Challenges That Impact the Development of a Multi-Generational Low-Carbon Passive House in a Small City

: The impact of the building and construction sector on climate change is becoming more important and recognized. Multiple initiatives around the globe have been utilized to design and develop residential structures, aiming to reduce energy consumption and carbon emissions; yet, there are several barriers to effective construction processes. This research outlines the gaps and barriers encountered by key stakeholders that were engaged during the preconstruction phase of a three-story multi-generational low-impact Passive House in Fayetteville, Arkansas. Through direct observation and open-ended interviews, the primary data are collected, and secondary data from a comprehensive literature review are detailed to capture the challenges faced during different phases of the implementation of sustainable residential dwellings. This study highlights the limited knowledge and experience in sustainable building design as a common barrier among participants along with the insufficiency of the regulatory framework governing adopted building codes in Arkansas, in facilitating sustainable building design implementation. These challenges, among others, are then thoroughly examined, and recommendations to address them are described.


Introduction
The building and construction sector is a major contributor to global carbon emissions through construction and energy consumption, and addressing climate issues and carbon reduction has become a vital goal worldwide [1].Passive Houses, Net-Zero-Energy (NZE) Buildings, and Zero-Carbon Buildings are examples of building types developed to achieve this goal and that aim to minimize embodied and operational energy use and carbon emissions throughout the building's life cycle.Passive Houses are one of these typologies, which offer a promising solution for achieving exceptional energy efficiency and sustainability while ensuring occupant comfort [2].
The construction process can be divided into three main stages: preconstruction, construction, and postconstruction phases.The preconstruction phase focuses on the planning and design, where the project's size, location, architectural, structural, mechanical, and electrical designs are prepared and permitting is ensured to launch the construction works.The construction phase includes bringing down the design drawings' specification and procurement on site and ensuring all specifications are met.The project completion stage is where the project is finalized and handed over to the owner [3].Each of these phases presents its own challenges that emerge during the construction process and can affect project completion [4].
The design and construction of low-carbon and energy-efficient houses can have significant challenges during various phases of the project, especially in regions where the concept is still relatively new and unfamiliar [5], and where the design and construction involves a unique set of considerations, such as finding qualified and motivated engineers, complying with regulatory frameworks, managing the material and supply chain, and dealing with the special construction requirements for these types of buildings [2].The purpose of this research paper is to shed light on these barriers, and to provide insights into the experience of the stakeholders engaged in the design and permitting of the Everly House, also known as the Caja House.The house was designed as a triplex multi-generational low-carbon Passive House in Fayetteville, Arkansas, in a city in a humid subtropical climate of the southern United States.This study is unique in its in-depth analysis of the preconstruction phase from the initial stages that can affect a low-carbon Passive House in the suburbs of a growing small city in the United States.This study provides an overview of the barriers faced by professionals engaged in this study that can inform future sustainable building projects, in areas where similar practices are not common.By examining these barriers and their potential solutions, this study seeks to contribute to the development of strategies and recommendations that can facilitate the design and permitting process for future Passive House projects in a similar context.

