Finding the gaps in design strategies and technological advancements for net-zero energy buildings development in India

Abstract

The climate-adaptive net-zero energy building design is an effective trend for achieving a carbon-neutral environment and reducing global energy demand, especially, in India where building energy consumption recorded substantial growth in the past decade. This review article focuses on the development of net-zero energy buildings in tropical climates through the analysis of 44 real case studies. This study investigates the building envelope parameters, advance technologies, and their effectiveness on the building energy models. In the first phase of this study, fourteen net-zero energy buildings or high-performance buildings in the USA, China, and India considering energy-efficient design features and their significant effect on energy consumption have been examined. Moreover, the role of building simulation tools in improving energy efficiency is discussed. The second phase investigates the thirty best practices of net-zero energy buildings in tropical climates worldwide based on envelope choices, heating, cooling, and lighting features. Furthermore, this review discusses the evolving definitions, challenges, and inconsistencies in terminologies of net-zero energy building and illustrates India's initiatives towards net-zero development. The objectives of this review study are to highlight the challenges in building material research, advanced lighting, heating, ventilation, and air conditioning technologies, and integration of renewable energy compared to developed nations. Additionally, the gaps that are the barriers to the development of net-zero energy building in India have been identified. The review eventually concludes by providing policy recommendations and suggesting areas for future research to facilitate net-zero energy-building development in India.

Keywords

Net-zero energy building built environment strategies and technological options tropical climate case study

Introduction

Net-zero energy buildings (NZEBs) are an effective way of helping the world achieve its sustainable development, climate mitigation, and zero carbon emission goals by 2050.^1,2 The global building sector, including commercial and residential buildings, utilized ∼ 29% of total end energy by 2020.³ According to the International Energy Agency (IEA) report, energy usage in buildings is expected to rise by 32% between 2015 and 2040.⁴ Moreover, buildings were responsible for 39% of carbon emissions in 2018, with 11% attributed to the production of building materials like steel, cement and glass.^5,6

The building sector of India stands as one of the principal consumers of end-use energy.^7–9 It is continuously booming with a growth rate of 10%, against the global growth rate of 5.2%. It is predicted to add 40 billion m² of the newly built-up area by 2050.^10,11 The total built-up area of commercial buildings in India was recorded as 659 million m² in the base year 2010. It is estimated to exceed 1900 million m² by 2030.^12,13 Figure 1 depicts the annual growth rate in commercial building footprints in India.

Figure 1.

Commercial building footprint growth rate in India.^12,13

Buildings accounted for 33% of electricity consumption in India in 2018–2019. It is predicted to rise 3 to 5 times by 2031.¹⁴ India has a huge territory with a complex geographical environment that leads to vast climatic boundaries. The tropical climate covers 80% of the total country's physical boundary, where air-conditioning is required to maintain an indoor thermal environment.¹⁵ Figure 2 shows the magnitude of required cooling degree days in metropolitan cities in India compared to China and the USA. It reflects that Indian cities need higher cooling demand, which causes greenhouse gas (GHG) emissions.^16,17 India is the fourth largest carbon emission country after China, the USA, and the European Union (EU), which produced 2309.1 Mt/year of carbon emissions in 2018. India is experiencing continuous growth at a rate of 3.5%, surpassing the global growth rate of 2.6% by 2050.¹⁸ There are two approaches to reducing the escalating levels of energy consumption and carbon emissions, which are energy-efficiency management systems (EEMSs) and renewable energy sources (RESs). EEMS focuses on the combination of efficient architectural design and promoting energy-efficient measures. Whereas RES focuses on fulfilling the building operational energy demands either off-site or on-site using the RESs.^19–21

Figure 2.

Cooling demand requirement in India, China, and the USA¹⁷ (CDD: cooling degree days; RAC: room air-conditioning).

The deployment of NZEB has been considered a promising strategy for a few decades to overcome all these energy-related issues. NZEBs ensure a balance between energy consumption and generation through RESs over time while simultaneously ensuring minimum energy demands and zero carbon emissions.²² Previous research emphasized on design optimizations of building envelopes, heating, ventilation, and air conditioning (HVAC) systems, renewable energy (RE) technologies, and specific net-zero energy (NZE) strategies.^23–25 Researchers have used various simulation and optimization tools for the design of NZEBs.^26–28 Moreover, many studies demonstrated passive design features and the effectiveness of insulating materials to reduce the penetration of solar radiation and maintain an indoor thermal environment.^29,30 Researchers have also investigated the effect of natural ventilation on occupant comfort and derived the mechanism for the integration of natural and mechanical ventilation to reduce the building's cooling energy demand. Chen and Yang³¹ investigated the various types of centralized and decentralized heating and cooling systems for high-performance building design. Moreover, the application of building-integrated photovoltaic (BIPV) systems and their integration with building façades reduced the heat gain through the envelope, fulfilled building demand, and contributed to achieving net zero.^32,33 Meanwhile, a few studies exist in the literature that focused on the state-of-the-art NZEBs research on the adoption of various envelope design features and advanced energy measures for lighting, HVAC, and RE based on the practical experience of designing and operating actual case studies.

There is a lack of extensive research that illustrates the impact of active and passive design strategies on the energy consumption of commercial NZEBs in the tropical climate of India compared to the most developed nation, the USA, and the developing country, China, in real scenarios. Therefore, this study illustrates a comprehensive review of 44 certified energy-efficient/NZEB case studies located in tropical climates of different countries that reduced their energy consumption and achieved “Net-Zero” status. This review also focuses on key factors of energy savings, including the building envelope, lighting, HVAC systems, and RE technologies, which can significantly contribute to NZEB's developments and carbon-neutral environments. The main objective of this research is to investigate and analyze various real-world case studies of NZEB in tropical climates to identify their present features, climate-responsive design approaches, technology integration, and energy performance. The research further aims to establish best practices for NZEB design and technological choices specifically tailored to the tropical climate of India. The significance of this research is to identify the barriers to NZEB development in India, such as technological challenges, materials research, and the resilience of policies and standards. Finally, the policy recommendations that lead to contributing to NZEB in India have been discussed.

This article is summarized into eight major sections as depicted in Figure 3. The “Introduction” section summarizes the needs and requirements of NZEB. The “Definitions and India's initiatives towards NZEB” section demonstrates the worldwide definitions of NZEB, India's existing government policies, and the mainstream for NZEBs. The “Methodology” section includes methodology, which summarizes the selection criterion of fourteen NZEB case studies that are the best practices in tropical climates of the USA, China, and India. The “Analysis of reviewed case studies” section emphasizes on the critical comparative assessment of reviewed case studies (RCSs), accounting for key design features of passive designs, technological choices, and energy performance. The “Assessment of 30 NZEBs” section summarizes the best practices of 30 real-world high-performance NZEB case studies. The “Technological options and strategies for NZEB” section introduces the different technological options and strategies for NZEB development. The “Conclusion and policy recommendations” section illustrates the challenges and barriers at various scales to NZEB design in India and suggests policies and recommendations for future NZEB development. Finally, future research and limitations are discussed in the last section.

Figure 3.

Research outline.

Definitions and India's initiatives towards NZEB

Definitions of NZEB around the globe

A precise definition of NZEB is essential to evaluate the various design, technical, operational, and methodological approaches adopted to address the crucial aspects of enhancing building energy performance.³⁴ Singh and Verma³⁵ highlighted that the absence of standardized practices and a robust definition would result in limited actual instances of zero energy buildings (ZEBs). Therefore, this section illustrates the definitions and metrics to guide the NZEB development in India.

Previous literature reported various definitions and frameworks for the energy performance assessment of NZEB as per the region-specific conditions.^36,37 The theory of NZEB in building science was introduced in 1976 by Esbensen and Korsgaard from the University of Denmark, with subsequent definitions proposed by various countries over time.³⁸ Torcellini et al.³⁹ categorized NZEBs based on RE supply options whether on-site or off-site. Figure 4 illustrates a building equipped with passive design, energy-efficient measures, and RE supply provided through on-site or off-site generation, which is considered as NZEB (option 0).⁴⁰ Figures 5 and 6 represent the hierarchy of RE supply options, respectively.⁴¹ Table 1 shows the categorization of NZEB as per on-site and off-site availability of RES.

Figure 4.

Hierarchy of renewable energy supply options for net-zero energy building (NZEB) – (option 0).⁴⁰

Figure 5.

Hierarchy of renewable energy supply options for net-zero energy building (NZEB) – (type A – option 1) and (type B – option 2).^39,42

Figure 6.

Hierarchy of renewable energy supply options for net-zero energy building (NZEB) – (type C – option 3) and (type D – option 4).^39,43

Table 1.

Categorization of NZEB as per renewable energy supply options and RE ranking.

Supply option	Option	NZEB type	Generation option	Example
On-Site	Option 1	NZEB-A	RE sources within the building footprint.	PV installed on roof and wall, wind turbine mounted on the building roof, thermal solar heat water
On-Site	Option 2	NZEB-B	Renewable energy sources within the building boundary, are not installed in the building footprint and nor installed on the building.	PV was installed in the parking lot and open area, a small hydro and wind turbines were installed on-site, as an on-site solar-driven chiller and radiant generation system.
Off-Site	Option 3	NZEB-C	Imported RE sources from external locations to generate electricity within the building premises.	Off-site sources are utilized to import wood pellets, biomass, ethanol, biodiesel, and waste for the purpose of generating on-site electricity.
Off-Site	Option 4	NZEB-D	Acquire certified RE from an external source to power the generating station.	Utility-based wind turbine, PV panel installed off-site, and other green credit certified options.

NZEB: net-zero energy building; RE: renewable energy; PV: photovoltaic.

Consequently, each NZEB comprehensive definition and metric emphasized on sustainable development, and energy neutrality for the built environment.⁴² However, prerequisites and accreditations of NZEB vary across the nations, leading to diverse terms such as zero energy house in Denmark, energy-autonomous house in Germany, ZEB in the USA, zero carbon home in the UK, nearly ZEBs in the EU, net zero emission building in Australia, net zero energy home in Canada and ZEB in India.^44,45 In response to that, there is no one particular definition for ‘net zero’ energy buildings.²⁵ Despite heterogeneous characteristics, these definitions aim to reduce fossil fuel energy demand by maximizing RESs, optimizing building energy efficiency, and ultimately achieving the zero or nearly ZEB status.^43,46 Table 2 provides a recapitulation of all the ZEB definitions given by various developed and developing nations, international organizations, and other standards. Each country and organization used different metrics such as system boundaries (on-site or off-site RE generation); balanced demand (site energy and GHG emission); end-use and life cycle energy (operational and embodied) for measuring and evaluating the building's performance. The assessment criterion considered in Table 1 defines on-site electricity generation using RESs within the building boundaries (perimeter of the site), or the building footprint (wall and roof). Off-site electricity generation includes importing electricity generated from RESs outside the building's physical boundary or importing RESs to produce on-site electricity. Site energy addresses the RE generation equivalent to the annual operational energy demand and includes transported energy losses from the energy grid to the building utilization process. Carbon emissions are considered as CO₂ emissions resulting from the use of utilities and services in buildings, which should be compensated with RE. Operational energy is considered as the end uses HVAC and lighting energy demand of the building entire year fulfilled by the RE. Embodied energy described as total carbon emission in the entire life cycle of the building is compensated through generations of RE.^47,48

Table 2.

