Keywords

Social network analysis; Social media; K-pop; Korean culture; Twitter; Gephi.

Introduction

Information and networking processing advancements in particular through the broad selection of social networking resources have demonstrated the right of contributing greatly transparent governance by not just having forums of government records data dissemination but also ways of involving stakeholders (Gao, 2018). In consideration of the increasing importance of social networking as a significant source of power, there is a deeper analysis into who leads the information sharing and above all, the trend of information sharing among such consumers becomes prevalent. The Online social network details, therefore, provide new chances and opinions to the government and control of the evaluation of large social networks and classes (Chansanam & Tuamsuk, 2020). Social networks have recently developed into essential channels for human contact and market administration, exchanging knowledge, and different facets of daily life (Desai et al., 2012).

Online networking has attracted substantial interest from information technology and communications analysts, in general social networks have an impact on variety of interesting committees. Between 1997 and 2017, an analysis of 132 academic articles on social networking mainly examined social media behavior, its marketing incentives, and its resulting organizational impact (Kapoor et al., 2018). In addition, the information sharing and exchange capacities of social media are unanimously shared. However, a particular study cluster that characterizes their efficiency in major events (Kapoor et al., 2018). This post comes under this category and discusses Tweet research by certain outlets of the social network (Oh et al., 2013; Shi et al., 2013; Miranda et al., 2016; Kapoor et al., 2018).

The key practical and theoretical contributions in this review are several studies use the theory of social interaction, network and organizational theory (Kapoor et al., 2018). First, this study uses the theory of social networks, but it adds a graphical theoretical lens to enrich the existing knowledge. In the introduction of a fresh concept in this situation (K-pop popular Twitter accounts), is added to the existing community of experiments centered on social networking analysis at a big case. The third aspect is that it explores both the topology network and the actions of the performers in the network vast K-pop common networked system of Twitter accounts. Therefore, this research not only takes into consideration the prevalent behavioral analysis of social data but also makes the integrated network layout awareness and behavior that is drastically different from the "straight forward" analysis of a single narrow diagram (Albert & Barabási, 2002; Newman, 2003). The basic research aims of this thesis are as follows:

1. To model a new concept (i.e. K-pop famous twitter accounts) that draws on Twitter users and their Twitter interactions.

2. Determine the main players on Twitter as throughout the internet network the famous K-pop Twitter conversation.

3. To define the grade distribution of Twitter relations in K-pop Twitter accounts.

The following segment examines briefly wider research on social networking and following the methodological framework of this study, how the study is positioned therein, with a brief discussion of the K-pop famous Twitter account. The following segment explains how this sample is conducted and evaluated. The K-pop famous twitter account case SNA results segment accompanies it. The paper continues by analyzing the results and their consequences for utilizing social networking to include not only channels for information communication, but also incentives for stakeholder engagement and exchange.

Literature Review

The notion that there is a mechanism to enable individuals gets to know someone, explicitly and implicitly, is based on a social network. People are becoming increasingly concerned about online communication; as they have never been in so much connect before the invention of internet (Churchill & Halverson, 2005). Over and beyond pure sharing networks or interactive congregations, social media also have grown to be known for their ability to facilitate aggregation. Likewise, knowledge technologies grow further organizational borders to form a part of the broader societal context, which requires research of the competitive technical intelligence network environment and social dynamic systems. Social networking is causing a big difference in how citizens perceive and see their environment (Simos, 2015). Twitter has been showing significant user growth as a micro blogging tool, which began in October 2006 (Java, 1970). Usage with Facebook apps quickly transfers and adopts information (Zhang et al., 2016). Social media literature over recent years is abundant, whereas the concept's agreed definition is less precisely stated (Kapoor et al., 2018). The present study defines online networking as a variety of people that allow interactivity and distribution of knowledge amongst users of accessible channels that encourage them to establish social links with the media networks (Struweg, 2002; Kandadai et al., 2016; Kapoor et al., 2018; Lee et al., 2018; Statista, 2018). Social networking literature has been summed up into 12 clusters. These are the following clusters (Kapoor et al., 2018): (1) Social media applications, behaviors, and implications (2) Social media site analyses and recommendations (3) Social media operational impact (4) Social communication technology (5) Social media participatory (6) Risks to social media (7) Social network usage stigmatization (8) Value creation through web based life (9) Social media during a important occasion (10) Support-chasing through web based life (11) Social media in the open area and (12) Traditional/online networking separate.

Clusters 1 to 8 have certainly provided significant coverage in work on information systems. Cluster 9, as indicated in the introduction, is where this paper was published. Yet it can also be claimed that Cluster 11 overlaps since the case was deemed in this article is freely accessible sector. There has been small research lately in Cluster 12, which might result from widespread social networking recognition outside the mainstream media era.