Literature Review
The Passivhaus standard is generally defined as a low-energy building that achieves indoor thermal comfort [6].This concept was developed in Europe by the end of 1988 by Wolfgang Feist from Germany and Bo Adamson from Sweden [7].The design of the first Passivhaus was established in 1991, resulting in a super-insulated building [8].The concept was formulated according to Passivhaus standards that are reviewed through the Passivhaus Institute (PHI), an internationally recognized research institution that was established in 1996 to provide the guidance, design, and certification of houses meeting the performance standards [2].In North America, the term Passive House is often used to refer to energy efficiency buildings, where the Passive House Institute (US PHIUS) provides certification for buildings that meet the requirements of PHIUS Standards for building energy modeling.Originally part of PHI, PHIUS was established to tailor the standards to North American climate.A break in the agreement resulted in the two institutions providing for separate Passive House certification in North America [9] with differences in criteria for heating and cooling, air tightness, energy, and the energy modeling tools [10].For the modeling tool, PHIUS uses Wärme Und Feuchte Instationär (WUFI) while PHI uses the Passive House Planning Package (PHPP) as an informing tool for project certification [11].The decision to choose one of these options for the Passive House certification solely depends on the architect, engineer, and owner [2,12] The US Department of Energy (DOE) defines an NZE building as an energy-efficient edifice that generates as much or more energy than it consumes over a year through onsite renewable energy sources [13], resulting in a net-zero balance of energy use and emissions [14].The design of an NZE building demands the implementation of specific energy performance strategies, design concepts, and technologies [15].The measurement and classification of NZE performance varies, contributing to common challenges and barriers encountered during the implementation of NZE building projects [16].These challenges result from multidimensional factors that are related to technical knowledge and expertise of professionals, efficient project management, project cost implications, policies and regulatory requirements, and dealing with market barriers [17].
Research conducted in both developed and developing countries has identified many challenges in implementing sustainable building practices that are related to the cost, timing, regulations, knowledge gap, and lack of incentives and support [18].For instance, a recent study conducted in New Zealand about the slowdown in construction of NZE buildings concluded that legislations and policies are the main challenges in incentivizing and encouraging the adoption of these types of buildings while the impact of financial and technical challenges is limited [19].The challenges, however, can be different among countries, cities, and states.For example, a study conducted in Nigeria found that the main challenges to adopting sustainable construction practices are related to the lack of experience among professionals, lack of clear strategies to promote sustainable constructions, and lack of demand among different stakeholders to adopt sustainable construction [20].As for other examples, a study conducted in southern Europe has highlighted technical and social challenges in implementing Nearly Zero-Energy Buildings (NZEB) [21], and a study in Portugal found that the main obstacles to implementing the Passive House concept were related to a lack of knowledge among building industry technicians and key actors [22].
This literature review highlights eight categories of barriers and challenges that affect the project implementation phases.The first phase is comprised of the issues arising during the project inception period and includes cultural and social constraints and project management [17,20].The second phase, or preconstruction phase, covers design and permitting, and includes the technical challenges, knowledge gap, legislative and regulatory barriers, and financial constraints [20][21][22][23].During the last phase or the construction work, delays are caused by barriers arising from knowledge gaps and project management [23,24].
Results of this literature review highlighting the common barriers and challenges (CBCs) to sustainable buildings including Passive Houses and NZE buildings are summarized in Table 1 below.

Phase Challenges References
Knowledge Gaps All Phases Lack of awareness, understanding, experience, information, findings, and studies [17] Development and Evaluation All Phases Scarcity in methods, tools, applications, technologies, and adopting models for design, construction, and assessment [17] Technical Challenges

Preconstruction and Construction
Lack of construction skills and quality assurance mechanisms [21] Preconstruction and Construction Inappropriate use of design methodologies coupled with limited input from performance evaluation [20][21][22]

Preconstruction and Construction
Barriers related to professionals' knowledge and practice in dealing with new technologies and standards [20,21] Legislative and Regulatory Barriers Preconstruction Absence of mandatory standards for innovative construction methods, materials, and design [20,23,24] Preconstruction and Construction Legal and construction barriers leading building owners to invest in renewable energy sources instead of energy efficiency [21,22] Preconstruction Variation between climate zones requiring different approaches to achieve NZE [21] Construction Lack of experience and knowledge among developers, contractors, and builders [23,24] Timing All Phases Cooperation and networking [23] All Phases Knowledge, tools, and methods [23] All Phases Regulations and client understanding [23] Cultural and Social Constraints Preconstruction Preferences of suppliers/institutional buyers [23] Preconstruction Limited acceptance of the concept itself in the market [22] Inception Phase Focus on short-term construction industry benefits rather than incorporating sustainability principles in the design phase [20] Inception Phase Lack of client demand [20] Managerial Constraints All Phases Lack of commitment of senior management; lack of sustainable project management [23] Table 1.Cont.

Phase Challenges References
Financial Constraints Preconstruction Financial limitations, insufficiently developed proactive strategies, and constraints related to both financial resources and planning efforts [23] Preconstruction Lack of public policies and incentives for PH-concept-based construction [22]

Methodology
Everly Passive House is the case study under investigation for the specific challenges and barriers faced during the preconstruction phase.The Everly Caja residence is a threestory residential house with a total area of around 300 m 2 (3300 ft 2 ).The house is designed to operate as a Passive House with low operating energy demand.The house design also considers the material enclosure used to lower carbon emission as well as providing low energy demand.

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Suite A-An elderly accessible single bedroom house located on the 1st floor; designed for couples; includes one bedroom, and one large bathroom with curb-less shower and wheelchair modification ready.