Summary of NZEB definitions given by various countries, and international organizations.^34,40,43

Reference	System boundary		Balanced demand		End use and life cycle energy
	On-site	Off-site	Site energy	Carbon emission	Operational	embodied
USA	✓	✓	✓		✓
European Union	✓	✓			✓
UK	✓	✓	✓	✓	✓
Japan	✓				✓
France	✓	✓			✓	✓
Germany	✓	✓			✓
Australia		✓		✓		✓
Canada	✓				✓
China	✓	✓			✓
India	✓	✓			✓
DOE	✓		✓		✓
REHVA	✓		✓		✓
EPBD	✓		✓		✓
ASHRAE	✓				✓
USGBC	✓		✓		✓
DGS	✓				✓
EPA	✓		✓		✓
ILFI	✓		✓		✓
NBI		✓	✓		✓
AIA		✓	✓		✓
IESNA		✓	✓		✓
IEA	✓			✓	✓

AIA: American Institute of Architects ; ASHRAE: American Society of Heating, Refrigerating, and Air-Conditioning Engineers; DGS: Department of General Services (DGS), California; DOE: Department of Energy; IEA: International Energy Agency; IESNA: Illuminating Engineering Society of North America (IESNA); ILFI International Living Future Institute EPA: Environmental Protection Agency, U.S.; EPBD: Directive on Energy Performance of Building; EPBD: Energy Performance of Buildings Directive; NBI: New Building Institute; NZEB: net-zero energy building; REHVA: Federation of European Heating, Ventilation and Air Conditioning Associations; USGBC: U.S. Green Building Council.

In response to that the terminology of NZEB has been characterized by different ambiguous and inconsistent calculation methods. Meanwhile, acknowledging the lack of homogeneity among the ZEB definitions requires a recognized universal definition due to ZEB becoming the main research stream across the world.⁴⁹ The absence of intrinsic consistency in the accepted ZEB not only affects the creation of an unambiguous profile for the global community and consequently a unified goal for global energy-efficient building policy but also poses significant challenges in comparing diverse solutions stemming from various contexts.⁵⁰ As a result, the core of NZEB is to reduce the building energy demand by architectural design, and energy efficiency measures and achieve the residual energy demand from RE sources. Therefore, a numerical indicator namely energy performance index (EPI) kWh/m²/year has been introduced by European countries.⁴⁴ It defines the annual primary energy use in heating, cooling lighting, ventilation, and hot water. Therefore, in this work, the authors have employed EPI as the primary indicator to assess the building's performance. Moreover, it summaries the existing NZEB's state-of-the-art related to building design, energy systems, and technical solutions and discusses the potential impact on EPI and meeting the NZEB status.

In this review, NZEB case studies that follow the definition of NZEB given by the US Department of Energy have been investigated. According to this definition, an energy-efficient building is one in which the actual annual energy consumption is either equal to or lower than the amount of on-site RE generation.

Initiatives towards NZEB in India

India has always been a country full of ethical values that focus on conserving nature. These values and practices are deeply ingrained in all Indian mythologies and have been influenced by various philosophies over the centuries. In architecture, the concept of Panchabhoota, representing the five core elements of nature, plays a crucial role and symbolizes sustainable development. Prithvi represents site efficiency, Jal signifies water efficiency, Agni represents energy efficiency, Vayu describes indoor environmental quality and Akash relates to the outdoor environmental quality.^51,52 The fundamental philosophy of NZEB emphasizes the “3Ps” (people, planet, and profit) criterion of sustainability such as social (user satisfaction), environmental (energy efficiency and CO₂ emissions), and economic (cost-effectiveness) to protect the 3Ps as depicted in Figure 7.^53–55 The Government of India has recognized the sustainability aspects of the construction sector and has implemented several policies over the past two decades to address them.

Figure 7.

Syllogism structure of net-zero energy building (NZEB) according to the sustainability concept.

Efficiency in the building sector is critical for economic growth and energy security. India has made remarkable strides in energy efficiency since the passage of the historic energy conservation (EC) Act in 2001. To promote modern building materials and construction techniques, a unified national building code (NBC) was launched in 2005 and revised in 2015.⁵⁶ Additionally, to achieve energy efficiency in the building sector Bureau of Energy Efficiency (BEE) launched the EC building code (ECBC) in 2007 followed by an updated version in June 2017.⁵⁷ Figure 8 shows the various initiatives taken by the Indian government to achieve energy efficiency.⁵⁸

Figure 8.

India's energy efficiency initiatives in the building sector.

Moreover, India has collaborated with international organizations to promote green energy and energy efficiency. Initiatives such as the Partnership to Advance Clean Energy (PACE) between India and the United States aimed to focus on energy efficiency, RE research, ECBC implementation, and clean energy financing. The Indo-Swiss BEEP is a collaborative effort taken by the Federal Department of Foreign Affairs of the Swiss Confederation (FDFA) and the Ministry of Power (MoP) of the Government of India. The project aimed to assist building designers in developing structures that are more energy-efficient through the creation of novel techniques, regulations, and instruments. Recently, collaboration has been made by India with the USA to establish the Centre for Building Energy Research and Development (CBERD). The primary aim of the center is to create a five-year action plan to facilitate green energy production and promote EC. With funding support from the Department of Science and Technology (India) and the UK Research Council and the Newton Bhabha Fund, India and the UK have taken an initiative to reduce the energy demand for built structures. This initiative caters to four categories: reducing residential building energy demand in India, implementing the Integrated Urban Model for Built Environment Energy Research (iNUMBER), achieving Zero Peak Energy Demand for India (ZED-I), and addressing Community Scale Energy Demand Reduction in India (CEDRI).^59–62 In November 2021, during the 26th UN climate change conference (COP 26), India proposed its agenda to achieve net-zero emissions by 2070, demonstrating its commitment to combating climate change.

India remains progressive and one of the front runners in achieving energy efficiency through various initiatives and programs for buildings such as the PAT scheme, standard and labeling (S&L), Unnat Jyoti by affordable LEDs for all, BEE star rating, EESL building energy-efficiency program, nearly ZEB, Shunya labeling for NZEB. It was found that through the implementation of programs, 249.88 BU of annual electricity was saved which is equivalent to 202.41 million tons of carbon emission. Around 365 buildings were in compliance with the ECBC by 2021–2022 and saved 79.19 MU of electricity (equivalent to 1.4 mt CO₂ emission). Under the national green rating system “GRIHA” 61 existing buildings are compliance which contributed to achieving 88.20 MU of electrical energy saving. Through the star rating of the commercial building program, 264 buildings are certified. The Shunya labeling program for net ZEB of nearly NZEB was launched in 2021. The Eco-Niwas Samhita (ENS) part-1 was launched in 2018 to achieve energy efficiency in residential buildings and their second version was launched in 2022. Through the implementation of ENS 2.42 MU of energy was saved which is equivalent to 0.00021 MT of carbon emission. Labeling program of residential building estimated potential to reduce energy demand by 388 BU. Under the PAT scheme of phases, 4, 5, and 6 total of 55% of energy was saved which is equivalent to 6514 tons of oil combustion.⁵⁸ However, despite all these initiatives, India needs to take more stringent action to achieve the net zero status. Therefore, more robust strategies and actions are needed to address the current energy efficiency challenges and achieve net-zero status by 2070.

Methodology

NZEBs are experiencing rapid growth in developed nations while encountering various challenges and barriers in developing nations.⁶³ In the past research, it has been illustrated that the EPI of the commercial buildings in India falls in the range of 86–179 kWh/m² which is much higher than that of the USA and China.⁶⁴ Therefore, there is a substantial gap between construction practices, efficient materials, significant technologies, and modeling approaches among the nations. Consequently, an immediate review is required of NZEB for economic development, reducing environmental impact, and climate change.

The methodology of this proposed review consists of two phases. In the first phase, energy data and design strategies of 14 NZEBs/energy-efficient buildings in the tropical climate of the most developed nation, the USA, and the most developing countries, China and India have been collected. The selection criterion for RCSs and their performance assessment is shown in Figure 9 and elaborated in the “Selection of reviewed case studies and their assessment” section. A comparative assessment has been conducted with their respective countries’ energy-efficiency standards, namely ASHRAE 90.1.2010, GB50189-2015, and ECBC 2017 for the USA, China, and India, respectively. Finally, the inferences have been drawn from the imbalances in the technological and materials research. It has also been observed that the implementation and enforcement of energy-efficiency codes in the application of NZEB in India are more resilient than in the USA and China, which pose barriers to the development of NZEB. In the second phase, 30 NZEB case studies from India, South Asia, and other countries have been investigated based on the implementation of active and passive features and their impact on the EPI. The key design factors for NZEB development have also been discussed briefly. The steps for the selection of reviewed case studies and their assessment are as follows:

Figure 9.

Methodology of case studies selection, assessment, and analysis criteria.

Selection of reviewed case studies and their assessment

Reviewed case studies have been selected based on inclusion and exclusion criteria. Web of science, Scopus, google scholar database, government-published reports, and manuals are used with the different keywords pertaining to NZEB for searching the case studies.

The selected studies have been filtered out based on climatic conditions (tropical/cooling dominant) and the availability of simulated or metered energy data.

The buildings in the selected case studies have already been assessed and evaluated according to one of the existing rating systems and energy-efficiency standards.

General criteria such as construction year, build-up area, orientation, aspect ratio, floor-to-floor height, and building plan to obtain insight regarding selected case studies have been taken into account which are listed in Table 3.

Further, various passive design strategies including wall, roof, glazing configuration, and their thermophysical properties, natural ventilation, and shading systems have been identified. Their critical investigation is illustrated in Table 4. Active design strategies including lighting, HVAC systems, RE generation, and their effectiveness on building performance are listed in Table 5.