Social Network Analysis (SNA) is an analysis of human relationships using graphic theory. The viewpoint of the network depends on relationships between actors like those involved in disaster information exchange (Tsvettovat & Kouznetsov, 2011; Samatan et al., 2020). Network research has an essential characteristic (Marin & Wellman, 2011). First, be careful about the relation, not the attribute. Secondly, emphasis on the network, not the community. Thirdly, the requirement for a particular relationship context is meaning context significant. There are numerous Social Network Analysis (SNA) theoretical layers to be conducted, including participant group and device level. Actor Analysis is the centrality factor used for level classification on a whole network. There are four centrality measures that are most widely used namely central, proximity, intercede, and self-vectored. Density, reciprocity, diameter, and distance at the system level, centralization are the most common measure.

The area of social network analysis (SNA), of which this investigation reflects on the connections between the networks and actors and SNA model includes 'relationships and associations, development and associations, and dynamic forces in networks and activities on social media platforms (Struweg, 2002). While SNA has been used in the areas of socio-computational sciences (Wasserman & Faust, 1994; Otte & Rousseau, 2002), recently it is been found in complex fields, economics, industries and medicines (Can & Alatas, 2019). A collection of hypotheses, methods and instruments is often known as SNA (Valente, 2015). It is usually outlined by embedding in three key assumptions (Valente et al., 2015): (1) The nature and characteristics of networks impact system performance (2) The role of actors within a network influences their actions and (3) The behavior of actors conforms to their network context.

In addition, the aim of this study is to make the use of SNA easier (based on graphics) to identify social networks made up of nodes to which actors link with one another by sharing ideas, values, views, human links, and disagreements. This research argues that successful social networks have contradictory effects that can affect human, social, and financial information programs, regulation, ventures, plans, and collaborations (including architecture, implementing, and results) (Serrat, 2010). Social networking thus was essential to the dialogue on democratic society – a forum for popular discussion and conflicts as well as the sharing of ideas. As a public segment, the sharing of social media is as essential as any other broad public gathering. Network charts of digital social networking communications sites such as Facebook will offer insight into the position social media plays in our culture (Can & Alatas, 2019). Such tools and the scale of electronic social media place SNA at the forefront of several problems worldwide. The phenomenon of increasing user behaviors by types in social media enables people to be more linked worldwide than ever before (Zhang & Chang, 2018).

Methodology

Methodological Framework

This volume investigation follows the implementation of a single case study. The topic (K-popular Twitter accounts) is selected in an instrumental case study because it reflects another issue under review (i.e. social network analysis) that may offer an overview of the subject (Ary et al., 2018). Nevertheless, as a case study system, the analytical choices may be called a very loose system and as such are dealt with in a rational way (Meyer, 2001). Therefore, these options are listed in Table 1:

Table 1 Methodological Criteria and Recommendations for this Case
Methodological consideration	Methodological choice
Research paradigm	Quantitative research
Research design	Instrumental, single case study design
Sampling strategy	Case selection
The case	K-pop popular twitter accounts for following in Thailand
Sampling units	5,356 tweets: K-pop popular twitter accounts
Data collection	Twitter Streaming Importer plugin through Gephi API
Data analysis	Gephi social network analysis, Gephi advanced network metrics, and Gephi statistics

This section contains a short overview of the popular Twitter case of K-pop, an outline preceded by Gephi as an SNA tool applied to this questionnaire data processing and data analysis for screening.

The Case: Tweet of the K-pop popular twitter accounts in Thailand

Korean singers induce Korean wave to both the Thai entertainment circle as a whole and to teenage fan clubs by bringing in imitation in Korean physical appearances and apparel, eating taste, and tourism, including their verbal and nonverbal expression. Such Korean wave is influenced by internal factors i.e. a singer's own competence, cultural adaptation etc and by external factors i.e. integrated and various kinds of media and channels planning, besides onstage performance to intensify traditional Korean culture and K-pop culture. Most Thai fandom are 11-29 years old and there are more females than males. Formation of each Korean fandom brings about information exchange, group communication, and group culture through certain symbols, such as colors, group-names, and communication networks for common activities (Suwannapisit, 2008). Entertainment - Perception of Korean wave was not correlated with whether consumers choose to buy Korean-style entertainment or not, types of Korean-style entertainment purchased, and spending on Korean-style entertainment, but was correlated with purchase channels of Korean-style entertainment (Jaiwai, 2014). In this study, we use the ten K-pop twitter accounts as popular in Thailand as shown in Table 2.

