Home Articles New Standardization in Prefabrication: Future of a Sustainable Housing Industry

Standardization in Prefabrication: Future of a Sustainable Housing Industry

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Fig 1 (b) Prefabricated RC Planks
Fig 1 (b) Prefabricated RC Planks

Author

 

 

 

Ms. Sayantani Lala1, Dr. Ashok Kumar2, Dr. Kishor Kulkarni3
1,3Scientist, Architechure & Planning Group, CSIR-CBRI, Roorkee
2Chief Scientist & Head, Architecture & Planning Group and Efficiency of Buildings Group, CSIR-CBRI, Roorkee

 

Prefabricated construction defines the process, where majority of the standardized structural and non-structural components are manufactured in factories and then assembled together at the construction site [1-2]. These components are fabricated by industrial methods based on bulk production in order to build a large number of buildings in a short time at low cost, along with maintaining the desired quality. Hence, prefabricated buildings are also known as industrialized buildings. The advantages of this technique include faster construction, quality assurance and dimensional accuracy. Although the initial capital cost may be high with the additional transportation costs from factory to site, the building components being of a higher quality than the traditional constructions, the maintenance cost and life cycle cost are minimized over the long run. Also, prefabricated constructions are more sustainable because with the use of prefabrication technologies, it was found in a survey that timber shuttering was reduced by 87% along with overall water saving of 70%, thus improving the energy efficiency by 20% per square metre of construction. In addition to these, owing to the factory-production, on-site damage of materials was reduced and building wastes decreased by 30% during the construction phase [3].

However, there are some shortcomings too in this approach. The connections of the prefabricated components are very critical in building systems and hence, need special attention. Historically it has been seen that the failure of prefab houses was due to poor connection details [4]. In addition to these, the on-site installation of prefab components requires skilled labour, which is expensive. Additionally, design restrictions on the dimensions of components may discourage architectural flexibility. However, with the emergence of open systems and better connections, these shortcomings can be easily overcome in the present times. Despite the fact that prefabrication has been in practice since long, the full potential of this technology is yet to be realized. With the growing population and the pressure of providing accommodation for all, the stronghold of prefabrication in the housing sector over traditional constructions is increasing. It is possible that with the help of this technique, the objective of providing mass housing to all can be achieved economically. Hence it is pertinent, that the technologies be standardized at the earliest, for their appropriate field execution.

History of Prefabrication

The timeline of the first prefabricated building is debatable, though according to popular consensus, the first type of prefabricated construction was recorded in 1850s in UK [5], [6], when a carpenter built parts of a building separately to be assembled at site, known as Manning’s Cottage. However, prefabricated housing in mass scale started only in the early twentieth century, where there was a tremendous need in war-ravaged Europe for reconstruction. However, by the 1960-1970s, prefabricated buildings, as part of Industrialised Building Systems (IBS), had been adopted in many countries including Japan, China, UK, Australia, USA, Thailand, Singapore, Malaysia, Argentina, Netherlands, Denmark, Sweden and Finland [7]. Every country had its share of Large Panel Systems (LPS), which was majorly used for mass housing projects. Synonymous with the prefabricated constructions, the failure of the LPS due to inherent difficulties like non-resistance to earthquakes, poor water-tightness, poor thermal and sound insulation, was perceived as the failure of the prefab constructions [8]. The prefab constructions again revived in the 1980s, with prefabricated modules like facades, bathrooms, balconies, staircases, partition walls in the form of sandwich panel systems, lost-form panels (permanent formwork) and semi precast slabs [9]. In addition to these, traditional houses and school buildings were partially prefabricated with wooden or steel prefab frames in some countries like [10 – 11], which led to the rise in the share of prefab industries in the housing sector. In the last decade, the furnishing giant IKEA, in collaboration with Skanska, a construction company, have entered the prefab market with its modular catalogued home product BoKLok, made of timber for 1-3 people of area 50-75 m2. Originally conceived in Sweden, this product had been exported to other Scandinavian countries like Denmark, Finland and Norway and further to United Kingdom. By the end of 2009, 4000 apartments at over 1000 locations in these five countries have been built [12].

One major shortcoming of the prefabricated technologies over the years is its acceptability among the masses. This may be due to its limited design capabilities and fixed plans, which resulted in identical coop-like housing units in the 1960s in Eastern Europe. These housing units, known by various names, like Khrushchyovka, Plattenbau, Panelak etc. have long been associated with deplorable workmanship and poor living conditions, thus psychologically reflecting a diabolical state of economy. However, with the emergence of open systems, the flexibility of the prefab assemblies to disassociate from the monotony of same building plans has been realized and hence more widely accepted as alternative building practice in the Scandinavian countries.