Finally, inferences have been drawn from the critical assessment of case studies to identify suitable design measures and technologies to enhance the building energy model and make it net zero.

The energy efficiency of the building has been assessed by considering the annual EPI which is determined by dividing the total energy consumed in the building, measured in kilowatt-hours (kWh), by its gross floor area over the course of one year.

Analysis of reviewed case studies

Building envelop assessment

An efficient envelope design can reduce 70% of the building's energy demand. External walls are responsible for enhancing the thermal and acoustic comfort of occupants. Thermal performance plays a significant role in building performance. An average of 30% of energy consumption is due to heat losses through the external wall.^10,83 In reviewed case studies, the authors calculated that the average U-value of the wall in the tropical climate of India is 1.04 W/m²K which is much higher than the ECBC 2017 energy-efficiency standard of 0.40 W/m²K. Similarly, the average wall U-value of buildings in China that experience hot summers and cold winters is 0.416 W/m²K which is lower than the energy-efficiency standard for commercial buildings, GB50189-2015 of China, that is, 1.5 W/m²K. In the same manner, the average wall U-value of the USA buildings, that experience a hot humid climate is 0.30 W/m²K which is lower than the ASHRAE 90.1 2010 requirement of 0.52 W/m²K.

Table 3.

Hierarchy of case studies general details, listed in chronological order.

S. No.	Reference	Building name	Climate zone	Construction year	Building typology	Location	Build-up area (m²)	No. of floors	Orientation	Aspect ratio	Floor-to-floor height	Air-conditioned space (%)	Building plan	Significance
India
Case-1	Khosla⁶⁵ and Volvo-Eicher Corporate Headquarters in Gurgaon, India by Romi Khosla Design Studios⁶⁶	VECH	Composite	2012	Office	Gurugram	9972	6	NE-SW	1:2.6	3.6	100	Open rectangle	LEED Platinum
Case-2	Chaturvedi and Sharma⁶⁷	Pinnacle Infotech	Composite	2016	Office	Jaipur	10,260	4	North	NA	3.6	75	Rectangle	LEED BD + C certified
Case-3	IGBC’s Initiatives for Advancing Net Zero Energy Buildings: Indian Green Building Council (igbc.in)⁶⁸	Skyview corporate park	Composite	2015	Office	Gurugram	23,500	9	NE-SW	1.6	3.6	100	Open rectangle	LEED Platinum
Case-4	IGBC’s Initiatives for Advancing Net Zero Energy Buildings: Indian Green Building Council (igbc.in),⁶⁹ GRIHA, 2018. Case study of SBD1, Infosys Limited, Hyderabad⁷⁰	CII Green Business Center	Warm and humid	2003	Office	Hyderabad	11,148	6	NE-NW	1:1	3.6	60	Circular rectangle	LEED Platinum
Case-5	Infosys Hyderabad Building Awarded Highest LEED Rating,⁷¹ Srinivas⁷²	Infosys	Composite	2011	Office	Hyderabad	24,730	6	N-S	1:2.6	3.6	70	Open + Cellular	LEED Platinum
USA
Case-1	Regnier et al.⁷³	Kuykendall hall	Tropical hot semi-arid	2012	Office	Honolulu city	6874	4	N-E	1:1.2	3.50	82	L-shaped rectangle	ASHRAE 2013 compliance
Case-2	South b. LEED platinum energy performance case study 2010⁷⁴	Indo-way	Dry summer subtropical	2014	Office	USA	2950.5	1	NE-SW		4.5		Square, 15° of north	2017 ASHRAE technology award, net positive building
Case-3	Indio way⁷⁵	Blackstone south office	Temperate semi-arid	2006	Office	USA	3716.12	4	E-W	1.25	3.2	85	Rectangular	LEED Platinum building
Case-4	Pasunuru et al.⁷⁶	Meadowbrook	Hot and humid	2012	Office cum educational	USA	9428	2	E-W	1:1.1	3.50	NA	Rectangular	NA
China
Case-1	Sang et al.⁷⁷	Cullinan Tower	Warm and humid	NA	Commercial	China	1717	10	North	1:1.5	3.42	90	Long façade	NA
Case-2	Rick Diamond w, memberashrae⁷⁸ and Feng RDaW. Sustainability by Design How One Building in China Could Change the World⁷⁹	Shenzhen headquarter	Tropical	2009	Office building and research lab	China	18,169	12	N-S axis		3.6	97	Open rectangle	National Green Building Award (China)
Case-3	US Green Building Council⁸⁰	NA	Tropical		Office	Beijing	4025	4	NA	NA		100		Standard GB 50736-2012: compliance building
Case-4	Huang et al.⁸¹	Xixi Campus office	Hot summer and warm winter	2012	Commercial	China	7150	5	N-S	1:1.4	3.50	100	Circular	Nearly net zero
Case-5	Zhou et al.⁸²	Project, Binhai	Hot summer and warm winter	2013	Commercial building	Tianjin	3467	2	N-E	NA	3.40	100	Shape coefficient is 0.22

Table 4.

Building passive parameters assessment of India, the USA, and China case studies, listed in chronological order.

Case	Wall assembly and U value (W/m²K)	Roof assembly and U value (W/m²K)	Glass - U value (W/m²°K)	WWR (%)	SHGC/VLT	Glazing system property	Ventilation system	Shading system
India
Case-1	Cavity wall clad with tilesU value—1.1	Roof gardenU value—0.25	Double glass windowU value—2.1	80	0.697/NA	Full-length window glazing	Natural + mechanical	Recycled railway sleepers for double-curved louversShading coefficient—0.80
Case-2	Outer cladding of stone with 45 mm, plastering of 20 mm, air cavity, brick wall 230 mm, and inner plaster of 20 mmU value—1.39	High SRI tiles + concrete screed 25 mm, brickbat Coba 75 mm, cement plaster 20 mm, RCC slab 200 mm, rubber insulation 19 mmU value—1.07	Double glazed glassU value—1.58	34.88	1.13/ 66%	Double-glazed glass for the south, east, west façade andSGU for north façade	Natural + mechanical	Shading coefficient—0.78
Case-3	Cavity wallU value—1.16	Reflective insulated roofU value—0.3	Double glazed glassU value—1.8	55	0.629/ NA	Dual-pane low E-glass	Natural + mechanical	No shading
Case-4	Aerated concrete blocks and fly ash bricksU value—0.57	U value—0.294	U-value of doubleU value—1.70	NA	0.9/ NA	Double-glazed units with argon gas fillingbetween the glass panes	Natural	Fenestration maximized on the northorientation
Case-5	Fly ash-based AAC blockU value—0.36	150 mm RCC slab with insulation + cool roofU value—0.33	DGUU value—1.2	25	1.8/NA	Double-glazed units with argon gas filling	Natural + mechanical	Recessed window
USA
Case-1	Brick wall + insulation + storm roof wall louversU value—0.818	Attic roof with effective reflection insulation materialU value—0.216	Double glazing with 90% argon filledU value—1.63	25	0.388/68%	Structured coating	Natural + mixed mode	Undulating horizontal louvers and 4.2 feet fins with mechanicaladjustable shading system
Case-2	Insulated Concrete walls 150 mm thick polystyrene R-20 exterior insulationU value—0.05	Foam insulation (R-40), with cool roof coating with batt insulationU value—0.025Reflectivity—0.55	Dynamic double-glazing glassU value—0.4	100	0.09/58%	Glazing electrochromic—11%	Natural + fan control + CO₂ sensor + skylight	Solar shading
Case-3	90 mm insulation cavity wallU value—0.285	Cool/high albedo roofU value—0.024 to 0.032	U value—0.25	45	0.21/ NA	Double pane, argon-filled, and low-E glass	Energy recovery wheel + CO₂ sensor	NA
Case-4	R-28 Spray foamInsulation and concrete wallsU value—0.064	Poly isocyanurate insulation of R-40insulationU value—0.039	Low-E, triple-paneU value—0.25	85	0.32/25%	85% glazed with local shades	Natural	Horizontal adjustable shading system
China
Case-1	6 inch Concrete + no exterior finish + medium color (Abs = 0.6) + polystyrene insulationU value—0.76	6 inch Concrete + medium color (Abs = 0.6) + 1.5 inch polystyrene (R-6)U value—0.9	Double Low-E Tint 1/4 inch glass layer combined with a 1/2 inch glass layer and filled with argon gasU value—1.13	25	0.37/44%		Natural	6.5 mm Window overhang
Case-2	Insulated concrete panel with aluminum claddingU value—0.35	Roof garden (green roof) shaded with a PV canopyU—0.25	Double-panelow-EwindowsglassU value—1.99	50%	0.4/45%	Varies by orientation from 30% to 70%	Natural + mechanical	Movableexteriorshutters areused on theeast-elevationonlower floorsto controlsunlight
Case-3	External wall with 2 mm decorative coating, outer layer consist of aerated concrete block (200 mm) and a decorative board integrated with an ultrathin vacuum insulated board (25 mm)U value—0.24	U value—0.16	aluminum alloy windowU value—1.0		0.47/38%	tempered glass with a 5 mm low-emission film, 2 mm vacuum layer, 5 mm glass, 27 mm air layer, and 5 mm tempered glass	Natural + mechanical	shading coefficient—0.26
Case-4	Cavity hallow glass wall systemU value—0.58	RCC slab + reflective roof surfaceU value - 0.46	Advanced glazing system withU value—2.8		0.5/ 52%		Natural ventilation	Solar shading and blinds for glare control
Case-5	Autoclaved aerated concrete block + Rock wool boardU value—0.15	RCC + extruded polystyrene board (XPS board)U value—0.12	Double-glazed low-E glass with aluminum alloyU value—1		0.55/42%		Natural	shading coefficient—0.42

Table 5.

Building active parameters assessment of India, the USA, and China case studies, listed in chronological order.