Table 2 K-Pop Twitter Popular Accounts in Thailand
Twitter accounts	Followers (K)
https://twitter.com/BTS_Thailand	372.3
https://twitter.com/REDVELVET_TH	86.5
https://twitter.com/NCTZen_TH	73.0
https://twitter.com/MonstaXth_	62.5
https://twitter.com/IZONE_TH	35.0
https://twitter.com/ExoExothailand	34.8
https://twitter.com/MAMAMOO_TH	21.4
https://twitter.com/AB6IX_THAILAND	20.9
https://twitter.com/SNWThai	17.5
https://twitter.com/WOODZ_THAILAND	9.3

Gephi for SNA

In answer to the research issues, this investigation conducted a SNA with Gephi, free/liber software distributed by the Gephi Consortium under the GPL 3 ("GNU General Public License"). Gephi is an open-source visualization and network research program. It uses a 3D rendering system to view big real-time networks and to discover more rapidly. A scalable and multifunctional design provides fresh ways for dealing with diverse data sets and generates useful visual outcomes. In collaborative network discovery and analysis, we present many core features of Gephi. This offers fast and broad links to network data and specializes, filters, navigates, manipulates, and clusters. Finally, we illustrate the main facets of dynamic network visualization by integrating interactive features of Gephi (Bastian et al., 2009). It is a well-organized framework for a workbook made up of multiple workbooks needed to indicate a network diagram. An 'edge list' describes network connections (named 'graph edges') and includes all the network-linked unit pairs. The worksheets often include details on growing clusters and vertex (Struweg, 2002). The interface characteristics of the Gephi program demonstrate various network graphic representations and graphic data features to show things such as form, scale, color, and location (Hansen et al., 2012).

The Twitter Stream Plugin offers more modern technologies to draw on Gephi Basic. The plugin uses the Twitter Stream API and represents tweets as a graph. Three methods of representation (network logic): (1) Full Smart Network: Do a full representation of User, Tweet, Hashtag, Url, Media & Symbol (2) User Network: Do a weighted app to device network of RT and Mentions parallel edges, and (3) Hashtag Network: Keyword weighted to the Keyword network.

This analysis mainly covered network simulation, social network APIs, data import and export features, and SNA.

Data Collection and Analysis

Data description and dispersion

For this investigation, the Twitter details are imported in the range of time 1^st -14^th of July 2020 through Gephi Twitter Streaming Importer plug-in, which moves a question (in this case K-pop popular twitter accounts) to the related Twitter API rather than completeness (Zhang et al., 2020). Gephi restricts that we can only get Twitter messages for fewer than two weeks owing to API restrictions.

The popular Twitter account data from mined K-pop is then accessed regularly into the Gephi template according to edges and vertices. Edges and vertices are the main network theory concepts, which is one of the theories behind this investigation (Banica et al., 2015). First, "links" (such as "links," "ties," "relationships"), are social interactions, organizational structures, physical immediacy, or abstract connections (such as hyperlinks). Secondly, vertices (similarly known as "agents," "nodes," "items," or "entities") may include persons, Sites, activities, societal systems, and contents (such as keyword tags, videos, or websites) (Chae, 2015). From the point of view of network theory, the edge thus connects two social network vertices (Alhajj & Rokne, 2014).

Network structure analysis

Upon the distribution of the popular K-pop Twitter accounts were created, the next step was to quantitatively analyze and view the network structure. The network was visually illustrated with the algorithms of Clauset, Newman, and Moore Clusters and Harel-Koren's Quick Multi-Scale Architecture Algorithm to minimize visibility in the graph (Smith et al., 2014; Lipschultz, 2015). This made things easy to comprehend and at the same time improved the application of structure and analysis (Agapito et al., 2013). The next step in the study of the social network was the measurement of increasing vertical network metrics. The following metrics have been calculated to explain the configuration of the network K-Pop collected popular twitter account data for the purpose of this inquiry.

One of the SNA's main features is that such social networking networks are popular and active 'stars.' This notion of the identification of the important vertices in a graph is based on the classification, which generates the values and in turn is called as centrality (Wang et al., 2010). As the famous K-pop Twitter account network is driven, it needs both the degree and out-degree of centrality to be measured. Similarly, in-degree centrality is defined by the amount of accounts with arrows that lead to either a Twitter address. In this case, the level of popularity is called (Miller et al., 2015). The out-of-degree centrality instead corresponds to the number of twitter arrows. The most sophisticated measurement of the twitter is then pointed as the key donors to the network.

