The Impact Of Modular Construction On Sustainable High-rise Building

Research topic - Modular Construction: Sustainable delivery system for high-rise buildings.

Research Question - Does prefabricated provide the opportunity to deliver sustainable delivery systems?

Prefabrication has been considered broadly as a method of sustainable construction regarding its effects on the protection of the environment. One significant feature of this perception is the effect of prefabrication on the subsequent waste handling activities and construction waste reduction, including waste disposal, recycle, sorting, and reuse. The installation of the modular structures is known to be eco-friendly, safe, and cost-efficient. The analysis of the development of modular building construction in China (T30 Hotel), New York (32) Storeys, and London (Paragon) prove that these countries have great familiarity in the establishment of the modules of 3D reinforced concrete (Furuto, 2012).

This section reviews the outcome of the trends in modern high-rise construction by evaluating image, economic, technological, engineering, and architectural factors that have been noted during the construction or after the construction process of these modular structures in China (T30 Hotel), New York (32) Storeys, and London (Paragon). The major impacts of modern high-rise constructions are also identified as well as the economic issues resulting from the construction of these high-rise structures especially on the residential function (Generalov, 2015).

Structures of prefabricated steel have certain noticeable benefits such as the environmental protection, industrial production, and rapid construction. It has been noted that the prefabricated structures are more appropriate for low-rise structures and their application in the high-rise structures are very rear despite these modular structures having been applied in numerous states globally. The section reviews the results based on the case studies of China (T30 Hotel), New York (32) Storeys, and London (Paragon) T30 by majorly focusing on a particular building method and have considerable amount of information regarding waste factor of these prefabricated modular high-rise steel frame building with diagonal braces which is new category of steel building prefabricated (Generalova, 2013).

The T30 Hotel modular structure in China was implemented by the Chinese construction industry so as to save the country from the dilemma of poor efficiency, high energy consumption, and high pollution. The modules are made from numerous 2D panels starting from the floor cassette to which the ceiling panels and four-panel walls are attached. The structural components were manufactured in factories so as to minimize the welding processes and installation process carried out on the site (Crawford, 2012). The T30 Hotel structure constructed by the BROAD Group is a prefabricated assembled steel building which was erected by manufacturing the windows, doors, cassettes, roofs, and walls in the factories and then sent to the construction site to be assembled (Zhigulina, 2014).

Benefits of Modular Construction

Some of the advantages attained by this modular construction in China include sustainability, good quality, affordable, efficient manufacturing, fast construction, and low-carbon energy (Fetters, 2012). The prefabrication of T30 Hotel was considered as the major strategy of effective wat of minimization of the construction waste. This is because of lower dependence on the conventional technologies of construction such as plastering, tiling, reinforcement, timber form-work, bamboo scaffolding, and cast-in-place concrete (Zhdanova, 2015). The figure below shows the material flow of the T30 Hotel:

Figure 1: the Material flow of T30 Hotel (Yuan, 2013)

There was numerous prefabrication performed in this structure during laying of foundation and the prefabricated structure shows numerous benefits such as low generation of construction waste, low maintenance costs, low construction cost, and magnitude 9-earthquake resistance.

This housing project is made of culminating 18 stories, range of 4 stories, 1060 accommodation units, and 5 housing blocks. The entire construction at the site took 22 months which is 12 months less compared to the traditional construction. The construction waste management performance refers to the general performance comprising four attributes such as illegal dumping, public landfilling waste, landfilling waste, and reuse and recycles waste. These features cover all the perceptions of the final construction waste disposal management activities. The balconies can be joined at the terminal posts of the modules or the loads can be transferred directly to the ground surface. Integrated balconies within the modules can be issued by conveying the end wall of the balcony within the module configuration (Ramaji, 2013).

The time and cost benefits of the modular structure may eliminate completely the option to use the modular technology or erode with more complicated architecture. The optimum application of modular structure can be attained through designing the MEP intensive residential units and hence more expensive sections of the structure in the modular form and the more open space of plan as a portion of a consistent structural frame in concrete or steel (Xiaodun, 2013). The prefabricated steel members exist in numerous sections and sizes and it is the duty of the project engineer to determine the sections and sizes of the steel members which are majorly standard sizes from the manufactures of steel so as to accommodate any architectural design. The process of steel construction is simple and the prefabricated structures of steel can be supplied to the construction site by the manufacturer before being assembled by the use of welding methods or bolts. Majority of the steel structures use the steel as the primary structure known as the building skeleton and the other sections can normally be constructed using other materials such as concrete, panel, and glass (Yuan, 2013). The figure below shows the effects of prefabrication on the construction reduction of Paragon – Bretford:

Economic Issues and Sustainable High-rise Building

Figure 2: Effects of prefabrication on the construction reduction of Paragon – Bretford (Shen, 2009)

The constriction, engineering, and architectural selections are the decisions that comprise how the 32 Storeys in New York was constructed and designed. The space condition, plumbing and electrical systems, control and installation, building materials selection, construction techniques, and material selection are all analyzed in the waste management of this prefabricated structure. The 32 storey provides an important opportunity for market penetration, LEED certification, economic opportunity, and environmental stewardship in this state. The environmental control, optimal construction condition, and material handling during the process of construction of this structure also contributed to attaining LEED credits (Smith, 2010).