Prefabrication in India: Past and Present Trends

In India, prefabrication came as early as 1948, when the Government of India established Hindustan Prefab Limited (HPL), a public sector enterprise for meeting the housing needs of people. It employed precast concrete panels to build a few residential, commercial and infrastructure projects, and even envisaged to solve the mass housing crisis through single-storeyed aerated concrete panel houses, under the tutelage of Otto Koenigsberger, the legendary architect. However, owing to failures in the aerated panels, inhibitions of the people and political opposition, the prefab run of India was short-lived.

In the later years, partial prefabrication emerged as an alternative technology in India. Several low cost prefabricated technologies for housing (developed by CSIR-CBRI, Roorkee & CSIR-SERC, Chennai) were used including prefabricated roofing/flooring components like precast RC waffle floor units, precast ribbed RC panels, precast brick panels [Fig. 1(a)], precast RC planks [Fig. 1(b) &(c)], precast concrete/ferrocement panels, precast lightweight panels for wall and roof elements and precast RC channel units [13, 14, 15, 16].

 

However, prefabrication industry in India, had not flourished much. Currently, with the involvement of new private players, the housing sector is warming up to the technology. The Building Materials and Technology Promotion Council (BMTPC), Govt. of India has identified more than twenty alternative technologies during the past two –three years to achieve speed and quality in construction which can be used in the residential sector. Some of these technologies include:

Fig 1 (c) Casting of standardized prefabricated modified RC Planks
Fig 1 (c) Casting of standardized prefabricated modified RC Planks

 

 

 

 

 

 

 

  • Industrialized 3-S System using Cellular Light Weight Concrete Slabs & Precast Columns [15], [13]
  • Pre-stressed precast prefab technology using hollow core slab, beams, columns, solid walls, stairs, etc.
  • Monolithic Concrete Construction System using Plastic – Aluminium Formwork & Aluminium Formwork
  • Waffle Crete Building System
  • Light Gauge Steel Framed Structures (LGSF)
  • Glass Fibre Reinforced Gypsum (GFRG) Panel Building System
  • Speed Floor System consists of suspended concrete flooring using a steel joist.
  • Modular Housing System
  • EPS (Expanded Polystyrene) System, PUF (Polyurethane foam) Panel System, Auto clave light weight concrete panel system, SIP for walls

But these alternatives are not yet accepted by public at large. This was reflected in the PMAY organized for urban areas, during February – March 2019, by Arrucus Pvt. Ltd, with CSIR-CBRI as the Knowledge Partner. The concern of the builders from twelve states revolved around the non-acceptability of the people regarding the use of alternative technologies in the EWS and LIG housing. This could largely be attributed to the fact that the performance of these alternatives during different climates, and disasters, has been empirical and untested. Out of about two hundred projects, only a few builders have preferred some technologies like aluminum formwork and tunnel system to name a few, where 10-15% cost saving was achieved due to the faster construction and reduced formwork.

Affordable, durable, comfortable and energy efficient housing is an important issue in present day India. The Govt. of India has set a target of providing housing for all by 2022, especially for people belonging to Economically Weaker Section (EWS), Lower Income Group (LIG) and MIG. Prefabrication seems to be an efficient solution, the adoption of which will be advantageous in the completion of the huge number of houses in the limited time. However, in order for prefabrication to be used in the construction of mass housing, standardization of its various components needs to be completed first. There seems to be paradigm shift now, given a basket of choices to the customers, and if more standardization and flexibility in the precast construction can be introduced, it will create bigger demand for the precast building components in the affordable housing sector.

Importance of Standardization

Standardization is the process of implementing and developing standards for products or technologies to maximize compatibility, interoperability, safety, repeatability and quality, based on the consensus of different concerned parties, in order to facilitate the commoditization of a custom process. Research studies carried out in CSIR-CBRI, Roorkee have recognized that economy can be achieved through the concept of standardized plans (designs) and layouts along with the use of precast elements in buildings. In order for prefab technologies to be implemented, standardization of the following parameters needs to be done:

  • Standardization of dimensioning to promote flexibility of usage of prefab technologies
  • Standardization of building plans
  • Standardization of modular building components
  • Standardization on allied services
  • Standardisation of thermal properties of prefabricated technologies

Standardization in Prefabrication

The objectives of standardized prefabricated technologies can be summarized as to:

(i) Encourage designers to use recommended dimensioning system in the designs
(ii) Facilitate and provide architects / engineers with the most essential design data, guides, and standard checklists while adopting standardized prefab building components
(iii) Promote the wider use of standardized designs, and precast components
(iv) Ensure that the construction industry moves away from in-situ labour-intensive construction to factory-produced precast construction methods to improve quality of construction
(v) Provide people from different income groups, choices / basket of standardized designs and precast components conforming to Indian standards, for different regions of the country.
Hence, the process of standardization can be broadly classified under the following heads.