From the perspective of social network theory, the central importance is another central metric that must be considered. A Betweenness Centrality is a function of the frequency of the shortest path between two different vertices has been granted a vertex (Hansen et al. 2012). The twitter with the strongest priority is known as the network bridges. Closity centrality represents the average difference in the social network between a vertex and the second vertex (Struweg, 2002). Presuming vertices that either has communications or execute their current connections (vertices), low central closeness implies that the tweeter is immediately linked to, or "just hop apart" the bulk from the other Social Network vertices (Hansen et al. 2012). Eigenvector centrality explicitly supports vertices with similar vertices (contrary to degree centrality). The eigenvector centrality metric network not only considers the number of vertex contacts (its degree) but also the degree of vertices on which the network is connected (Miller et al., 2015). Finally, Gephi calculates and analyzes the clustering coefficient using an algorithm for group identification resulting in obvious clustering (Clauset et al., 2004). The outcome and the argument of the data analysis follow below.

Results and Discussion

Prevalence and Patterns of K-pop popular twitter accounts

Gephi's advanced 'crawling' of the famous K-pop twitter pages have contributed to 5,356 tweets being extracted. The resulting 5,356 tweet data were "cleaned" by removing tweets that are not relevant to the study's vital tweet relationships. The famous twitter network of mined K-pop accounts contained 10,045 distinctive vertices and 21,248 edges. The edges of this survey featured initial messages, remarks, and mentions. Visualization of the dynamic network provides opportunities to understand changes in structure or content propagation (Moody et al., 2005). Dynamic networks were easily and intuitively explored in Gephi from the outset. The architecture supports graphics with a layout or material that varies with time and provides a timetabled feature that retrieves a part of the network. The program can check all nodes and edges that suit the timeline slice and upgrade the visualization feature. This enables a dynamic network to be treated like a film sequence. The module may be interactive and obtain network data either from a compatible graph file or from an external data source. A data source is able to send dynamic controller network data at any time and display the analysis application test immediately. For e.g., to see the network, a web crawler can be connected to Gephi construct time. The design is interoperable and easy to run and it is established for collaboration with existing software, databases and web services for third parties (Bastian et al., 2009). Figure 1 shows the 'overall diagram' showing the Harel-Koren multi scale layout algorithm (Harel & Koren, 2001) for popular K-pop Twitter accounts. Thus, Figure 1 shows the total networking data of the popular twitter accounts and Table 3 summarizes the overall diagram metrics of the case.

Table 3 Total Metrics of Graph of K-Pop Popular Twitter Accounts Case (Source: GEPHI Version 0.9.2)
Graph type	Directed
Total Nodes	10,045
Total edges	21,248
Average Degree	2.115
Average path length	2.6289647966414
Epsilon	0.001
Probability	0.85
Number of Weakly Connected Components	2
Number of Strongly Connected Components	10,038
Number of iterations	100
Sum change	0.03505722242787635
Modularity	0.694
Graph density	0.000

Influence and Network Analysis Results

This segment focus on the internal networking and the scale of the famous social network of K-pop Twitter accounts. It’s characteristics shows each vertex is dependent on degree and degree similarity, bias and centrality of the function.

In-degree and out-degree centrality results

Figure 2 and 3 represent the in-degree and out-degree centrality of K-pop popular twitter accounts.

The in-degree means the number of users on Twitter responding to or mentioning the popular Twitter accounts of K-pop. Based on the degree of Gephi statistics, over 100 arrows point to the top three vertices. The highest to lowest three most popular accounts included in this survey were: (1) @nctzen_th– an in-degree of 405 (2) @REDVELVET_TH– an in-degree of 246 (3) @UME-- The official Twitter for Universal Music Enterprises, the music catalog for @UMG, @CapitolRecords, @Interscope, @DefJam, @IslandRecords, @Motown&morewith an in-degree of 151. Therefore, the @nctzen_th, @REDVELVET_TH, and @UMEappears to be the most famous in this survey account. The rest of the members of the social network are "in-between" position.

Popularity in a social networking network is not the only indication of effect. The prominent accounts (out-degree centrality) are regarded for the intent of this investigation. Secondly, only ten users were communicating explicitly with @nctzen_th on Twitter. Nonetheless, the highest Twitter handle was @RVsmtown – which emerges as a resident from Twitter's account information. Actually this often means, though, it is an influent site, which is very outspoken and addresses many others of the K-pop famous Twitter accounts debate. Therefore, the authoring account extracts them into links or interacts if they were previously in the network with them for a second time by referring to others. The extent of a Twitter account refers to the arrow total that is on the network or the number of accounts to which it responds. Thus, this is an indicator to focus and is shown in one account for others.