Case	Lighting system		HVAC system		Lightning performance index (kWh/m²/year)	HVAC performance index (kWh/m²/year)	Annually energy performance index (kWh/m²/year)	Renewable energy
Case	Fixture specification	LPD(W/m²)	System type	Technical specification	Lightning performance index (kWh/m²/year)	HVAC performance index (kWh/m²/year)	Annually energy performance index (kWh/m²/year)	Renewable energy
Case-1	LEDs with motion sensors	4	Water-cooled chillerCapacity—2335 kW	COP—6Design specification—15 m²/TR	7	71	79	NA
Case-2	LED + occupancy sensor	4.9	Package VRF system	COP - 4.9 andCooling set point temperature 75 °F	6.46	29.33	97.33	Installed 100 kW
Case-2	LED + occupancy sensor	4.9	Package VRF system	COP - 4.9 andCooling set point temperature 75 °F	6.46	29.33	97.33	Generation156.96 kW
Case-3	T-5, LED fixture	9.5	High-efficiency filter of HVAC	COP—5.4 andDesign specification—13 m²/TR	16.9	79	112	NA
Case-4	T5 and CFL with daylight sensor	7.2	ARI condition	COP—4.23 andTwo chillers with 25 TR capacity	13	64	84	23.5 kW/20% of the total demand
Case-5	T5 and CFL with daylight sensor	4.8	Central,Capacity—1400 KW	COP—7	8.8	32.25	51.85	44 kWp solar panel
Case-1	Efficient LED fixtures of T5 type, Daylight dimming control, occupancy sensor	5.4	DX cooling system with natural ventilation and night dehumidification	COP—3.7EER—10.3	12.55	17.45	30	NA
Case-2	Dimmable LED + occupancy + CO₂ sensor/skylight and daylight control system	4.6	Heat pump system + MERV system	Design specification: 1200 ft.²/ton	7.3	14.5	42.6	solar PV generation—83.7 kWh/sq/year
Case-2		4.6	Heat pump system + MERV system	Design specification: 1200 ft.²/ton	7.3	14.5	42.6	500 kWh/year for hot water heating
Case-3	Occupancy and daylight sensors	8.61	Geothermal wells and heatpumps with BMS system to shut down AHU		38.39	25.76	86.50	100% load by RE
Case -4	surface-mounted LED lamp	4.2	Bipolar ventilation with 5cfm/person + Air-cooled chillers	COP—4.0Efficiency—1.21 kW/ton	8	32	85	317 kW
Case -1	Advance lighting + occupancy sensor	5.2	Combined heat and power chiller + ground source heat um GDP, and the chiller's + set point 28 °C	COP—5.0	8.12	21	29.12
Case-2	T-5, LEDfixture, SomeCFL Bulbs	0.7	Water-loop heat pump, water source heat pump		10.17	14	63	BIPV system generation = 70,000 kWh
Case-3	LED + occupancy sensor	LPD = 6	Single-effect LiBr-H₂o absorption chiller	Design specification—37 W/m²cooling capacity—35.17	8.5	23	32.5	Daily average output from PV system = 1031.43 kWh
Case -4	Daylight sensor and BMS system	5.3	GSHP + VRF	COP—5.3	8.5	54	70
Case -5	Daylight sensor and monitoring system	6.9	175 kW cooling capacity heat pump	COP—5.9	13.1	35.1	69.9

Figure 10 reveals that developed countries such as the USA's NZEBs/energy-efficient buildings have more stringent thermal integrity than other developing countries such as China and India. Increasing the thermal mass of the wall through insulation, cool/low VOC paint, cavity hollow walls, and installing green walls reduce the heat from solar radiation and enhance the thermal performance of the building.

Figure 10.

U-value of wall for India, the USA, and China.

The roof accounts for 8%–10% of total energy consumption due to heat losses through conduction and radiation.⁸⁴ Figure 11 shows that the average of the Indian RCS roof's U-value is 0.44 W/m²K which is below the ECBC standard of 0.30 W/m²K. Similarly, the average roof U-value of China and the USA RCS is 0.41 and 0.077 W/m²K, respectively, which fares much better than their standard, 0.9 W/m²K of GB50189-2015 of China and 0.272 W/m²K of ASHRAE 90.1, 2010 of the USA, respectively. After overall comparisons, it has been observed that the USA and China buildings’ roofing systems are more efficient and have higher thermal mass than Indian roofing systems.

Figure 11.

U value of roof - India, the USA, and China.

Further, glass also plays a significant impact on the building's energy load, thermal, visual, and acoustic comfort. An appropriate selection of glass enhances thermal and visual comfort by 13%–30% and 50%–85%, respectively. Also, changing the window-to-wall ratio (WWR) according to climate conditions can cut down cooling demands from 24% to 50%.^85,86 Figure 12 shows the average glass U-value of RCS in India as 1.67 W/m²K which is better than ECBC 2017 standard of 3.0 W/m²K. Similarly, China and the USA RCS average glass U-value is 1.63 and 0.58 W/m²K%, respectively, which is better than the standard value of 3.4 W/m²K, ASHRAE 90.1, 2010. Figure 13 shows the solar heat gain coefficient (SHGC) of RCS, India as 1.03 which is < 0.27, the value of ECBC standard 2017.

Figure 12.

U-value of glass for India, the USA, and China.

Figure 13.

Solar heat gain coefficient (SHGC) of glass for India, the USA, and China.

Infosys and Confederation of Indian industry (CII) green business net-zero buildings use double-glazed, low E-coated glass with 25% WWR. A higher WWR increases the cooling demand due to heat leakage and airtightness and a higher visual light transmittance (VLT) increases the daylight availability. Therefore, the optimal selection of WWR and VLT in a particular climate zone enhances comfort level, daylight availability, and indoor air quality (IAQ). According to ECBC 2017, an average of 40% WWR and 0.27 VLT are required for energy-efficient built structures to maintain a comfortable indoor environment.

Energy-efficient measures

Electrical lighting appliances consume an average of 15% of the building's energy.⁸⁷ Lighting power density (LPD) of RCS in India is 6.6 W/m² which is not adequate when compared to China and USA buildings having LPD values of 5.6 and 3.9 W/m², respectively. Further, cooling systems design is more dominant in tropical climates and it consumes 50%–60% of the building's operational energy. Figure 12 shows that the HVAC EPI of the RCS of the tropical climate of India is 55.2 kWh/m²/year which is much higher than that of the USA and China RCS of hot-humid climate having EPI of 22.50 and 30.2 kWh/m²/year, respectively. The average air conditioning, coefficient of performance (COP) of RCS in India and China is 5.38 and 4.9, respectively, that is, equivalent to the ECBC 2017 standard. On a similar note, cooling dominant zones in the USA have an average RCS HVAC systems COP of 3.42 which is much better in comparison to India's ECBC standard. Currently, variable frequency drives for automatic control systems and bipolar ionization systems are used with the HVAC systems. Thus, the building lighting and cooling energy demand have a significant impact on the building's annual performance index. Figure 14 illustrates that Indian RCS of tropical climate has an annual EPI of 84.33 kWh/m²/year which is much higher than that of the USA and China buildings having EPI values of 61.02 and 52.88 kWh/m²/year, respectively.

Figure 14.

Lighting performance index, cooling and heating performance index, and annual energy performance index for India, the USA, and China.

Moreover, geothermal energy from ground-source heat pumps (GSHPs) is commonly used in NZEB for cooling and heating. It has higher COP, the least pollution, and lower maintenance costs. Most of the case study buildings have the provision of natural ventilation through the atrium, circular courtyard, and a solar chimney that reduces cooling demands and enhances thermal comfort. Infosys building has a passive radiant mechanical cooling system with an efficient variable air volume (VAV) that reduces HVAC consumption. The skyview park and pinnacle InfoTech buildings are equipped with mechanically ventilated systems to enhance thermal comfort. The occupant behavior also plays a vital role in reducing heating and cooling energy demand. The results of this analysis draw focus to a constraint in India's simulation and computational methods, which hinder their ability to guide decisions towards attaining energy efficiency and optimal building performance during the initial design phase. Despite this limitation, simulation and optimization strategies play a pivotal role in shaping decisions regarding NZEB design.²⁰ These methods effectively tackle intricate architectural challenges, encompassing passive parameters in tandem with energy-efficient strategies and the incorporation of RE sources. Additionally, it provides the optimal trade-off solution by computing an iterative relationship of building performance objectives over the various building decision variables.⁸⁸

Application of building performance assessment tool

Building simulation tools offer potential solutions for both new constructions and necessary interventions in existing buildings to enhance energy efficiency. The integration of algorithmic optimization with simulation tools is the growing trend in building design research to map out the decision support for maintaining a comfortable built environment, conserving energy and environment, and reducing building costs.⁸⁹ This approach proves valuable in selecting and refining control strategies and HVAC designs. Furthermore, it proposes control strategies during building operations based on model predictive control strategies. Bano and Sehgal⁹⁰ investigated the performance of existing public buildings situated in India's tropical climate using the Design Builder tool. This research evaluates the potential of various influential parameters such as orientation, geometry, envelope properties, thermal mass, lighting, and HVAC and their significant impact on the energy performance of government and public buildings. Gunjan et al. (2020) explored the energy performance benchmarks of existing high-rise residential buildings in the hot and humid climatic zone using simulation techniques. This work focused on the implementation of building envelope features which are mentioned in ENS and ECBCs, through the EnergyPlus tool. It reveals that implementation of the computational tool at the early design stage can reduce the cooling energy demand by 7%–37%.⁹¹ Similarly, Bano et al. (2020) analyzed the existing NZEB (IPB, New Delhi; AUB Panchkula Hariyana; PTM Malaysia) features including building layout and planning, passive designs, active measures and RE technologies and their iterative impact on daylight, thermal, thermal, and energy performances. Consequently, all suitable features were applied to a reference building model namely “Skyview Cooperative Park” which had an initial EPI of 111.3 kWh. The conclusion illustrates that the simulation tool provides the decision support to reduce the energy demand by 6.38% through site planning, followed by 12.31%, and 52.03% through envelope improvement, and by lighting, HVAC, and utilizing natural ventilation. Finally, overall, 63.07% saving is achieved long with achieves the net-zero status. The case studies and simulation results suggest that NZEB design requires ∼ 34–44 m² of floor area and 1 kW of PV panel power output.⁹² Rajesh et al. (2015) identified the energy-saving potential through the modeling and simulation of hotel building buildings in the tropical climate of India. This study utilized the eQuest tool to assess the impact of envelope design and advanced energy measures on energy consumption and revealed potential savings of 53%–61% at the early design stage which led to net-zero status.⁹³ Similarly, Ankur et al. (2012) found that building simulation tool guide for retrofitting of buildings and helps to suggest 17%−42% energy saving.⁹⁴ Mayank et al. (2018) developed a reference building model by optimizing various samples of existing buildings.⁹⁵

Assessment of 30 NZEBs

This section demonstrates the assessment of 30 NZEB studies in which 10 from India, 11 from South Asian countries, and nine from other countries are included. The concept of an NZEB mainly focuses on three factors which are building sufficiency, building efficiency, and RESs.⁹⁶ Figure 15 addresses the paths for NZEB during the design stage. Energy sufficiency emphasizes climate-adaptive design and building passive features such as natural ventilation, daylight, building geometry, advanced envelope, and insulation that do not require operational energy in execution. Energy efficiency includes energy-efficient technologies such as appliances, HVAC systems, artificial lighting, and heat storage systems that can reduce RE demand. RE systems to fulfill the building's operational demand.⁹⁷

Figure 15.