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Suite B-Designed as a small family residential floor, and includes three bedrooms, two bathrooms, an office space, an open kitchen, and a living room.

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Suite C-Designed as a studio and can be combined with Suite B.
This study employs a triangulated approach that combines the use of data from multiple sources [25], among them a literature review, direct observations, and openended interviews.The collection of data from multiple sources enhances the validity and reliability of the findings [26], and allows the development of a complete understanding of the problem [25].The preconstruction phase is critical as it sets the foundation for the project, as it involves finalizing the design, securing permits, and planning for variations.It is during that phase that many challenges are faced, which could potentially lead to not completing the project.These barriers are often related to regulatory and code compliance, design modifications, material selection, and other factors specific to sustainable building practices.
The use of a literature review in this study allows capturing the different barriers faced by sustainable buildings, providing a comprehensive thematic review of these barriers and confirming the findings of this study [27].On the other hand, the direct observation offers unique opportunities to the researchers to capture, through direct engagement in a realworld setting, interactions and incidents that other methods can miss or misinterpret and help fill the gap between theory and practice [28].The open-ended interview through purposeful sampling offers selecting participants that play pivotal roles in the preconstruction phase of the Everly Passive House.The richness of the information provides a comprehensive understanding of the challenges.This approach ensures that each participant could offer substantial insights into the encountered challenges and barriers [29].
(a) Literature Review A systematic approach is followed in the literature search to ensure a rigorous and comprehensive identification of relevant articles.The review process is focused on the discovery of scientific documents that specifically identify the challenges faced during the preconstruction and construction of sustainable buildings.A combination of keyword searches and database filters are used to identify relevant articles.The search criteria include terms such as "barriers to sustainable building design", "challenges in sustainable building permitting", "obstacles in sustainable construction", and related variations.These documents are then screened based on relevance to the research topic and included for a detailed analysis.Only articles that provide insights on challenges faced during the implementation of sustainable buildings are included for further analysis.Next, the identified challenges are categorized and segregated according to the stage of construction in which they mostly occur.This approach enabled a structured analysis of the challenges, providing a deeper understanding of the barriers at each stage of the construction process.

(b) Interviews
Interviews were conducted and the key barriers were identified and categorized.The barriers are then classified into themes that share common elements (e.g., communication channels, technical skills, design implementation).The elements represent the factors contributing to each identified barrier, which are identified through a process of a thematic analysis of the interview transcripts.The categorization is based on the nature of these barriers (e.g., technical, regulatory, financial) and its impact on the project (e.g., delay, cost increase).Barriers are grouped into themes that share common elements.Themes are analyzed based on the frequency of response, which is quantified by counting the number of times each barrier is mentioned across all interviews [30].Themes are weighted based on their observed impact on project time and goals, which is assessed by considering the severity of the delay or cost increase caused by each barrier, as reported by the interviewees.Selected comments and quotations from the interviews are included in the analysis to provide a richer understanding of the identified barriers.These direct quotes serve as supporting evidence and offer firsthand perspectives and insights from the respondents [31].The comments and quotations are selected to represent a range of perspectives and to highlight the challenges faced during the preconstruction phase.
This study employed a purposeful sampling strategy where interviews are directed at city officials, engineers, and architects engaged in the Everly House preconstruction phase, as well as the owner.A total of nine professionals responsible for developing geotechnical, structural, architectural, and mechanical design were identified.The interview questionnaire was shared with these professionals, along with two city representatives and the project owner.We received responses from the structural and mechanical engineers (E1 and E2), the two architects from the architectural firm (A1 and A2), and the two official representatives from the city of Fayetteville (R1 and R2), in addition to the owner who also acts as the main contractor of the house.These seven interviews represent the entirety of this group, thus providing a complete picture of challenges faced during this phase.Follow-up interviews and questions are also shared with some participants for clarification and requesting additional information for this study.The interview questions are conceived to capture the interviewees' viewpoints and experience in the design and permitting of this house as well as their experience as part of professional bodies and regulatory agencies in the challenges and barriers to implementing sustainable buildings in fast-growing cities.The questions ranged from exploring the dynamics of collaboration and communication among stakeholders to understanding the detailed design challenges and material selection, in addition to the potential challenges that could impact the success of similar projects in the future.