Closeness centrality results

As stated earlier in this article, the centrality of closeness measures determines the shortest paths of all nodes and then allocates a score for every node on the fastest routes. This form of a power station is used to find the people that are best positioned to influence the whole network as quickly as possible. The proximity centrality will also help to identify successful "broadcasters" in a social network. From the 3,301 K-pop popular twitter accounts only 66.92% (2,209) users had a comparable ranking of 1 but 33.08% of the entire K-pop popular twitter accounts ,Twitter users have a main closeness ranking of 0. In this analysis of K-pop popular twitter accounts, consequently, the network may be deduced and still the connectivity is linked significantly in a complex way.

Betweenness centrality results

Figure 4 represents the betweenness centrality results of the K-pop popular twitter accounts inquiry. This calculation shows why famous K-pop twitter accounts serve as 'bridges' to all social vertices connecting the network by defining the shortest of every routes and how much a vertex dropped in one.

For the purpose of the Network, Diameter included betweenness centrality, closeness centrality, and eccentricity, the Fastest algorithm for betweenness centrality (Brandes, 2001). It was applied to display this graph-distance between both node pairs. The information is spreading over quite fast routes on Twitter. Such pages for Twitter on short routes, thus, monitor the dissemination of knowledge through this social network. Therefore, accounts via Email are the significant number of quick paths that are perceived to be essential knowledge gatekeepers. The Facebook page of the highest quality was in the K-pop famous Twitter account event, @nctzen_th, accompanied by @sunflowercharts and @redvelvet the Twitter users listed in the above centrality topic degree. These three apps of Twitter may, therefore, be considered not only the most famous but still the most critical on the popular social network of K-pop Twitter accounts.

Eigenvector centrality results

The centrality of Eigenvector is considered as centrality type of "higher level." A less linked Twitter user might have a really big one central vector with Eigenvector centrality. Nonetheless, no links have been really well defined to enable high variable value connections. This implies that it is better to connect several vertices to others. The centrality ratings in the popular Twitter K-pop survey were significantly low, which implied insufficient evidence that connecting to certain K-pop popular Twitter accounts would be more useful for other social network users.

Analytics and Visualizations

Figure 5 shows the sociogram style as classes. The vertices of the groups by means of a clustering algorithm. There are categories grouped by their relative network density. These clusters help to combine vertical groups (network users) that display high network density. This applies to network customers that are extremely important in-degree and/or out-degree. There are network applications also considered to be influencers of the network. The groups further help network user's cluster with a lower level of network density and ignore as specific cases that do not matter in network analysis. Mostly since, they cannot speak on the network with others. The Clauset, Newman, and Moore algorithms (Clauset et al., 2004) were used for this analysis and visualization to display the connections between these vertices. In this algorithm, modularity as network infrastructure is used to shape a community-distributed network.

The classes have been organized individual boxes to display isolates in the human party. Gephi then measures the clusters according to the criteria used in community selection (Udanor, Aneke & Ogbuokiri, 2016). In the popular case of K-pop Twitter, Gephi generated 19 groups. The sociogram affecting (Figure 5) shows the clusters in separate boxes with links to various clusters across a range of colors. Such isolates do not impact the visualization overall, regardless of their non-network connectivity. This is also why the links in the figure are shown in a revolving way. There should also be a communication between the groups. The main clusters in Figure 5 are focused on the west, with connections to several other social network nodes.

The primary drawback of this analysis may be claimed that it does not have a certain degree of reduced effects. This refers more specifically to the apparent lack of general social networking engagement with the popular K-pop twitter case. This seeming absence of social media attention, especially on Twitter, may have been affected both locally and nationally by several other big news events. While knowledge is overwhelmed, it is a fact that will not change in the immediate future, particularly through social media. This might then offer more study the ability to investigate the spread of social media users, particularly those who influence the person during critical events directly.

Conclusion

Big data on social networking networks are among the most critical, yet some of them remain subject to research. For this inquiry, Facebook, a commonly used social networking site, utilizing K-pop famous Facebook profiles, was used to collect big data. The Twitter pages were chosen based on the majority of the K-pop fandom group in Thailand. This research was focused on graphical and network theory to perform a social network study of the K-pop famous Twitter accounts regional discussion. This culminated in a visual map analysis focused on 5,356 K common twitter accounts of 3,301Twitter users (vertices) showing 21,248 connections with Twitter (edges). The main players in this SNA were @nctzen_th, the fandom, and Thai citizens to a small degree who are inspired by K-pop music. The distributions revealed that the relationships between the ten key K-pop famous twitter accounts were small, as the majority of proximity and centrality were weak. This could demonstrate how well Thai fandom have been involved in pop music in Korean culture which will affect everyone in Thailand. It is obvious from the previous discussions social networking is inherently key to today's society, with broad influence, and which cannot be refuted or neglected. This paper shows how broad real-time Twitter data can be used to gain insight into social networking analytics with visualizations utilizing Gephi and Twitter Streaming Importer plugins. The paper also demonstrated Gephi as a way to utilize massive unstructured data that are mass-produced every day. However, it permits the conclusion of apparently uncoordinated microblogs by employing effective computational methods that can help the company and decision-making regimes. The famous case study of K-pop Twitter confirms further that digital economies are part of the battle of social networking.