Path of net-zero energy building design.⁹⁶

The authors investigated thirty NZEBs based on implemented active and passive design strategies and their impact on building energy performance. Also, identified and illustrated different passive design strategies and technological options such as lighting and HVAC systems that can reduce energy demand. Moreover, state-of-the-art passive design features such as building envelope, advanced glazing, shading, and thermal mass are defined to reduce the cooling demand and enhance occupant productivity that can contribute to climate-adaptive NZEB design and the RE supply options that play a significant role in achieving the carbon neutral environment. Table 6 addresses the general details of 30 investigated high-performance NZEB. It reveals that most of the buildings are commercial and certified by the region-specific net-zero building norms. Moreover, all NZEB studies come under hot humid, and tropical (cooling dominant) climates. Except for one building (Malankara Tea Plantation), all NZEBs have grid connectivity to balance the demand and generation side. The active and passive design parameters that are considered for the evaluation of NZEB are illustrated in Table 7. Passive design is divided into eight groups which are natural ventilation, site vegetation, advanced glazing, thermal mass, advanced envelope, orientation, shading, and daylight. Active design technologies include mechanical ventilation, efficient lighting, efficient appliances, advanced lighting control, domestic hot water, radiant cooling and heating, and evaporative cooling.

Table 6.

General details of reviewed NZEB of India, South Asian countries, and other region countries, listed in chronological order.^98–101

S. No.	Building name	Location	Area (m²)	Building typology	Completion year	Grid connectivity	Significance	Climate zone	Koppen climate	EPI (kWh/m²/yr)
1	SIERRA's Facility	Coimbatore,Tamil Nadu, India	2322	Office	2017	Y	NA	Tropical savanna	Aw	56
2	Lodsi Community Project For Forest	Lodsi,Uttarakhand, India	929	Office	2019	Y	NA	Hot-summer Mediterranean	Csa	35
3	Unnati	Greater Noida, India	3740	Office	2018	Y	Platinum (LEED v4 BD + C: NC rating)	Hot semi-arid	BSh	60
4	Infosys Pocharam Campus	Hyderabad, Telangana, India	27,870	Office	NA	Y	LEED Platinum andGRIHA 5 Star	Hot semi-arid	BSh	75
5	Godrej Plant 13 Annexe	Mumbai, Maharashtra, India	24,443	Multipurpose	2008	Y	LEED platinum (IGBC) andBEE 5-star rating	Tropical savanna	Aw	75
6	CEPT, a living laboratory	Ahmedabad, Gujarat, India	498	Office and Educational	NA	Y	NA	Hot semi-arid	BSh	58
7	Indira Paryavaran Bhawan, MoEF	New Delhi, India	9565	Office	2013	Y	GRIHA 5 Star andLEED Platinum	Hot semi-arid	BSh	44
8	Akshay Urja Bhawan,	Panchkula, Haryana, India	5100	Office (public)	2012	Y	GRIHA 5 Star	Humid subtropical	Cwa	30
9	Eco Commercial Building (ECB) Bayer Material Science	Greater Noida, Uttar Pradesh, India	891	Office (private)	NA	Y	NA	Hot semi-arid	BSh	72
10	Malankara Tea Plantation	Kottayam, Kerala, India	—	Office	NA	N		Tropical monsoon	Am	90
11	Shenzhen Institute of Building Research (IBR) Headquarters	Shenzhen, China	18,169	Office and Research lab	2009	Y	LEED Platinum	Humid subtropical	Cfa	63
12	Arthaland Century Pacific Tower	Metro Manila, Philippines	38,714	Office	2017	Y	LEED Platinum and BERDE 5-stars	Tropical savanna	Aw	131.97
13	CIC Zero Carbon Park (CIC ZCP)	Hong Kong, China	14,700	Multipurpose	2012	Y	NA	Humid subtropical	Cfa	102.87
14	Brandix – Batticaloa Factory	Batticaloa, Srilanka	18,652.45	Manufacturing Facility	NA	Y	Platinum (LEED) andISO 50001 Energy Management	Tropical monsoon	Am	147
15	Bayalpata Hospital	Achham, Nepal	4225	Medical Complex	2019	Y	NA	Temperate	Cwb	9.68
16	Pringapus 6 – PT Ungaran Sari garments	Semarang, Indonesia	17,424.5	Manufacturing Facility	2018	Y	LEED	Tropical rainforest	Af	103
17	Mobil House	Dhaka, Bangladesh	6672.80	Office	2019	Y	LEED Platinum	Tropical savanna	Aw	106
18	Star Garment Innovation Centre	Colombo, Sri Lanka	3675	Factory/Industrial	2018	Y	Passive House (PH)	Tropical rainforest	Af	164
19	BCA Zero Energy Building	Braddell Road Singapore	4500	Office	NA	Y	NA	Tropical rainforest	Af	23
20	School of Design and Environment	NUS, Singapore	8514	Academic	NA	Y	NA	Tropical rainforest	Af	58
21	Diamond Building	Putrajaya, Malaysia	158	Office	2010	Y	Platinum (Green Building Index)	Tropical rainforest	Af	85
22	PTM ZEO	Selangor, Malaysia	4000	Office	2007	Y	Green building index	Tropical rainforest	Af	35–40
23	Omega Center For Sustainable Living	Rhinebeck, NY	6250	Recreational center	2009		LEED Platinum	Humid subtropical	Cfa	231
24	Maison Hanau	France	180	Residential	NA	Y	NA	Temperate oceanic	Cfb	42
25	City Square Condominium Community	California, USA	44 units: 173–202 m² per unit	Housing	2019	Y	Energy star 3.2	Dry-summer subtropical	Csa	4 kW per dwelling unit
26	Phillips Center For Sustainable Landscapes	Pittsburg, USA	24,350	Research/Educational	2013	Y	LEED Platinum, Platinum (SITE)BREEAM andFitwel 3 star	Humid subtropical	Cfa	204
27	Wayne N. Aspinall Federal Building and U.S. Courthouse	Colorado, USA	3901.91	Public building	1918; Retrofitted 2010	Y	LEED Platinum	Humid subtropical	Cfa	231
28	Powerhouse Kjorbo	Norway	5200	Renovated office building	Renovated 2014	Y	BREEAM NOR Outstanding		Dfb	28
29	Horizont Building Strassen	Luxembourg	3200	Office		Y	HQE	Temperate oceanic	Cfb	76
30	NREL Research Support Facility Golden	Colorado, USA	20624	Office/research facility	NA	Y	NA	Humid subtropical	Cfa	110

Table 7.

Evaluation of 32 NZEBs based on passive and active measures, listed in chronological order.

Building Name	Passive design features									Active design features
Building Name	Natural ventilation	Site vegetation	Advance glazing	Thermal mass	Advance envelop	Orientation- floor plan	Shading	Daylight	Mechanical ventilation	Efficient lighting	Efficient appliance	Advanced lighting control	Hot water recovers	Radiant cooling/ heating	Fan/ evaporative cooling	Conventional all-air system
SIERRA's Facility	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓				✓
Lodsi Community Project for Forest	✓			✓	✓	✓	✓	✓	✓							✓
Unnati	✓	✓	✓		✓	✓	✓	✓	✓	✓	✓	✓		✓		✓
Infosys Pocharam Campus	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓		✓
Godrej Plant 13 Annexe	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓				✓
CEPT, a living laboratory	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓			✓	✓
Indira Paryavaran Bhawan, MoEF	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓			✓	✓
Akshay Urja Bhawan,	✓		✓	✓	✓	✓	✓	✓	✓	✓	✓				✓	✓
Eco Commercial Building (ECB) Bayer Material Science	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓	✓
Malankara Tea Plantation	✓	✓		✓					✓							✓
Shenzhen Institute of Building Research (IBR) headquarters	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓
Arthaland Century Pacific Tower	✓		✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓
CIC Zero Carbon Park (CIC ZCP)	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓
Brandix – Batticaloa Factory			✓		✓	✓		✓	✓	✓	✓	✓
Bayalpata Hospital	✓			✓	✓	✓	✓	✓	✓
Pringapus 6 – PT Ungaran Sari Garments	✓	✓		✓		✓	✓	✓		✓
Mobil House		✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
Star Garment Innovation Centre			✓	✓	✓	✓	✓	✓	✓	✓	✓
BCA Zero Energy Building	✓		✓		✓	✓	✓	✓	✓	✓	✓	✓			✓	✓
School of Design and Environment	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓			✓
Diamond Building	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
PTM ZEO	✓		✓	✓	✓	✓	✓	✓	✓	✓	✓			✓	✓
Omega Center for Sustainable Living	✓	✓		✓		✓	✓	✓	✓	✓	✓	✓		✓
Maison Hanau
City Square Condominium Community	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓ ✓	✓	✓
Phillips Center for Sustainable Landscapes	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓
Wayne N. Aspinall Federal Building and US Courthouse			✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓
Powerhouse Kjorbo	✓		✓		✓	✓	✓	✓	✓	✓	✓	✓		✓
Horizont Building Strassen	✓		✓	✓		✓	✓	✓	✓	✓	✓	✓	✓	✓
NREL Research Support Facility Golden			✓	✓	✓	✓	✓	✓	✓	✓	✓	✓		✓

Technological options and strategies for NZEB

Climate-adaptive architectural design and passive features increase thermal and visual comfort while also reducing the building energy demand. The passive techniques emphasize on solar heat protection, heat modulation, and heat extraction parameters of the building configuration which are shown in Figure 16(a) to (c), respectively.^96,102

Figure 16.

(a) Heat protection passive technique, (b) heat modulation passive technique, and (c) heat extraction passive technique.

Tropical climate NZEBs adopted green vegetation, water surfaces, advanced glazing, and shading systems for heat protection. Heat modulation systems include natural ventilation, phase change materials (PCMs), and thermal mass. This passive heat modulation technique emphasizes restraining the heat inside the building due to air leakage and solar heat through building walls, roofs, and glass by conduction, convection, and radiation. The heat extraction techniques include the free cooling system installed in the building. It includes convection cooling systems (wind-driven ventilation, Trombe wall, solar chimney, and stuck ventilation), radiative cooling systems, and direct and indirect evaporative cooling systems. The active technique focuses on enhancing occupant comfort. It consists of artificial lighting, air-conditioning, mechanical ventilation, appliances, plug-load systems, hot water systems, monitoring, and control systems. The authors identified some passive and active strategies for the assessment of 30 NZEBs and Figure 17 illustrates the number of times each strategy is used.