(c) Direct observation
In addition, the research is based on direct observation to gain insights into the process of developing similar projects as well as to understand common challenges faced during the preconstruction of Everly House.The observation period spanned from August 2022 to May 2023.During this period, the authors closely observed the design and permitting process through direct engagement with the project owner.This engagement consisted of weekly meetings, recorded in written meeting notes, which included progress updates, decisions made, and discussions.The discussions were centered around reasons behind any changes made to the project plan, issues related to design iterations, and other topics.The outcome of the direct observation assisted in scoring the barriers.
A scoring methodology was conducted using a binary scoring system to simplify the analysis in direct observation into 'observed' and 'not observed' [32], to understand the presence of a specific barrier in each stage of the preconstruction of the project.If the barrier was observed in the planning, conceptual design, or final design and permitting, it was given a score of 1; if not, it was scored as 0. The barrier is then weighed based on the sum of the scores across the three stages where the result ranged from 0 to 3.This method allowed the reflection of the cumulative impact of these barriers on the project, and provided an informative analysis of the relationship between the exploratory variables (observed and not observed barriers) and the dependent variable (the weight) [33].
Additionally, a collaboration folder between the owner and the architectural firm was shared by the project owner with the authors.The folder includes project architectural, mechanical, and structural design plans and material data sheets.This folder serves as an essential source for project documents during the follow-up period and represents a primary source of data for the analysis.
Relevant documents, such as mechanical design reports, structural design calculation notes, WUFI Energy simulation reports, permit draft documents, and relevant regulations such as Fayetteville, Arkansas Energy Code of Ordinances, 2009 International Energy Conservation Code (IECC), 2021 International Building Code (IBC) and 2021 International Residential Code (IRC), and Arkansas Fire Prevention Code Volume I, adopted by the state of Arkansas, are reviewed to supplement the observation data.

Results
The barriers can be summarized into six main categories, which were highlighted by the interviewees and observed during the follow-up period.The six categories include 20 barriers faced at different stages, where each barrier is represented as a theme; themes are related to elements representing factors causing these challenges depending on the nature of the barrier, and these elements are used to develop recommendations to overcome these barriers.Table 2 is a summary of the categories, themes, and elements along with weighing these barriers based on their impact on the project timeline ranking from low-to high-impact barriers, and the frequency of times they are mentioned in the interviews.The preconstruction phase of the Everly project has three main stages: planning, conceptual design development, detailed design and permitting [31].The barriers are not isolated to one stage but do rather overlap, interact, and result from the difficulties or gaps encountered by the various stakeholders involved in the project.To provide an understand-ing of the relationship between project participants, project stages, and identified barriers, a diagram has been developed (Figure 1).This diagram briefly explains the relationship between project participants, the three main stages during the preconstruction phase, and the main barriers encountered in these stages.

Management and Time Barriers
"A lot of changes came but not all at one time so there were many iterations which made us constantly need to reevaluate how we are meeting the standards", said A1, a sentiment echoed by E1, "One should get a schematic plan in front of the permitting people as early as possible and to get everyone on board as early as possible." For example, the design of the Everly House changed substantially in response to the discovery of zoning requirements for a property in a flood plain that required raising the residential quarters a minimum of 0.6 m from the surface (Figure 2).Moreover, WUFI modeling of the original design revealed the need for additional shading and insulation to meet Passive House energy goals (Figure 2).

