential of utilization of roof-top solar PV becomes a subject of future work when effective sharing of resources for local power generation by renewables and development of community-shared EV charging infrastructure is concerned. How well EVs performed against internal combustion engine (ICE) vehicles in terms of fuel efficiency and reduced carbon emissions is a driving factor for this transition. For energy demand calculations, a base model was framed, and results were obtained by utilizing mathematical and statistical tools. After accounting for the effects of improved fuel efficiency or reduced energy consumption by EVs over time, the model was modified to obtain revised energy demand and, thus, effective energy generation required. Accordingly, the capacity of EV charging infrastructure required by each state determined the need for preparation by utility companies and local jurisdictions. With limitations on battery size and thus increased frequency for drivers to return for charging, additional fast chargers (level 3) at existing gasoline stations become an option that requires further assessment.

Transformation Pathways: Drumul Taberei Neighbourhood - a Positive Energy District?

Abstract Positive Energy Districts (PED) have surged in prominence amidst Europe’s ambitious climate targets and the fluctuating energy landscape, influenced notably by geopolitical uncertainties such as the Ukraine conflict. Aligned with European and national priorities, which emphasises the renovation of its housing stock as part of the Renovation Wave initiative, PED emerges as a viable solution for urban areas. However, the challenge remains in how PED can address energy poverty, promote renewable energy, and align with renovation priorities of the outdated infrastructures (including buildings). The KINETIC project addresses PED transformation challenges at the neighbourhood level by deploying an intensive co-creation process for identifying key transformation directions. The Romanian DEMO area (along with DK and IT study cases) is the Drumul Taberei neighbourhood in Bucharest Sector 6, a dense neighbourhood composed of multifamily buildings realised in the 60s and 70s during the communist regime. The area needs comprehensive regeneration and renewal initiatives. If proven feasible through mathematical modelled data paired with strategic integrated planning, the outcomes of KINETIC for the Drumul Taberei neighbourhood will be able to revolutionise the future rehabilitation project of collective housing districts in Romania, and beyond. The paper will outline PED transformation pathways stemming from initial co-design workshops involving local stakeholders. It will also explore collaboration and investment prospects between municipality-housing associations and NGOs. Given the privately owned housing estate and state-funded rehabilitation, the project will assess innovative models to meet PED’s ambitious goals.

Renovating Post-First-Energy-Regulation Housing: Achieving Nearly Zero-Energy buildings under typical and extreme warm conditions in a temperate European city

Decarbonising the built environment is essential for achieving the 2050 European objectives. Multi-family buildings comprise nearly half of Europe’s building stock, yet there is no regulation mandating all housing renovations to be Nearly Zero-Energy Buildings (NZEBs). This paper highlights the role of NZEB renovation for residential buildings constructed between the first energy regulations, after the first oil crisis, and the EPBD 2002 implementation (post-first-energy-regulation housing), as a pivotal factor towards energy transition. In Spain, this period (1980–2006) encompasses approximately 45% of existing dwellings. A case study was conducted in a city with a Cfb temperate climate, focusing on the most representative residential typology of the target period: the linear block. The study evaluates its current state and defines potential measures to meet NZEB requirements, achieving zero consumption when renovation of thermal envelope is combined with heat recovery systems, heat pumps, and PV panels.This research is based on energy simulations for two climate scenarios: the typical meteorological year (TMY, official series 1970–2000) and the most extreme warm year (EWY, 2022) in Spain. Results indicate active cooling systems are necessary for NZEB renovations in Spanish Cfb climates. Furthermore, low-temperature radiators significantly reduce heating consumption, while splits are the most suitable cooling systems. This study shows Spain is not adequately preparing its housing stock to face climate change, as most typical renovation works are based on official weather files that need updating to reflect harsher summer conditions. Finally, the study aims to encourage new policies and enhance existing regulations to address rising temperatures and heatwaves.

Sustainability Assessment of Harvesting Rainwater and Air-Conditioning Condensate Water in Multi-Family Residential Buildings under Various Conditions in Israel—A Simulation Study

The environmental impacts and water savings of different configurations of non-potable domestic water use (toilet flushing and laundry), sourced from rainwater harvesting (RWH) and air-conditioning condensate water (ACWH), in multi-family buildings in Israel are examined. Two building types differing in specific roof areas, and three climatic sub-regions were modeled. RWH satisfied 23 and 46% of the water demand for toilet flushing and laundry in high-rise and low-rise buildings, respectively. Air conditioning is used almost daily during Israel’s hot and dry summers. Hence, the combined RWH-ACWH system saved 42 and 64% in high- and low-rise buildings, respectively. Displacing desalinated seawater, a significant water source in Israel, with alternative water sources lowered the environmental impacts with an increase in storage, up to a certain volume, beyond which impacts started rising. The same infrastructure is used during winter for RWH and for ACWH during summer; thus, combining the two exhibits significant water savings, with marginal extra costs while lowering the environmental impacts.