Figure 17.

Number of active and passive design strategies used in net-zero case studies.

Passive techniques

Passive techniques focus on increasing energy efficiency through building geometry. The building geometry includes orientation, building form, shape, shape proportion, volume, and aspect ratio. Moreover, these techniques also focus on the orientation of the building with respect to the sun's movement around the building. The heat inside the building can be reduced through optimization of building orientation. Natural ventilation plays a significant role in reducing the cooling demand and it also improves the thermal comfort of the occupants. Most NZEBs in India incorporate an atrium and courtyard for natural ventilation to circulate fresh air, reduce heat, and improve indoor air quality.

Building façade design

This focuses on creating an optimal envelope design for the building. Envelope design consists of building wall, roof, floor, ceiling, and foundation system. There are several wall strategies used in NZEBs to reduce the solar heat gain of the building which are Trombe walls, autoclaved aerated concrete (AAC) walls, double skin (cavity) walls, PCM walls, and green wall systems. Some NZEBs reviewed in this article used green wall and roof systems to reduce heat gain and improve aesthetics. In general, the different types of roofing systems used in NZEB design are the high roof, double roof, valuated roof, dome roof, ventilated, micro-ventilated roofing system, and cool roof. For cool roofing, high albedo insulation material coating is used over the roof surface and outdoor pavements. Two types of insulation used in roofing include reflective type (aluminum foil) and resistive type (polyurethane). Reflective solar radiation roofing system reduces the cooling load by 7%–57% depending on the climatic conditions and the city's heat island effect.⁷⁸ Moreover, insulation materials have the capability to enhance the thermal characteristics of the building envelope. These materials are categorized into various groups based on the specific properties of the insulation compound such as organic insulation (sheep wool, cotton wool, cellulose, polystyrene, phenol, melamine, and cork), inorganic insulation (glass wool, stone wool, and foam), combined insulation (siliconized calcium, gypsum, and wood wool), and special insulation (transparent and dynamic).

Glazing system

Window glazing is responsible for 60% of heat generation inside the building space.¹⁰³ Appropriate selection of the glazing material can prevent solar heat gain. The selection of the glazing system includes thermophysical characteristics such as U-value, SHGC, visual light transmission, and light-to-solar gain. In general, there are two types of glazing systems which are static and dynamic glazing systems. Static glazing has constant thermal and optical properties and it includes tinted glazing, low-emittance glazing, anti-reflective coating glazing, aerogel glazing, and inherent gas-filled double glazing. Dynamic glazing has inherent optical switching technology and it includes thermochromic, electrochromic, PV electrochromic, gasochromic, and liquid crystal glazing systems.

Thermal mass

Thermal mass refers to a material's capacity to function as a thermal barrier by absorbing, storing, and releasing heat. High-density materials, such as concrete and PCMs possess greater thermal mass. However, higher thermal mass does not provide the guarantee of thermal comfort and energy consumption because such materials demand more time to heat/cool given that the building is in a steady-state condition. PCM reduces the temperature fluctuation of building envelope configuration and provides better thermal comfort. Twenty-five of the reviewed NZEBs used the concept of thermal mass for energy efficiency. Out of these, 17 NZEBs used PCM to decrease the temperature difference between day and night.

Shading system

Incorporating the building shading system's position angle according to the sun's movement reduces the peak heat gain, and cooling energy demand and provides glare-free natural daylight. Depending on the working mechanisms, the shading devices are categorized as fixed, manually adjustable, and dynamic-controlled shading systems. Choosing the right active shading system in tropical climates can reduce the cooling demand by 12%–15%.

Active design technologies

Lighting system

Efficient use of lighting and control systems can reduce the building's operational energy demand. According to ECBC, artificial lighting control such as occupancy and illuminance modulation sensors are mandatory provisions for energy-efficient and net-zero commercial buildings. The motive of the controlling sensor is to optimize maximum daylight availability, reduce energy demand, and improve occupants’ visual and thermal comfort. The selection of lighting fixtures and designing for NZEBs should follow these principles:

Fixture design and position: Artificial light should provide a sufficient amount of light on the horizontal floor at work plane height (0.8 m) so that human activities and tasks can be performed efficiently and comfortably.¹⁰⁴

Efficient source of lighting: The fixtures should have higher illuminance, higher efficacy, low consumption, and low cost. The ECBC recommends the lowest lighting power density for lighting design. It can be calculated by the space function method and building area method.

Smart controlling: ECBC says that 90% of interior lighting should be equipped with an automatic controlling system for building space larger than 300 m².

HVAC system

NZEBs located in tropical climates witnessed higher cooling demands. Most of the HVAC systems are conventional all-air, radiant, and evaporative cooling systems used in the buildings as depicted in Table 7. Conventional all-air systems use air as a medium for meeting both ventilation and heat transfer.¹⁰⁵ Radiant cooling systems are the most efficient cooling system and alternative to conventional all-sir systems. They enhance thermal comfort and reduce 10%–40% of power consumption, unlike other active cooling systems.¹⁰⁶ This review illustrates that 14 reviewed case studies used radiant cooling systems and others 10 and eight buildings employed conventional all-air and evaporative cooling systems, respectively. In India, most of the buildings have conventional all-air systems aligned with water-cooled chillers for cooling. In hot humid climates, radiant cooling of the NZEBs becomes expensive in terms of energy consumption due to high moisture and latent heat in outdoor air. Therefore, dehumidification processes are required to get fresh air. This is achieved using humidity and temperature control methods such as deep multi-row cooling coils and energy recovery wheels. There are a few examples of commercial buildings in India that have radiant cooling systems namely Infosys Pocharam Campus, Unnati, and Eco commercial buildings, as mentioned in Table 7. On the other hand, evaporative cooling is most popular in conventional and residential buildings. It has a higher potential for heat rejection than other active cooling systems. Different available cooling strategies are direct and indirect evaporative cooling, ground-coupled, heat recovery, chilled ceiling, desiccant cooling, ejector cooling, and variable refrigerant flow. The efficiency of the cooling system depends on the COP. Increasing the COP can reduce cooling energy demand by 15%–58%.

RE production

Installation of RE systems to attain operational energy (heating, cooling, and lighting) is a promising method of achieving net-zero. Many NZEBs use rooftop solar photovoltaic (PV) systems for this purpose. However, the performance of PV panels is affected by the environmental conditions, maintenance, cleaning, panel resistance, system size, and degradation factor. Since, high-rise buildings have a limited amount of roof space and therefore, to fulfill the demand, intelligent hybrid systems and building integrated systems are used. During summer seasons, PV panels attain high temperatures that reduce the PV efficiency and increase the heat gain of the building. To tackle this, the newly developed NZEBs use natural ventilation and a double-skin façade to reduce the heat gain behind the PV panel. Furthermore, hybrid PV thermal (PV/T) systems are the most popular kind of technology employed to reduce heat gain. More commonly, the flat plate building-integrated PV/T (BIPV/T) and concentrating BIPV/T systems are used in NZEBs.

Conclusion and policy recommendations

This section illustrates the effectiveness of design strategies on the performance of NZEBs. Furthermore, it also summarizes the challenges in materials, technologies research, and policy implementation in real construction practices compared to other nations. Finally, it concludes with policy recommendations for NZEB developments in India as depicted in Figure 18.

Figure 18.

Hierarchy of review outcomes.

In summary, this review critically investigated 44 NZEB/energy-efficient buildings and demonstrated that the adoption of archetype passive design interventions and advanced technologies can lead to energy savings. An analysis of this research found that NZEB can be achieved by mainly in three pathways: active, passive, and RE. The first way emphasizes the reduction of building energy load by passive techniques such as natural ventilation, daylight, building envelope, smart glazing, and thermal mass to ensure meeting the actual performance goal. The second strategy relies on active parameters such as efficient light systems, HVAC, plug load, and smart monitoring and control systems that contribute to meeting the required load using less energy. With these two strategies, the building becomes low energy demand, and then the third strategy is required to fulfill the energy demand, which is focused on the installation of RESs such as solar PV, biomass, and geothermal to achieve net-zero status. Through extensive analysis, it has been found that NZEBs in the tropical climates of the USA and China tend to have measures that are more stringent than the country's energy standards. Therefore, there are substantial gaps in the adoption, implementation, and enforcement of energy-efficiency codes and standards in India. Furthermore, it has been observed that the average annual EPI of Indian tropical climate buildings is 84.33 kWh/m²/year which is significantly higher than the cooling dominant buildings in the USA and China, which have EPIs of 61.02 and 52.88 kWh/m²/year, respectively. This reveals that technological upgradations and industrial innovations are required compared to other developed countries. Moreover, in the “Definitions and India’s initiatives towards NZEB” section, the authors discussed various passive cooling techniques that have the potential to reduce cooling demand but in real construction practices, they are not implemented. Thus, there is an ample research gap on how passive techniques can integrate with the building design processes and energy-efficiency standards. Finally, there is a lack of an extensive framework to distinguish NZEB requirements and especially assessment of performance level, energy uses models, and generation of RE.

Policy recommendations

India is required to adopt a pluralistic and fundamental approach at the policy level to achieve the country's net-zero targets by 2070. The previous section demonstrates that various initiatives for energy-efficiency have been taken by the country for sustainable development, which is the evidence for potential and opportunities of the NZEB development in India. Moreover, this review discussed that there are still hindrances or challenges in the development of NZEB/energy-efficient buildings in the country compared to other developed nations. These challenges can be at the research and innovation of materials and technological scale, lack of policies, standards, building codes, and public awareness levels. Based on this, the main recommendations are as follows:

Stringent building codes, adoption, implementation, and enforcement of building energy codes, and their upgradation are the leading drivers to ensure the development of NZEB. Countrywide energy standards and building laws play a vital role in the adoption of smart technologies, building innovations, and research. In this review, a strong correlation has been found between envelope performance and the USA and China's energy-efficiency standards. It illustrates that the USA and China's NZEB/energy-efficient building envelope thermophysical properties are very close and slightly better than their country's energy-efficiency standards. Thus, setting up stringent building codes and standards would help the adoption of social scale development of NZEB or advanced envelope technologies. For example, the inspiration is taken from France, where the Ministry of Environment Energy and Sea developed an act of energy transition for green growth in 2015, which states that new construction should be energy-positive by 2020. In the same manner, the California Public Utilities Commission (CPUC) launched a NZE action plan in 2015, which focused on the fact that all new residential and commercial construction will be net zero by 2020 and 2030, respectively. The Directive on Energy Performance of Building (EPBD) proposed the ZEBRA-2020 program, which states that all new construction will be nearly net zero by 2020. British Columbia Energy Step Code Council of Canada states that new buildings must be ready to NZE by 2032.