Acknowledgement

This research is financial supported by the faculty of humanities and social sciences, Khon Kaen University, Thailand.

Keywords

Optimum insulation thickness; VIP; VIP-PUF combination; Life cycle cost savings.

Introduction

In order to conserve energy and corresponding cost of heating and cooling in buildings, application of thermal insulation on components of buildings in regions of extreme climates has a proven advantage at the cost of insulation (Hasan, 1999). The thickness of thermal insulation can be decided on the basis of life cycle cost analysis that leads to maximum savings or minimum total cost and that is what is known as optimum thermal insulation thickness (Ahmad, 2002;Çomakli & Yüksel, 2003). With the objectives of better efficiency of building envelope, building insulation norms across the world are now demanding higher resistance to be offered by the insulation material, it can be achieve either by increasing insulation thickness or by reducing thermal conductivity of the thermal insulation (Song & Mukhopadhyaya, 2016). In the present time vacuum insulation panel (VIP) is an advanced product in building thermal insulation market with the property of high thermal resistance, but it’s high cost is a constrain in gaining market share (Kalnæs & Jelle, 2014). This paper is an attempt to give a simple approach of combining conventional thermal insulation with VIP as a solution to the problem of high cost of thermal insulation while keeping the minimum space occupancy advantage intact from customer point of view. The implementation of this approach is demonstrated with its application in case of heating of building in cold climatic zone. According to the national building code (NBC) 2005 of India, cold climatic zone is one of the five major climatic zones of the country (Bhatnagar et al., 2019) which is consider for this study. The reason for selection of places of cold climatic zone of India is based on the results of earlier studies that revealed heat losses are large in buildings and thermal insulation should be employed on building envelope components like walls and roof in such places (Bhat et al., 2009; Jindal et al., 2013). For this study Srinagar and Pahalgam are considered as two places of cold climatic zone of India as both are important tourist locations (Bhat et al., 2009) and value of internal spaces in buildings worth a lot, so minimum thickness of insulation with maximum life cycle savings need to be analyze on inner portion of walls in heating application. Burned brick wall is considered in this study comprises of inner and outer plaster on brick of 230 mm thickness which is common in Indian construction practice (Jindal et al., 2013; Kumar & Suman, 2013). Heating degree day values at 18° base temperature for Srinagar and Pahalgam is based on the data of daily ambient temperature since 2003 taken from Srinagar, Rambagh centre of Indian Meteorology department (Bhat et al., 2009) to calculate annual heat losses under quasi static conditions (Cabeza et al., 2010).

The selection of thermal insulation material and its minimum thickness for achieving maximum benefits in terms of life cycle cost savings, minimum total cost and minimum environmental impacts were analyzed by number of researchers from different angles as reviewed by authors (Kaynakli, 2012; Jafri et al., 2015). Hasan (1999) analyzed optimum insulation thickness for external wall by minimizing total cost on the basis of life cycle cost analysis and determined savings over 10 years for polystyrene and Rockwool. Bolattürk (2006) analyzed optimum insulation thickness of polystyrene on the basis of minimum total cost by considering building life of 10 years. The development of any product is directly or indirectly related to the market and which is affected by the cost and services (Avesh & Srivastava, 2019, 2020; Mohd & Srivastava, 2019). With the objective of minimum occupancy of space by the insulation to fulfill the energy conservation building codes norms for U value of building envelope component for composite climate of India, different insulation materials were analyzed (Kumar & Suman, 2013). When it comes to minimum thickness of thermal insulation than VIP can be considered as an option, because of its much higher thermal resistance as compared to conventional thermal insulation materials (Simmler & Brunner, 2005; Song & Mukhopadhyaya, 2016). Alotaibi & Riffat (2014) discussed the state of art thermal insulation material VIP specially silica fumed VIP with long life and high thermal resistivity as an option for future for reducing issues related to internal spaces in heating application, although it’s high cost is a hindrance in its economical acceptance. Alam et al. (2017) reported the economic viability of fumed silica VIP in high rental value nondomestic buildings for places like London on the basis of discounted payback period. Fantucci et al. (2019) justify the economical acceptance of VIP on the basis of life cycle cost analysis with the consideration of savings in space cost. Geng et al. (2021) determined optimal VIP-structural insulation panel thickness by considering aging effect of thermal insulation material by modeling the building in OpenStudio software and further using P1-P2 method for life cycle cost analysis. Gonçalves et al. (2020) also advocated the selection of VIP as candidate thermal insulation material because of its excellent thermal resistance properties and suggested its use in combination with other thermal insulation material for external walls composite system. Berardi and Sprengard (2020) also considered cost of VIP as an economic issue, the solution for which is required as part of future research.