Management and Time Barriers
"A lot of changes came but not all at one time so there were many iterations which made us constantly need to reevaluate how we are meeting the standards", said A1, a sentiment echoed by E1, "One should get a schematic plan in front of the permitting people as early as possible and to get everyone on board as early as possible." For example, the design of the Everly House changed substantially in response to the discovery of zoning requirements for a property in a flood plain that required raising the residential quarters a minimum of 0.6 m from the surface (Figure 2).Moreover, WUFI modeling of the original design revealed the need for additional shading and insulation to meet Passive House energy goals (Figure 2).Challenges associated with management and time are common among sustainable building projects across the construction project phases (Table 1, e.g., Timing and Managerial Constraints).The Everly House faced similar challenges during the preconstruction phase, and one key barrier that had the highest impact on this project was the lack of an integrated design approach among architectural, structural, geotechnical, mechanical, and sustainable building designs that resulted in multiple design revisions.The inadequacy of coordination was mentioned several times by the design professionals during their interviews, indicating a recurrent theme.A1, for example, noted the multifaceted nature of design alterations stemming from diverse factors such as project location, structural modifications, and regulatory requisites.
To overcome this barrier, it is important to establish clear lines of communication and coordination between architects, structural engineers, geotechnical experts, mechanical engineers, and sustainable building designers from the very early stages of planning.Regular project meetings coupled with the comprehensive documentation of decisions foster Challenges associated with management and time are common among sustainable building projects across the construction project phases (Table 1, e.g., Timing and Managerial Constraints).The Everly House faced similar challenges during the preconstruction phase, and one key barrier that had the highest impact on this project was the lack of an integrated design approach among architectural, structural, geotechnical, mechanical, and sustainable building designs that resulted in multiple design revisions.The inadequacy of coordination was mentioned several times by the design professionals during their interviews, indicating a recurrent theme.A1, for example, noted the multifaceted nature of design alterations stemming from diverse factors such as project location, structural modifications, and regulatory requisites.
To overcome this barrier, it is important to establish clear lines of communication and coordination between architects, structural engineers, geotechnical experts, mechanical engineers, and sustainable building designers from the very early stages of planning.Regular project meetings coupled with the comprehensive documentation of decisions foster alignment amongst all stakeholders with the overarching project vision and objectives.
Designs 2024, 8, 52 10 of 17 Ultimately, this approach can reduce the number of design revisions, and reduce the project timeline.

Sustainable Design Barriers
"We seemed to be looking at the design process from two different directions", said the owner.In parallel, E2 pointed out that "The impact of design decisions and assumptions is greater than that of any specific tool in Mechanical Engineering and Plumbing (MEP) systems.These systems have historically been oversized due to outdated rules of thumb and dynamic design conditions." For example, there is a difference between conventional design and Passive House design assumptions for the thermostat settings.The conventional thermostat setting, initially used in the design of the Everly Passive House, is set between 21 and 24 degrees Celsius (70 and 75 degrees Fahrenheit); however, the Passive House paradigm mandates a much wider range of 20 to 25 degrees Celsius (68 to 77 degrees Fahrenheit).The indoor design temperature assumption affects the heating, ventilation, and air conditioning (HVAC) system, leading to oversizing due to disparities in thermal requirements, where heating transmission load increases and cooling transmission load decreases when increasing indoor design temperature [34] for the final design.The heating load estimated through WUFI was approximately 17,141 Btu/h while the estimated value through Hourly Analysis Program (HAP) was 14,321 Btu/h, and the cooling load estimated through WUFI was approximately 7737 Btu/h, while the estimated sensible and latent cooling loads calculated in HAP were 21,991 Btu/h and 1640 Btu/h, respectively.
Designers and engineers, by and large, prefer conventional design and material over sustainable design approaches (Table 1, Development and Evaluation and Technical Challenges).The common barrier illustrated in the above example is the lack of alignment between design decisions and the project vision and objectives, which results in suboptimal or incompatible design solutions.
Another barrier stems from the lack of integration between architectural design, HVAC systems, and structural design, hindering the quest for optimal energy efficiency.For example, the designer of a Passive House assumes the infiltration in the HVAC design in all zones to be negligible due to tight construction; however, real-world observations reveal a significant disparity between this assumption and the physical setting, where infiltration occurs through cracks in building envelopes and through natural ventilation caused by opening doors and windows, which allows outdoor air to enter [35].These examples emphasize how such differences in design assumptions can lead to significant effects on system efficiency and energy consumption.

Regulatory, Permitting, and Legislation Barriers
"Additionally the house design doesn't meet the typical design requirements stated in the fire code for single house, and it was considered a Triplex that requires additional modification to meet standards," said R1, and "The codes are not written to address Passive [House] design explicitly," according to R2, who also noted that "The State of Arkansas does not give us much ability to regulate building materials for single-family homes in our zoning codes." Even though adopted regulations and policies related to sustainable building design differ among countries, states, and cities [20], regulatory barriers remain common among different projects.The analysis identified several barriers related to regulatory frameworks, permitting processes, and legislative aspects.The inadequate integration of energy efficiency, carbon reduction, and sustainable building design standards within building codes and urban planning regulations emerged as a critical barrier.The house was designed as a single-family house, there was a modification from two to three stories due to requirements for a property in a flood plain, and the house was reclassified as a triplex, which required interior modification and the installation of utilities on the premises.As highlighted by R1, this barrier of code non-compliance causes design modifications and delays in permit-ting.Even though these codes are not directly related to energy or carbon reduction, they, however, affect the shape and physical layout of the house originally decided on based on sustainable design principles such as the building orientation, number of floors, and internal loads, in addition to carbon reduction and ecological footprint principles that are related to the type of foundation, structural design, and type of material used in addition to the building layout.
The absence of specific and clear guidance on sustainable building design requirements in the adopted building codes can lead to uncertainty among project designers to integrate sustainable building practices into their projects and can also result in a lack of interest in designing for energy saving and carbon reduction.This gap highlights the need to advocate for adopting updated building energy codes and provide consistency and standardization through including clear requirements and guidance to make informed decisions and align the design with code requirements as well as sustainable building practices [18].