Further, the continuous upgrading of building energy codes to incorporate more competitive energy performance requirements can lead to NZE development. In conclusion, to achieve the net-zero goal by 2070, the Indian government is required to develop a net-zero action plan, and its implementation is essential at the local level.

Moreover, India should constitute an inter-ministerial coordination mechanism and develop a unified policy and national programme to promote NZEB and encourage architects, consultants, builders, and other stakeholders.

Advance building technology and energy monitoring systems, application, and optimization of advanced building technologies (efficient lighting, HVAC, and energy monitoring), can ensure energy savings. Integrating smart energy monitoring and analytics systems provides real-time data on energy consumption patterns and load distribution. This could encourage users to develop sophisticated energy-saving strategies.

There is a lack of technological innovations and inadequate energy monitoring and analyst methods compared to other developed nations’ standards and guidelines. Thus, enforcing research in technology development, optimization, and upgrading energy monitoring and analytics technologies will ensure the integral development potential of NZEB.

Incentives policies for RE generation, economic measures, and policy stimuli are the principal drivers for the development of NZEB/energy-efficient buildings. The high upfront costs of installation for RE generation are the biggest challenge in developing nations. Thus, the government should take the initiative and strengthen the national-level incentive policies, financial subsidies, and additional floor-to-area ratio (FAR) to compensate for the global cost of building. It does not just help stakeholders but also enhances occupant productivity, comfort, and energy savings. Furthermore, it provides awareness of the future development of NZEB. For example, some developed countries, such as the USA, Germany, Italy, and Japan offer tax rebates and financial subsidies to promote low GHG emissions measures and on-site RE generation.

Limitations and future research

This review still has certain limitations, and further research is needed. As discussed above, the concept of NZEBs is still a relatively new concept in developing countries, yet it holds significant importance for sustainable economic development. In this article, only 44 case studies of tropical climates are discussed, and not all of them possess comprehensive design and performance data. Furthermore, due to the lack of data, the correlation and multicollinearity between envelope components, passive design strategies, technology, and energy performance index have not been explored. Therefore, it is necessary to document the best practices of NZEBs in the future and improve data transparency. Also, monitoring the operational behavior of buildings using an energy model would provide insights into the effectiveness of advanced passive and active design strategies during the operational phase. Further, compiling data on installed design, performance, and cost would enhance the credibility and persuasiveness of case studies when shared with the public. This is particularly important in emerging economies with tropical climates, as documenting best practices would not only showcase the effectiveness of NZEBs, but also help in overcoming barriers among stakeholders. In future research, in-depth analysis can be conducted with a larger sample size and data set.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article

ORCID iD

Pushpendra Kumar Chaturvedi

References

Qiu

. A comparison of building energy codes and policies in the USA, Germany, and China: progress toward the net-zero building goal in three countries. Clean Technol Environ Policy 2019; 21: 291–305.

Energy Agency I. Review 2021 Assessing the effects of economic recoveries on global energy demand and CO2 emissions in 2021 Global Energy [Internet]. 2021. Available from: www.iea.org/t&c/.

Omrany

Chang

Soebarto

, et al. A bibliometric review of net zero energy building research 1995–2022. Energy Build 2022: 111996.

EIA. Energy Information Administration (EIA). International Energy Outlook 2017 Overview. (2017). Available on: https://www.eia.gov/outlooks/ieo/pdf/0484(2017).pdf. Accessed: [15/11/2021].

Ürge-Vorsatz

Khosla

Bernhardt

, et al. Advances toward a net-zero global building sector. Annu Rev Environ Resour 2020; 45: 227–269.

Cielo

Subiantoro

. Net zero energy buildings in New Zealand: challenges and potentials reviewed against legislative, climatic, technological, and economic factors. J Build Eng 2021; 44: 102970.

Manu

Shukla

Rawal

, et al. Field studies of thermal comfort across multiple climate zones for the subcontinent: India model for adaptive comfort (IMAC). Build Environ 2016; 98: 55–70.

Debnath

Jenkins

Patidar

, et al. Understanding residential occupant cooling behaviour through electricity consumption in warm-humid climate. Buildings 2020; 10.

Satola

Houlihan-Wiberg

Gustavsen

. Global sensitivity analysis and optimisation of design parameters for low GHG emission lifecycle of multifamily buildings in India. Energy Build 2022; 277: 112596.

10.

Kumar

Thakur

. Energy performance of typical large residential apartments in Kolkata: implementing new energy conservation building codes of India. Clean Technol Environ Policy 2021; 23: 1251–1271.

11.

Tan

Evans

, et al. Improving building energy efficiency in India: state-level analysis of building energy efficiency policies. Energy Policy 2017; 110: 331–341.

12.

Kapoor

Deshmukh

Lal

. Strategy roadmap for net zero energy buildings in India. 2011.

13.

Chedwal

Mathur

Agarwal

, et al. Energy saving potential through energy conservation building code and advance energy efficiency measures in hotel buildings of Jaipur City, India. Energy Build 2015; 92: 282–295.

14.

Bureau Of Energy Efficiency Impact of Energy Efficiency Measures: A Report on [Internet]. Available from: www.beeindia.gov.in

15.

Gupta

Mathur

, et al. Comparison of energy-efficiency benchmarking methodologies for residential buildings. Energy Build 2023; 285: 112920.

16.

Bhatnagar

Mathur

Garg

. Development of reference building models for India. J Build Eng 2019; 21: 267–277.

17.

Sustainable and Smart Space Cooling Coalition. Thermal comfort for all - sustainable and smart space cooling. New Delhi: Alliance for an Energy Efficient Economy, 2017.

18.

Bekun

Gyamfi

Onifade

, et al. Beyond the environmental Kuznets Curve in E7 economies: accounting for the combined impacts of institutional quality and renewables. J Cleaner Prod 2021; 314: 127924.

19.

Saini

Meena

Raj

, et al. Net zero energy consumption building in India: an overview and initiative toward sustainable future. Int J Green Energy 2022; 19: 544–561.

20.

Raj

Meena

Agarwal

, et al. A review on numerical approach to achieve building energy efficiency for energy, economy and environment (3e) benefit. Energies (Basel) 2021; 14.

21.

AlFaris

Juaidi

Manzano-Agugliaro

. Intelligent homes’ technologies to optimize the energy performance for the net zero energy home. Energy Build 2017; 153: 262–274.

22.

Ullah

Prodanovic

Pignatta

, et al. Technological advancements towards the net-zero energy communities: a review on 23 case studies around the globe. Sol Energy 2021; 224: 1107–1126.

23.

Feng

Zhang

, et al. A review of net zero energy buildings in hot and humid climates: Experience learned from 34 case study buildings. Renew Sustain Energy Rev 2019; 114.

24.

Bano

Sehgal

. Finding the gaps and methodology of passive features of building envelope optimization and its requirement for office buildings in India. Thermal Sci Eng Progress 2019; 9: 66–93.

25.

Lin

Zhong

Yang

, et al. Towards zero-energy buildings in China: a systematic literature review. J Cleaner Prod 2020; 276.

26.

Sudhakar

Winderl

Priya

. Net-zero building designs in hot and humid climates: a state-of-art. Case Studies Thermal Eng 2019; 13: 100400.

27.

Raj

Meena

Agarwal

, et al. A review on numerical approach to achieve building energy efficiency for energy, economy and environment (3E) benefit. Energies 2021; 14: 4487.

28.

Evins

. A review of computational optimisation methods applied to sustainable building design. Renewable Sustainable Energy Rev 2013; 22: 230–245.

29.

Al-Saadi

Al-Jabri

. Optimization of envelope design for housing in hot climates using a genetic algorithm (GA) computational approach. J Build Eng 2020; 32: 101712.

30.

Harkouss

Fardoun

Biwole

. Passive design optimization of low energy buildings in different climates. Energy 2018; 165: 591–613.

31.

Chen

Yang

. Integrated energy performance optimization of a passively designed high-rise residential building in different climatic zones of China. Appl Energy 2018; 215: 145–158.

32.

Kumar

Singh

Loftness

, et al. Thermal comfort assessment and characteristics of occupant's behaviour in naturally ventilated buildings in composite climate of India. Energy Sustain Dev 2016; 33: 108–121.

33.

Barman

Chowdhury

Mathur

, et al. Assessment of the efficiency of window integrated CdTe based semi-transparent photovoltaic module. Sustain Cities Soc 2018; 37: 250–262.

34.

Liu

Zhou

Tian

, et al. A comprehensive analysis on definitions, development, and policies of nearly zero energy buildings in China. Renew Sustain Energy Rev 2019; 114: 109314.

35.

Singh

Verma

. Zero-energy buildings—a review. SAMRIDDHI: J Phys Sci Eng Technol 2014; 5: 143–150.

36.

Zhang

Zhou

Hinge

, et al. Governance strategies to achieve zero-energy buildings in China. Build Res Inform 2016; 44: 604–618.

37.

Marszal

Heiselberg

Bourrelle

, et al. Zero energy building – a review of definitions and calculation methodologies. Energy Build 2011; 43: 971–979.

38.

Esbensen

Korsgaard

. Dimensioning of the solar heating system in the zero energy house in Denmark. Sol Energy 1977; 19: 195–199.

39.

Torcellini

Pless

Deru

, et al. Zero energy buildings: a critical look at the definition; preprint [Internet]. 2006. Available from: http://www.osti.gov/bridge.

40.

De Rubeis

Nardi

Ambrosini

, et al. Is a self-sufficient building energy efficient? Lesson learned from a case study in Mediterranean climate. Appl Energy 2018; 218: 131–145.

41.

Harkouss

Fardoun

Biwole

. Optimization approaches and climates investigations in NZEB—a review. Build Simul 2018; 11: 923–952.

42.

Belussi

Barozzi

Bellazzi

, et al. A review of performance of zero energy buildings and energy efficiency solutions. J Build Eng 2019; 25: 100772.

43.