Standardization of dimensioning to promote compatibility of prefab technologies

In prefabrication industry, the open building system is defined as the process where each component comes from different manufacturer, with free competition between contractors and suppliers and where there is flexibility in design requirements according to the need and want of the client [18]. In this connection, modulus system, where dimensions and spaces are chosen in multiples of a prefixed pitch to promote series production of components [19] is used. In order to standardize components in an open building system, a common set of dimensional rules, known as modular coordination has been adopted in various countries. The basic unit 1M = 100mm, and components are produced in multiples of M, called multi-modules (3M, 6M, 12M, 15M etc. for floor panels) and sub-modules (M/2, M/5 etc. for wall panel thickness) [4], to reduce dimensional variation of the prefab elements. One such example of Open system is the BES system of Finland, based on this modular coordination concept, with a basic design unit as 12M [4]. This system of fixed dimensioning, per se, can be ratified in India, where all the prefab technologies would follow the modular coordination dimensioning system. It has been noted that the market share of industrialised buildings where open systems are in vogue, is larger than where closed systems are used, for obvious reasons of flexibility and transparency [20].

Fig. 2 showcases a schematic plan by using the concept of modular coordination for precast RC Planks and Joist system as flooring / roofing components. Fig. 3 showcases one another open system W-70 of Poland, following a fixed dimensioning system, whereas Fig. 4 shows prefab elements compatible with flexible plans of building.

Standardization of Building Plans

Similarly in India, flexible plans according to the requirements of different geo-climatic needs of the country with various essential attributes needs to be recommended for prefabrication to be adopted widely. The following steps may be followed in order to standardize the different building plans. Firstly, all the prefabricated technologies like frames, panels, etc, are made to conform to a common system of dimensions. Secondly, building plans are envisaged in the same dimensioning system with the following essential attributes such as:

 

(a) Space efficiency, depending upon the requirements of each income group,
(b) Climate responsiveness, reflected in incorporating the traditional knowledge of architecture and suitable materials for a particular geo-climatic zone,
(c) Energy efficiency by optimizing the orientation, window-wall ratio (WWR) or window-to-floor area ratio to ensure sufficient daylight integration, thickness of walling / roofing assemblies for improved thermal performance in buildings, and
(d) Disaster resiliency by selection of the prefab technologies in the construction, with specific characteristics like earthquake-resistance, fire-resistance etc. conforming to NBC 2016 [21] and other IS requirements. Fig.5 shows the process of standardization of a particular building plan.

Lastly, in order to ensure the acceptability of the standardized plans, the internal partitions can be designed suiting to the changing socio – requirements of the society and the flexible living space, can be inter-changeably used for different purposes, as shown in the flexible building plan in Fig.6 (a), (b), (c) & (d). In this way, both standardization and flexibility can be maintained in building plans / designs, materials, and technologies.

Fig 5 Flowchart showing standardization of a building plan with the essential attributes for mass housing
Fig 5 Flowchart showing standardization of a building plan with the essential attributes for mass housing

 

 

 

 

 

 

Standardization of Modular Building Components

Typified standard modules of structural and non-structural building components like stairs, sunshades, doors, windows, bathroom pods, balconies, precast facades and even foundations etc. should be designed in congruence with the standardized plans described previously, in order to reduce the site-intensive construction process [22 -23]. The prefab units or ‘modules’ can, therefore, be transported and assembled on-site, in both traditional and prefabricated construction. Such examples can be extensively seen in the construction industry of Hong Kong [9]. Examples of partial prefabrication or modularization are also present in Indian markets in the form of precast RC planks and joists for floors and roofs of buildings, as mentioned in the previous section.

 

Fig. 7 (a) shows typified standardized door designs and 7 (b) shows casting of a typical precast sunshade for a window size of 1200mmx1200mm.

The efforts are further going on to develop new precast systems using concrete and steel and improve the existing systems for value addition suiting to the present day requirements at CSIR-CBRI.