On the basis of the above literature review it can be concluded that there is need to further analyze combination of VIP-PUF on building wall to see weather better life cycle cost savings can be achieve with lesser insulation cost with minimum thickness as of VIP.

Methodology

In order to analyse the optimum thermal insulation thickness on building walls as the minimum thickness at which savings should be maximum in the present research life cycle cost analysis (Al-Sallal, 2003) is used, overall heat transfer coefficient equation earlier derived for combination of thermal insulation materials (Husain Jafri & Bharti, 2018) is used in order to calculate annual heating cost through degree day method (Ucar & Balo, 2010). Further life cycle savings are determined through discounting technique, initial investment is in the form of purchasing of insulation in year zero is considered as negative saving, than the future savings of money as a difference of cost of heating without insulation and with insulation on the walls is converted into present values by considering depreciation of money, optimum value is considered as that value of thermal insulation where this life cycle saving becomes maximum. Table 1 can be referred for nomenclature used in the subsequent analysis.

Table 1 Nomenclature Used in the Analysis
	annual cost of heating saved per unit area of wall (Rs/m2)
	per unit volume cost of first thermal insulation (Rs/m3)
	per unit volume cost of second thermal insulation (Rs/m3)
	cost of energy per kWh (Rs/kWh)
	total cost of thermal insulation material and heating per unit area of wall (Rs/m2)
	depreciation rate
	fraction of total thickness of thermal insulation
	future annual cost of heating saved per unit area of wall (Rs/m2-year)
	heating degree day at 18° base temperature (°C-days)
	heating value of electricity (J/kWh)
	insulation cost per unit area (Rs/m2)
	thermal conductivity of first thermal insulation (W/mK)
	thermal conductivity of second thermal insulation (W/mK)
	life cycle heating cost saving per unit area of wall (Rs/m2)
	life cycle cost saving per unit area of wall (Rs/m2)
	life period (Year)
	present worth of cost of heating saved (Rs/m2)
	total wall thermal resistance without insulation (m2K/W)
	without insulation overall heat transfer coefficient of wall (W/m2-K)
	with insulation overall heat transfer coefficient of wall (W/m2-K)
	thermal insulation total thickness of (m)
	optimum thickness of thermal insulation
	variable year
	period of payback
	Cumulative present value of savings at the end of year just before break even
	present value of saving in year of break even
	heating system’s efficiency

Annual cost of heating saved per unit area of the wall is determined by considering steady state heat transfer condition as given by equation (1) (Bolattürk, 2008; Husain Jafri & Bharti, 2018).

Where

(Husain Jafri & Bharti, 2018)

Further present worth of future savings in any year y is determined by discounting method (Fantucci et al., 2019; Geng et al., 2021) by equation (2)

(2)

Life cycle heating cost savings by installing thermal insulation on the walls is given by the equation (3)

(3)

Life cycle cost savings per unit area of wall with the consideration of cost of thermal insulation is given by equation (4)

(4)

Where insulation cost per unit area of the wall for the combination of the two insulation of different fraction F is given by equation (5) (Husain Jafri & Bharti, 2018).

(5)

In case of without any degradation in the thermal performance of insulation i.e., considering constant thermal conductivity throughout the life period, future annual savings becomes constant and equal to C_AEHS so it can take out of summation sign from equation (4) and modified form of equation (4) is equation (6)

(6)

Where represents present worth factor, which will become constant for a given life period and depreciation rate d.

Period of payback is calculated on the basis of value of year in which first time break even achieve with the formula given by equation (7) (Geng et al., 2021) corresponding to maximum life cycle savings conditions.

(7)

Calculations can be easily carried out on excel sheet for life cycle cost savings for different values of insulation thickness, the same can be represented graphically to determine optimum insulation thickness at a point where savings becomes maximum for considered unit area of the building wall.

Results and Discussion

With the objective of determination of minimum thickness of thermal insulation on building walls to have maximum life cycle cost savings, life cycle cost analysis is carried out for 40 years period with the details of parameters shown in Table 2. Present cost of thermal insulation and energy is considered whereas annual depreciation rate is considered as long-term average for Indian scenario.