Wei

Skye

. Residential net-zero energy buildings: review and perspective. Renew Sustain Energy Rev 2021; 142.

44.

D'Agostino

Mazzarella

. What is a nearly zero energy building? Overview, implementation and comparison of definitions. J Build Eng 2019; 21: 200–212.

45.

Chaturvedi

Kumar

Lamba

. Multi-objective optimization-based methodological framework for net zero energy building design in India. In: Artificial intelligence, blockchain, computing and security volume 1. CRC Press, 2024, pp. 187–194.

46.

Marszal

Heiselberg

Bourrelle

, et al. Zero energy building – a review of definitions and calculation methodologies. Energy Build 2011; 43: 971–979.

47.

Carlisle

Otto

Geet

, et al. Definition of a “Zero Net Energy” Community [Internet]. 2009. Available from: http://www.osti.gov/bridge

48.

Moghaddasi

Culp

Vanegas

, et al. Net zero energy buildings: Variations, clarifications, and requirements in response to the Paris agreement. Energies 2021; 14.

49.

Sartori

Napolitano

Voss

. Net zero energy buildings: a consistent definition framework. Energy Build 2012; 48: 220–232.

50.

Williams

Mitchell

Raicic

, et al. Less is more: a review of low energy standards and the urgent need for an international universal zero energy standard. J Build Eng 2016; 6: 65–74.

51.

Gopal

. The predicament of culture, twentieth century ethnography, literature and art by James Clifford. Cambridge J Anthropol 1990; 14: 92–97.

52.

Ryan

. Energy productivity and energy demand: experimental evidence from Indian manufacturing plants. Nat Bureau Econ Res 2018.

53.

Lan

Wood

Yuen

. A holistic design approach for residential net-zero energy buildings: a case study in Singapore. Sustain Cities Soc 2019; 50.

54.

Phillips

Troup

Fannon

, et al. Triple bottom line sustainability assessment of window-to-wall ratio in US office buildings. Build Environ 2020; 182.

55.

Costa-Carrapiço

Raslan

González

. A systematic review of genetic algorithm-based multi-objective optimisation for building retrofitting strategies towards energy efficiency. Energy Build 2020; 210.

56.

Chandel

Sharma

Marwaha

. Review of energy efficiency initiatives and regulations for residential buildings in India. Renew Sustain Energy Rev 2016; 54: 1443–1458.

57.

Energy Conservation Building Code FAQs ECBC 2017: Bureau of Energy Efficiency (beeindia.gov.in) (efficiency, 2001–22)

58.

Bureau of energy efficiency, 2001–22. Impact of energy efficiency measures, s.l.: BEE, Ministry of power, Dew Delhi.

59.

BHC ND. UK–India Science ministers announce joint research projects to address shared challenges. 2017. Available from: https://www.gov.uk/government/news/uk-india.

60.

RESIDE. Department of science and technology, ministry of science and technology, government of India. Available from: reside (reside-energy.org).

61.

Pilot Version Abridged Reference Guide [Internet]. 2018. Available from: www.igbc.in

62.

Ministry pf power goi. ECO NIWAS SAMHITA. 2018: ECBC Residential | Bureau of Energy Efficiency (beeindia.gov.in).

63.

Sood

Chang

, et al. Factors impacting integrated design process of net zero energy buildings: an integrated framework. Int J Construct Manag 2022; 22: 1700–1712.

64.

Iyer

Kumar

Mathew

, et al. Establishing a commercial buildings energy data framework for India: A comprehensive look at data collection approaches, use cases and institutions.

65.

Khosla

. Volvo - Eicher Headquarter, Gurgaon 2017. Available from: Volvo - Eicher Headquarter, Gurgaon by Romi Khosla, Architect in Delhi, Delhi, India (zingyhomes.com).

66.

Volvo-Eicher Corporate Headquarter in Gurgaon, India by Romi Khosla Design Studios [Internet].

67.

Chaturvedi

Sharma

. Energy efficiency analysis for a high rise office building in India hot and dry climate by Equest. Int J Sci Res Dev 2020; 8.

68.

Bano

Sehgal

. Evaluation of energy-efficient design strategies: comparison of the thermal performance of energy-efficient office buildings in composite climate, India. Sol Energy 2018; 176: 506–519.

69.

IGBC’s Initiatives for Advancing Net Zero Energy Buildings: Indian Green building council (igbc.in).

70.

GRIHA, 2018. Case study of SBD1, Infosys Limited, Hyderabad. (Retrieved February 12, 2018, from Green Rating for Integrated Habitat Assessment, India: http://grihaindia.org/images/casestudies/pdf/Infosys-hyderabad.pdf).

71.

Infosys Hyderabad Building Awarded Highest LEED Rating [Internet]. Available from: www.sec.gov.

72.

Srinivas

. Green Building Congress 2005. IGBC Green Habitate, A newsletter on Green Building, October. 2005. (Retrieved November 22, 2017, from https://igbc.in/igbc/html_pdfs/newsletter/Green%20Habitat%20October%202005.pdf).

73.

Regnier

Sun

Hong

, et al. Quantifying the benefits of a building retrofit using an integrated system approach: a case study. Energy Build 2018; 159: 332–345.

74.

Indio way: https://newbuildings.org/resource/verified-zne-building-case-study-435-indio-way/.

75.

South b. LEED platinum energy performance case study 2010 [Available from: Blackstone South Energy Audit (harvard.edu).

76.

Pasunuru

Hakim

Sakhalkar

, et al. (ed.). Towards net zero energy schools - A case study approach. In: Proceedings of the Winter Simulation Conference 2014, 01 December 2014. IEEE.

77.

Sang

Pan

Kumaraswamy

. Informing energy-efficient building envelope design decisions for Hong Kong. Energy Procedia 2014; 62: 123–131.

78.

Rick diamond w, memberashrae. Model FOR China’s Future Shenzhen Institute of Building Research Headquarters. 2014.

79.

Feng RDaW. Sustainability by Design How One Building in China Could Change the World.

80.

US Green Building Council. Leadership in energy and environment design: USGBC homepage | U.S. Green Building Council

81.

Huang

Zhao

, et al. Post-evaluation of energy consumption of the green retrofit building. Energy Procedia 2019; 158: 3608–3613.

82.

Zhou

Feng

Zhang

, et al. The operational performance of “net zero energy building”: a study in China. Appl Energy 2016; 177: 716–728.

83.

Somani

Bhatnagar

. Stringency analysis of building envelope energy conservation measures in 5 climatic zones of India. Build Simul 2015: 751–758.

84.

Pisello

. State of the art on the development of cool coatings for buildings and cities. Sol Energy 2017; 144: 660–680.

85.

Bardhan

Debnath

. Towards daylight inclusive bye-law: daylight as an energy saving route for affordable housing in India. Energy Sustain Dev 2016; 34: 1–9.

86.

Chiesa

Acquaviva

Grosso

, et al. Parametric optimization of window-to-wall ratio for passive buildings adopting a scripting methodology to dynamic-energy simulation. Sustainability 2019; 11: 3078.

87.

Luo

. Research on adaptive control lighting system in buildings with near-zero energy consumption. Power Syst Clean Energy 2017; 33: 1–5.

88.

Attia

Hamdy

O’Brien

, et al. Assessing gaps and needs for integrating building performance optimization tools in net zero energy buildings design. Energy Build 2013; 60: 110–124.

89.

Chaturvedi

Kumar

Lamba

. Multi-objective optimization for visual, thermal, and cooling energy performance of building envelope design in the composite climate of Jaipur (India). Energy Environ 2024: 0958305X241228513.

90.

Bano

Sehgal

. A comparative study: energy performance analysis of conventional office buildings at Lucknow. J Design Built Environ 2020; 20: 24–34.

91.

Kumar

Thakur

. Energy performance of typical large residential apartments in Kolkata: implementing new energy conservation building codes of India. Clean Technol Environ Policy 2021; 23: 1251–1271.

92.

Bano

Sehgal

Tahseen

. Early-stage design guidelines for net-zero-energy office buildings in tropical climate. In: 2020 International Conference on Contemporary Computing and Applications (IC3A), 5 February 2020. IEEE, pp. 143–149.

93.

Chedwal

Mathur

Agarwal

, et al. Energy saving potential through energy conservation building code and advance energy efficiency measures in hotel buildings of Jaipur City, India. Energy Build 2015; 92: 282–295.

94.

Tulsyan

Dhaka

Mathur

, et al. Potential of energy savings through implementation of energy conservation building code in Jaipur city, India. Energy Build 2013; 58: 123–130.

95.

Bhatnagar

Mathur

Garg

. Development of reference building models for India. J Build Eng 2019; 21: 267–277.

96.

Cabeza

Chàfer

. Technological options and strategies towards zero energy buildings contributing to climate change mitigation: a systematic review. Energy Build 2020; 219: 110009.

97.

Karunathilake

Hewage

Sadiq

. Opportunities and challenges in energy demand reduction for Canadian residential sector: a review. Renew Sustain Energy Rev 2018; 82: 2005–2016.

98.

U. bureau of energy efficiency, “NZEB.IN,” [Online]. Available: https://nzeb.in/.

99.

Sudhakar

Winderl

Shanmuga Priya

. Net-zero building designs in hot and humid climates: a state-of-art. Case Stud Thermal Eng 2019.

100.

Soni

Bhagat Singh

. First onsite net zero energy green building of India. Int J Environ Sci Technol 2020; 17: 2197–2204.

101.

Sen

Bhattacharya

Chattopadhyay

. Are low-income mass housing envelops energy efficient and comfortable? A multi-objective evaluation in warm-humid climate. Energy Build 2021; 245: 111055.

102.

Bhamare

Rathod

Banerjee

. Passive cooling techniques for building and their applicability in different climatic zones—the state of art. Energy Build 2019; 198: 467–490.

103.

Rezaei

Shannigrahi

Ramakrishna

. A review of conventional, advanced, and smart glazing technologies and materials for improving indoor environment. Sol Energy Mater Sol Cells 2017; 159: 26–51.

104.

Zhang

. Multi-objective optimization of energy, visual, and thermal performance for building envelopes in China's hot summer and cold winter climate zone. J Build Eng 2022; 59: 105034.

105.

Srivastava

Khan

Bhandari

, et al. Calibrated simulation analysis for integration of evaporative cooling and radiant cooling system for different Indian climatic zones. J Build Eng 2018; 19: 561–572.

106.

Vakiloroaya

Samali

Fakhar

, et al. A review of different strategies for HVAC energy saving. Energy Convers Manage 2014; 77: 738–754.