Knowledge Gap and Experience Barriers
"The lack of literature and experts who knew about these systems made our task more complex," said E2, and A2 pointed out, "Most of the challenges faced during this [preconstruction] phase is primarily rooted in a general lack of experience in this region with Passive House design and the technologies being used in this house." A similar observation was made by the structural engineer (E1) regarding the challenges associated with nontraditional design approaches to reduce the carbon footprint such as the limited use of concrete structures in the project, as well as vertical capacities that include the use of fiberglass composite posts instead of using traditional materials like steel and concrete, and lateral capacities that use bracing systems to enhance lateral stability or hybrid systems such as glulam beams and timber for lateral bracing [36,37].This lack of familiarity with advanced design strategies and technologies affects the delivery of design drawings in addition to several trade-offs that increase the carbon footprint and oversize the structural beams.
Challenges associated with the knowledge and experience of professionals engaged in the design and implementation of sustainable building projects are another common barrier among similar projects (Table 1, Knowledge Gap).One barrier identified in this study is associated with the gaps in knowledge and experience among design professionals.The lack of expertise and knowledge not only increases the pressure on designers to conduct extensive research but also affects their willingness to embrace innovative approaches during the design phase.
There have been other identified barriers associated with knowledge gaps and experience categories that had a moderate impact on the project and their effects were mainly on the project timeline; these barriers included the lack of awareness and understanding of available energy-efficient technologies such as the Passive House concept and energyefficient HVAC systems and difficulty in translating theoretical knowledge into practice and were also highlighted by the architects and engineers.Addressing these barriers requires training architects and engineers on sustainable design practices, energy-efficient technologies, and best practices to enhance their knowledge and expertise, and utilizing knowledge-sharing platforms and resources to enhance designers' awareness and understanding of available energy-efficient technologies and practical design solutions.