Table 2 Calculations are Based on the Following Values of Different Parameters
Parameter	Value
in ?C-days for Pahalgam  in ?C-days for Srinagar	2902.6 (Bhat et al., 2009) 1955.7 (Bhat et al., 2009)
Heating through Electricity
in Rs per kWh  in J/kWh	5.5 3600000 0.99 (Kaynakli, 2008)
Thermal insulation 1- PUF
in Rs/m3  in W/mK (kg/m3)	60,000 0.0251(Geng et al., 2021) 40 (Geng et al., 2021)
Thermal insulation 2- VIP
in Rs/m3 in W/mK (kg/m3)	485715 0.004 (Geng et al., 2021) 210 (Geng et al., 2021)
Overall heat transfer coefficient(W/m2-K) which is reciprocal of total resistance of wall without insulation for wall type2 (230 mm burnt brick wall of thermal conductivity 0.81 W/mK with 0.0127 m plaster of thermal conductivity 0.72 W/mK on both the sides)	2.05 (Kumar & Suman, 2013)(Jindal et al., 2013)
(%)	4

In the first part of the analysis, optimum insulation thickness of VIP is analysed on the basis of equation (6) for F= 0 condition. The variation of life cycle cost savings is shown in Figure 1 according to which life cycle cost savings initially increases at higher rate with increase of thermal insulation thickness and becomes maximum than goes down at lower rate as obvious from slope of the curve and the optimum thickness of thermal insulation is considered as one where life cycle cost savings becomes maximum (Bolattürk, 2008). These results confirm the issue of rate of diminishing returns as observed in earlier studies by increasing the thickness of thermal insulation (Al-Sallal, 2003).

Further in order to see the possibility of getting more life cycle savings and lesser payback periods with lesser investments, VIP in combination with PUF is analysed and it is found that in both the cases use of combination of VIP-PUF leads to better results as compared to VIP only with same optimum insulation thickness which can be also be seen from Figure 1.

For Pahalgam VIP-PUF combination with 3% fraction of PUF and 97% VIP optimum insulation thickness is 0.006 m with slightly more life cycle cost savings than VIP alone for the same thickness for analysis period of 40 years and for Srinagar with optimum insulation thickness of 0.005 m even 14%PUF and 86% VIP combination leads to more savings than VIP for same thickness of 0.005 m as can be seen from Figure 1.

Such results not only lead to increase of life cycle cost savings while maintaining minimum thickness but also reduce cost of insulation as PUF is much cheaper than VIP, so investments can be getting back in lesser time period. Table 3 shows percentage increase in life cycle cost savings, percentage decrease in cost of insulation and percentage decrease in payback periods in both the cases.

Table 3 Advantages of Using VIP-PUF in Combination as Compared to VIP Alone as Thermal Insulation on Wall
Place	Optimum insulation thickness (m)	Percentage increase in life cycle cost saving per unit area= [{(LCS with VIP+PUF) -(LCS with VIP)}/(LCS with VIP]*100	Percentage decrease in Cost of insulation= [{(Cost of VIP+PUF) -(Cost of VIP)}/ (Cost of VIP)] *100	Percentage decrease in payback period= [{(PBP for VIP) -(PBP for VIP+PUF)}/PBP for VIP] *100
Pahalgam	0.006	0.021	2.6	2.35
Srinagar	0.005	0.453	12.27	10.35

Results of Table 3 indicate that percentage decrease in the cost of insulation is greater in both the cases as compared to percentage decrease in payback period. The reason for this pattern can be explain on the basis of two costs involve in the analysis i.e., insulation cost and cost of heating. While PUF replaces VIP for fraction of thickness than insulation cost decreases but heating cost increases because lower resistance is offered by PUF as compared to VIP.

Conclusion

On the basis of the above life cycle cost analysis, it can be concluded that better life cycle cost savings can be achieved by using combination of VIP with PUF as thermal insulation on selected brick wall for both the places i.e., Pahalgam as well as Srinagar. For Pahalgam, combination of VIP and PUF for the optimum insulation thickness of 0.006 m leads to 2.35% lesser payback period than VIP alone.

Whereas for Srinagar, combination of VIP and PUF for the optimum insulation thickness of 0.005 m leads to 12.27% lesser cost of thermal insulation than VIP alone with better life cycle cost savings.

The results of this paper are although specific to the climatic conditions of Srinagar and Pahalgam but this must encourage researchers to analyze VIP in combination with other conventional thermal insulation materials for getting better life cycle cost savings with minimum thickness for other climatic conditions that may give boost to the market of VIP as it can be used in combination with conventional thermal insulation materials with lower investments.

Acknowledgement

Manuscript communication number (MCN): IU/R&D/2021-MCN0001135 office of Research and Development cell, Integral University, Lucknow, India.

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