Standardization of Allied Services

The materials and technologies used in prefabricated buildings are intrinsically different from the traditional constructions. Hence, the provisions for building maintenance and allied services which are applicable to current practices of construction might not be compatible with the prefabricated houses. For example, if the wall panels are made of sandwich insulated panel (SIP) technology, the laying of drainage conduits by chipping off the material can prove to be fatal to the building. Hence, it is essential that proper organization of execution steps be prescribed in the prefab technology installations. The same principle is applied to the fire rating of the prefabricated houses, which might have different resiliency than that of traditional construction. Thus the same fire rating protocol cannot be applicable for both types of construction. Hence, there is a necessity to standardize the allied components like repair and maintenance, fire resistance, water proofing and MEP services conforming to NBC 2016 [21] or other standards provisions, guidelines and applicable standard checklists to be used during the prefabricated constructions.

Standardisation of Thermal Properties of Prefabricated Technologies

At present, building energy and environmental performance is an important area for sustainable and green buildings. It is also valuable for analysing and predicting thermal comfort, energy efficiency and associated CO2 emissions. Therefore, it is essential to have a complete inventory of thermal properties of materials / products, which are compatible for use in the Indian market. Thus, there is a need of standardization of the thermal properties of the prefabricated technologies, which can be used to better predict the environmental performance of the buildings and quantify the sustainability of the technologies in the long run.

 

Way forward

The success of prefab technologies in India will depend upon the concerned parties, namely the GoI, research organizations, contractors and builders by actively promoting and working on its standardization in the housing sector. In connection to this, CSIR-CBRI has developed typology building designs for EWS and LIG suiting to NBC 2016 [21] and IS: 8888 requirements [24]. A set of 25 EWS and 25 LIG plans has been designed by the authors and are in the process of standardization. A number of modular components have also been planned, including doors, windows and sunshades. Apart from common knowledge, numerical analyses have also been employed to validate the best suited standardized components. For example, the design of sunshades (louvers) for critical horizontal and vertical solar angle (horizontal and vertical louvers as per window sizes for different climates) was based upon the sun angle and parameters such as: i) Solar altitude at intervals during peak heating season Jan 16 (30°); ii) Solar altitude at hourly intervals, when the heating & cooling seasons swap, – April 15 (60°) and Sept 1 (59°); and iii) Solar azimuth, the angle of the sun in relation to south at any given time, which would be compatible with the standardized building plans. CSIR-CBRI also has unique test facilities to estimate the thermal properties of materials/prefab technologies and have several inventories readily accessible to academicians, officials, students and stakeholders.

A number of hindrances can be identified in the standardization of prefabrication technologies. For any technology to be appropriated, it has to be modified according to the specific conditions of the applicable country. Most of the prefab technologies which are available in the market have its inception in other countries, with different geo-climatic and social conditions. Thus, they should be modified according to the Indian needs. Secondly, the aim of adopting prefabrication is to improve the sustainability of the construction section. Hence, the path of each and every material and process involved in prefabrication should be checked according to its cradle-to-grave efficiency, thus minimizing the generation of construction &demolition wastes. CSIR-CBRI, Roorkee is working extensively on both these goals, to identify and modify suitable prefab technologies for India along with standardization of plans and layouts for different economical groups. Finally, the policies of GoI should incentivise the use of prefabricated technologies in green-field construction, to help promote its acceptance among masses.

Conclusion

Prefabrication is not a new concept, and has been prevalent in many forms since centuries. In modern housing sector, prefabrication has been in vogue since the early nineteenth century. However, its integration in the construction sector has often failed due to the haphazard method of adoption, impromptu sporadic constructions and non-standardized rigid designs. An attempt has been made in this article to understand the importance of standardization for the acceptance of prefabrication as an alternative construction method in the housing sector. Only standardized streamlined approach will help in the prevalence of prefabricated technologies, where efficient and sustainable processes can help in fast construction of houses. Prefab technologies will be particularly useful in difficult terrains and harsh weather conditions, where traditional constructions of masonry and concrete are often disadvantageous and time-consuming. Thus, only a true balance of prefabrication and conventional in-situ practices, suitably applied in the construction of houses, can help build a sustainable housing industry in the future.

Acknowledgement

The article forms a part of the ongoing R&D Program of CSIR-CBRI, and is presented with the kind permission of the Director, CSIR-CBRI, Roorkee. The authors acknowledge the help extended by Sh. Seeraj Alam, Sh. Ashutosh Singh and Ms. Sukriti Goyal in preparing the drawings and in being indispensable parts of the ongoing project.

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