Understanding Party Size in Ride-Hailing: Solo Versus Group Travel

Emerging mobility technologies, like ride-hailing, are underrepresented in travel behavior surveys. Consequently, travel demand modelers have often resorted to simplistic solo-traveler assumptions or relied on aggregate trip size factors within activity- and agent-based models. To address this gap and help modelers understand ride-hail party size, this study analyzed data collected from a 2021 to 2022 household travel survey in the greater Twin Cities (Minneapolis–St. Paul, MN) region. Ride-hail trips were paired with person-, household-, and trip-level attributes to provide context for both single-party and multiparty ride-hailing. Binary logistic regression models indicated that shared micromobility users, households with more children, renters in large multifamily buildings, and individuals with at most a high school education were significantly more likely to use ride-hailing for group travel than for solo trips. A hurdle regression for party size count revealed that lower-income households, while less likely to use ride-hailing, were more likely to opt for group travel and form larger parties than other income cohorts. These findings offer insights into who takes ride-hailing for group travel, enabling policy makers to devise strategies targeting solo, unshared ride-hailing without negatively affecting large groups.

Effectiveness of Cool and Green Roofs Inside and Outside Buildings in the Brazilian Context

Several studies have assessed the thermal performance of green and cool roofs. However, few have comprehensively addressed Brazilian buildings and climates, considering indoor and outdoor environments. Considering three Brazilian cities, this study aims to assess the performance of green and cool roofs compared with traditional fibre cement roofs in a typical multifamily residential building. Energy consumption, thermal comfort, and outside surface temperature were assessed using computer simulation. The results show that the cool roofs performed better in cities with warmer climates (e.g., Cfa and Aw), reducing electricity consumption by up to 24.8% compared with traditional roofs. Green roofs are better suited for colder climates (e.g., Cfb), with up to 28.2% energy savings. Green roofs provided the highest percentage of thermal comfort hours in all climates. Cool and green roofs provided hourly reductions in outside roof surface temperature of up to 16.5 °C and 28.4 °C, respectively, compared with the traditional roof. This work reinforces that the choice between these two roof types for each city depends on the parameter used for comparison. Based on the relevant information applied to Brazilian buildings and representative climates presented, this work provided recommendations for urban planning policies and building regulations in Brazil.

Hybrid solar-biomass residential micro – Combined Heat and Power systems driven by the Partially Evaporating Organic Rankine Cycle – A case study in Southern Europe

In this study, a novel hybrid solar-biomass residential micro – Combined Heat and Power system driven by the Partially Evaporating Organic Rankine Cycle is proposed and its operation is simulated, by applying an in-house numerical model. The simulation tool is applied for a test case in Athens, Greece, where the micro-CHP system operates to cover the annual energy demand of a multi-family building. The proposed cogeneration unit covers 97.10 % and 25.85 % of the modeled building’s annual Space Heating and electricity demand, respectively, by using renewable energy sources. The annual average total energy and exergy efficiencies are equal to 53.33 %, and 10.35 %, respectively, while the power cycle can achieve thermal efficiencies as high as 9.73 %. Competitive Levelized Cost of Electricity (0.072–0.133 €/kWhel), and Levelized Cost of Heat (0.036–0.067 €/kWhth) values are estimated, with a PayBack Period between 5.17 and 9.64 years. The environmental impact of the proposed hybrid micro-CHP is anticipated to be significant, rising to 46.25 kWh of Primary Energy Savings, and 31.22 kg CO2-eq. reduction in carbon emissions per m2 of residence annually.