Material Selection and Supply Chain Barriers:
Although the material selection and supply chain are not highlighted, they are mostly associated with the cost, material information, and decision-making process during the design process [38].
One of the challenges that this research identified is the lack of affordable and sustainable building materials within the local market.Specifically, materials such as hemp wool, cork, and rock wool, which hold immense promise for reducing carbon footprints, are not widely accessible.For example, cork is a material that has these qualities, but it was difficult to import due to supply chain disruptions and high costs.This means that the designers and owner had to spend a lot of time searching for suitable materials to meet the criteria of a low-carbon footprint, Passive House standards, and energy efficiency.This resulted in some compromises in the original envelope material selection and trade-off in the amount of carbon reduction and energy savings without affecting the Passive House thermal enclosure requirements for assemblies, which were thermal resistance values (R-values) of the roof at 11.27-15.15m 2 •K/W (64-86 h ft 2 • F/Btu), above-grade walls, overhanging floors at 5.64-8.46m 2 •K/W (32-48 h ft 2 • F/Btu), and below-grade walls and floors at 2.82-4.23 m 2 •K/W (16-24 h ft 2 • F/Btu) [26]. Figure 3 illustrates two wall section changes that occurred between May 2022 and August 2022 due to design changes and estimation of the carbon footprint associated with envelope assembly.One of the challenges that this research identified is the lack of affordable and sustainable building materials within the local market.Specifically, materials such as hemp wool, cork, and rock wool, which hold immense promise for reducing carbon footprints, are not widely accessible.For example, cork is a material that has these qualities, but it was difficult to import due to supply chain disruptions and high costs.This means that the designers and owner had to spend a lot of time searching for suitable materials to meet the criteria of a low-carbon footprint, Passive House standards, and energy efficiency.This resulted in some compromises in the original envelope material selection and trade-off in the amount of carbon reduction and energy savings without affecting the Passive House thermal enclosure requirements for assemblies, which were thermal resistance values (Rvalues) of the roof at 11.27-15.15m 2 •K/W (64-86 h ft 2 °F/Btu), above-grade walls, overhanging floors at 5.64-8.46m 2 •K/W (32-48 h ft 2 °F/Btu), and below-grade walls and floors at 2.82-4.23 m 2 •K/W (16-24 h ft 2 °F/Btu) [26].Figure 3 illustrates two wall section changes that occurred between May 2022 and August 2022 due to design changes and estimation of the carbon footprint associated with envelope assembly.Table 3 below provides detailed information on the thermal characteristics of three different envelope assemblies that were used in the WUFI Energy model of the Everly House.The name of each assembly, its thermal resistance (R-value), its heat transfer coefficient (U-value), and its thickness (inches) are indicated for the wall, roof, and floor/slab components.These values indicated that all selected building envelopes meet the building's insulation requirements.Table 3 below provides detailed information on the thermal characteristics of three different envelope assemblies that were used in the WUFI Energy model of the Everly House.The name of each assembly, its thermal resistance (R-value), its heat transfer coefficient (U-value), and its thickness (inches) are indicated for the wall, roof, and floor/slab components.These values indicated that all selected building envelopes meet the building's insulation requirements.
The initial design envisioned the utilization of Nexcem blocks combined with mineral wool, and a slab-on-grade foundation, aligning with floodplain and Passive House design considerations.However, budget constraints, along with the carbon footprint associated with the Nexcem blocks and the floodplain permitting requirements for elevating the house on piles, affected the architectural design, leading to the selection of a 2 × 8 ′′ wall configuration, filled with cellulose insulation.While this decision was, in part, driven by the need to navigate budget constraints and logistical hurdles, it represents a tangible example of the reasons why the consequential reduction in the envelope material carbon footprint is the first to be compromised.Although the barrier is related to many gaps from the manufacturer as well as professional knowledge, professionals need to have an early engagement with the supply chain to identify the whole life cycle cost as well as the carbon footprint before the design process, and should also understand the material physical performance, the carbon footprint, and the impact of energy efficiency to meet the project goal and vision.

Tools and Software Barriers
"There are many tools being developed to make carbon-neutral design more achievable for designers, but there needs to be a lot more work done in this area to make it easier for architects to navigate the trade-offs involved in specifying materials and building processes for carbon-neutral buildings," according to A2.The architect's comments also extend to energy modeling.
For example, the drawings for the Everly House were prepared in ArchiCAD 26, by Graphisoft, Hungary, 2021 software.For the energy analysis, the ArchiCAD file had to be imported into SketchUp and from SketchUp exported into WUFI.This illustrates the lack of integration and compatibility between different software platforms [11] An attempt was initiated by the authors to develop an energy model for the Everly House using EnergyPlus 22.1 by the U.S. Department of Energy, Golden, CO, USA, and the ArchiCAD file was also faced with similar obstacles, including gaps in translating the geometry into an analytical model that can be used by EnergyPlus.This gap affects the exchange of critical project information, which, in turn, can lead to misunderstandings, discrepancies in data interpretation, and delays in decision-making and design development.
The identified barriers in this category were of moderate to low impact regarding this project; however, this analysis emphasized the importance of software integration, data sharing, and collaborative workflows as key elements to address these barriers, and the respondents emphasized the relevance of software integration, data sharing, and collaborative workflows for developing energy-efficient designs.