Energy impact of heating electrification in mid-rise multifamily buildings in mixed-humid climates

Energy impact of heating electrification in mid-rise multifamily buildings in mixed-humid climates

Social mix in Zagreb’s large housing estates

In Western and Northern Europe, post-war large housing estates (LHEs) stand out as areas of segregated and minority-populated housing, and have faced numerous attempts of reconstruction with the idea of social mixing. LHEs in Central and Eastern Europe had different developmental pathways. The heterogeneous structure of these estates has persisted until today, but due to the systematic neglect and aging, the estates are threatened by physical and social deterioration. The analysis is based on a survey conducted in Croatia in 2022 on two types of housing estates (socialist and post-socialist; N (Zagreb = 657). The results confirm that the social composition in both types of estates is mixed, with a predominance of middle-class residents and without pronounced social differences. The residential satisfaction is high, so the majority of residents are stayers. Nevertheless, certain regeneration policies should be adopted because the population of the socialist LHEs is aging, which could jeopardize the present heterogeneity and make maintenance of multifamily buildings more challenging, thus contributing to further deterioration of the estates.

Assessing the emissions reduction potential and economic feasibility of small-scale (

Small-scale combined heat and power (CHP) for residential applications has been demonstrated in different regions throughout the world. CHP can enable resilience in energy supply and serve as a transitional technology as the grid progresses to higher fractions of low carbon electricity production. However, there are very limited feasibility assessments in the context of US climate zones, policies, and economic factors. To address this gap, we assess how the economic feasibility and emissions impact of a small-scale, natural gas CHP system compares considering the local electrical grid in seven climate zones and six subgrid regions across the United States. This is accomplished using an in-house Python program alongside EnergyPlus that is used to size the CHP and/or thermal storage systems according to representative electrical and thermal demand profiles for multifamily residential buildings, optimizes CHP and thermal storage energy dispatch throughout the year to meet demands, assesses the system’s economic feasibility, and calculates the carbon emission reduction or increase relative to the local electrical grid. For the baseline cases considered, carbon emissions can be reduced by up to 12% for regions with high required thermal load and/or electricity derived from high carbon emitting sources. In many scenarios, carbon emissions increased. Furthermore, the economic feasibility of the systems, even considering recent incentives, remains a significant barrier. The resulting Python program is open-source and designed for use by both researchers and building owners to conduct their own small-scale CHP feasibility assessments.

Investigation of a high-temperature combination heat pump for lower-cost electrification in multifamily buildings

The development of space and water heating combination heat pumps capable of generating water temperatures high enough for convective heat emitters will enable more cost-effective and equitable decarbonization solutions for electrifying multifamily buildings. In this paper, multifamily building models and a charge-sensitive mechanistic cycle model of a combination heat pump are developed, and the system performance is predicted based on the models. Unlike other state-of-the-art residential heat pumping equipment, the modeled combination heat pump using an economized, fluid-injected variable-speed compressor can achieve higher temperature lifts of 40° – 85°C, with lower installation costs and complexity. The model predicted heating coefficient of performance (COPh) is 2.1 at an ambient temperature of −15°C with a high-temperature lift of nearly 85°C, and a seasonal coefficient of performance in heating mode (SCOPh) ranges from 2 – 4 for different locations. The system shows 30% – 90% lower CO2eq emissions over a condensing gas boiler and 9% – 13% lower projected installation costs than two separate space and water heat pumping appliances.

Integration of Photovoltaic Systems for Energy Self-Sufficient Low-Rise Multi-Family Residential Buildings in Republic of Korea

Integration of Photovoltaic Systems for Energy Self-Sufficient Low-Rise Multi-Family Residential Buildings in Republic of Korea

Investigation of source ambiguity of floor noises in a box-frame concrete building from the perspective of junction attenuations: A real case field experiment

This study investigated impact source ambiguity in box-frame multifamily buildings, prevalent in densely populated areas, by examining the transmission of heavy-impact noise and its relationship with junction attenuations across five floors. Contrary to the decline in noise levels with increased distance from the impact source, our findings uncover an intriguing deviation in the behaviour of vibration response levels. Surprisingly, vibrations are often intensified, rather than diminished, with distance. Notably, upon examining each room, instances where non-structural or thin concrete walls exhibited the highest vibration responses were frequently observed. Such instances were particularly prevalent in rooms not directly adjacent to the impact source. This trend markedly impedes residents’ ability to pinpoint the origin location of impact noises. This study reveals an unexpected weakening and reversal of distance attenuation in vibration, linked to the increasing number of valid flanking paths as the junction distance grows. The findings suggest that increasing slab thickness for noise insulation may unintentionally complicate source identification due to diminished junction attenuation in thicker horizontal components compared to vertical ones. To enhance acoustic comfort in such housing, this study recommends minimizing valid flanking paths through improved junction design, addressing an often-overlooked issue of source ambiguity of floor noises.