Conclusions
The research is based on a specific case study in Fayetteville, Arkansas, in the United States, and the findings may not be applicable to other contexts or regions.This study investigated the barriers faced during the preconstruction phase of the Everly Passive House as a case study, where sustainable building practices are not yet widely adopted and prioritized, both among local industry professionals and within state plans and regulations.Open-ended interview discussions were conducted among professionals engaged during this phase, and seven professionals including the project owner responded.A total of 20 barriers were identified through interviews and direct observation, and then were categorized in terms of the management and time, design, regulations and permitting, knowledge gap and experience, material selection, and tools and software.The findings of this study revealed a multidimensional relationship between different project stakeholders and barrier categories that affect the preconstruction phase.These findings align with the literature review conducted, in which technical challenges and legislative and regulatory barriers were more common during the preconstruction phase of this project, providing scientific evidence to support these results.
These barriers have significant impacts on each stage of the preconstruction phase; they affect the feasibility and viability of the project as well as the identification of possible risks and responsibilities.On the other hand, these barriers may compromise the adoption of carbon reduction goals, building energy-efficiency design, and compliance with certification requirements.Sustainable design and regulatory and permitting barriers were found to carry more weight, as they directly influence the foundational aspects of low carbon, energy-efficiency sustainable design, and approval processes, which are critical for the successful implementation of zero-energy and zero-carbon-emission residential buildings.It is important to address these barriers by adopting a multidisciplinary design approach that involves integrating all relevant design disciplines (architecture, HVAC, structural engineering) to work collaboratively during the concept development and final design stages and considering energy performance and environmental impact from the outset and prioritizing sustainable design principles.
In addition to that, the respondents provided valuable suggestions as solutions for problems faced, focusing on the importance of early collaboration and communication among professionals involved in the design and permitting stages; there is importance to developing knowledge and expertise of architects and engineers to implement sustainable building designs and preparing engineers and architects before graduation to incorporate sustainable approaches in their professions.These suggestions were compiled with researchers' recommendations to provide a comprehensive understanding of the challenges and necessary steps to overcome them.
This research is faced with certain limitations that need to be considered.First, some respondents were reluctant to respond to the project; however, the respondents who did participate represent key professionals who exert significant influence over the design and permitting processes of the house.Second, the identified barriers are context-specific and limited to a single case study.In other words, some identified barriers provided in Table 2 may not be relevant to other projects located in different contexts or regions where regulatory frameworks and policies prioritize and incentivize similar projects, while some barriers are identified in other studies, such as design-related challenges and knowledge gaps.Third, the research methodology relies on open-ended interview discussions to capture professionals' perspective who were directly involved in the project, and it is limited to their professional experience in this project.Fourth, the number of interviewees is limited to seven professionals, and while they provided valuable insights, the limited size may not fully represent multiple perspectives and experiences.Despite the limitations, the findings of this study are expected to be a valuable resource for project owners and professionals engaged in the initial stages of similar projects.The design modifications, retrofitting, and changes in envelope materials are all associated with professionals' knowledge, interest, and experience in Passive House design requirements and carbon reduction principles as well as the outdated and weak building energy codes and regulations that do not incorporate sustainable building design principles and do not provide comprehensive guidance on energy-efficient and low-carbon design, creating confusion and challenges for architects and engineers during the concept development phase and affecting the timeline of the project.These delays and modifications have affected the project budget and delayed the implementation of the project as well as finalizing the permit documents.Knowing the potential barriers, these stakeholders can utilize these recommendations and develop strategies to overcome them, to ensure successful project design and completion.Additionally, by understanding and addressing these barriers, policymakers, industry professionals, and researchers can work together to overcome these challenges and promote sustainable building typologies.
The research's novel contribution is its detailed examination of the barrier's professionals face during the initial stages, providing insights that are scarce in the literature, particularly in a similar context where sustainable building design is not integrated into designers' approaches and is not prioritized in municipal or state regulations.The aim of this study is to document these challenges and act as a catalyst for future research that could build on these findings and assess the applicability of the recommendations across various contexts.While this study highlights the barriers faced during the preconstruction phase of the Everly Passive House, these findings are specific to this case and may not be generalizable to other projects or regions.Future research could then extend this study to include participants from similar projects in both similar and different contexts.

Figure 1 .
Figure 1.Relationship between construction barriers, project participants, and project stages.

Figure 2 .
Figure 2. Everly House design from May 2022, building is ground-supported and 2 stories above ground level (circled in red) (top) to December 2022, building is raised on piles (circled in red) and three stories above ground level (bottom).

Figure 2 .
Figure 2. Everly House design from May 2022, building is ground-supported and 2 stories above ground level (circled in red) (top) to December 2022, building is raised on piles (circled in red) and three stories above ground level (bottom).

Table 1 .
List of Common Barriers and Challenges Identified in Literature.

Table 2 .
Identified Barriers, Associated Themes, Their Impact, and Their Frequency.

Table 3 .
Thermal Performance Characteristics of Different Envelope Assemblies.

Table 3 .
Thermal Performance Characteristics of Different Envelope Assemblies.