It is difficult to identify specific criteria of LEED which favours the modular construction since all the prefabricated project are different and the extent of modular construction and other decisions may alter the level of certification. The 32 storeys in New York provides numerous opportunities to improve the sustainability of the structure during the process of construction and maintaining superior performance within the structure completed (Tatum, 2009). The table below shows the differences in the waste usage, materials and the processes between the 32 storeys in New York and a typical traditional building:

	Traditional Structure	32 storeys-New York
Waste	Construction waste is reduced from 10 to 15% in a factory environment	Construction waste is substantially reduced to less than 5% in a factory environment
Materials	Easy assembly and disassembly process since mortar is used	· Easy assembly and disassembly process since the components are joined by rivets, bolts, and fasteners. · No mortar is used · The components of steel can easily be recycled and also metal façades such as slates timber, brick slips, zinc, and aluminium.
Energy conservation	· Low energy conservation · Low thermal performance of these structures	· Insulation and acoustics benefits the structure by conserving the energy · High thermal performance and air-tightness due to fabrics

The decision to use modular construction should be made from the onset of the design but there are few instances when traditionally designed projects are later changed to modular building. The prefabrication process of the whole structure depends on the heart of the modular structure so as structures with open spaces is not the best structure to use. Apart from the customization of the finishing as demanded in the majority of house projects, maybe probable and will produce very similar costs as traditional site constructed customization. The structural systems of a high-rise structure is a mixture of its horizontal and vertical bearing structure which provides stability, strength, and rigidity of the structure together (Okudan, 2010).

The major precedence in the construction and design of the high-rise structures is to make sure that their rigidity, stability and strength by taking into considerations the impact of important forces in the wind overpowering the uneven shortening of vertical constructions from columns and walls concrete reinforcement under the impact of the load.  In high-rise structures, the materials such as concrete and steel are majorly used. The rigidity of the construction skeleton assist in flexibility and sustaining the wind loads so as resist fluctuations is the seismic activities. In the facades of the current skyscrapers, majorly polymers, aluminium, light curtain panels of darkened and transparent glass, and steel profiles (Parker, 2013). The concrete system is one of the most common construction materials to assist in increasing the strength of the formwork at the site of construction.

Optimum Application of Modular Structures

Concrete is normally used as the major materials for the construction of structures such as floor slab, columns, and beams. The precast construction is one of the most common methods of prefabricated concrete construction. Precast construction is the process of casting the components of concrete offsite in a plant and then transporting them to the construction site for the purposes of assembly. Concrete has good compression strength and there are numerous instances when the concrete is reinforced so as to increase the tensile strength (Zhdanova, 2015). The major shortcoming of the modular constructions is that these structures have limited prefabricated houses since it may be difficult to for the combined modules to form bigger or higher rooms especially when such design cannot be made by the current shapes and heights of the modules. It is only cost-effective to make only the prefabricated walls. The ceiling and walls of the modular structures have the fire resistance of only one hour compared to the brick houses which have the fire resistance of 2 hours since both the brick and concrete are non-flammable (Blengini, 2009).

The prefabrication of the whole room depends on the heart of the modular structure hence a structure with open expanses is not the best structure to consider. The nature of the high-rise structures is such that the modules are clustered around stabilizing or core system. The specific features of the selected modular system have to be understood well by the design team during early phases so that there is conformity of the detailed design to the limits of the specific system, specifically the design’s structural integrity. The design of the high-rise structures is greatly determined by the services, fire, and structural requirements (Vavilova, 2014).

The modular system is the most complete system of prefabrication in the construction which has been built at a factory and then transported to the site of construction for assembly. The modular system non only gives the entire exterior cover such as the roofs, floors, doors, windows, and walls, but also is accompanied by fixtures such as toilets, interior finishes, and mechanical systems. It is popular to see the whole finished modules for the residential structures that have all the rooms like toilets, kitchen, living room, and bedroom joined to it, but the specific sections of the structure such as kitchen and toilet are available as modular. Normally, the units are manufactured in a factory and then conveyed to the construction site where the workers use huge cranes to lift up the units and then stag them in the required position (Pullen, 2011).

Conclusion

The modular construction is introduced to be a resource efficient and materials efficient construction with fast construction, less material waste, re-usability, and less site disturbance. The establishment of the modular structures can not only improve traditional construction industry into industrialized and standardized manufacturing company, but also drive new building materials in construction, new methods of construction, and new systems of building the architecture which is important for the sustainable, escalation, and transformation development of national economy. Since the bulk of the work is carried out in the factory, it is easier to control the safety of the construction site. There will be a reduction in the working on the outdoor overhead since the majority of the constructions end in the manufacturing companies (Zhigulina, 2014).

The process includes the doors and windows installation which are also prefabricated units. Modular contractors manufacture structures at the off-site location or in a factory. They may also work as projects contractors, finishing the structure, site work, installation, and delivery coordination, or modular contractor whose responsibilities are to installation, delivery, and construction of specifically the modules and the general contractor whose is responsible for the whole project (Shen, 2009). The fabrication of this structure, the concrete waste was reduced by approximately 51% to 60% and the construction wastes from the use of timber framework were reduced by approximately 74% to 87% by the use of steel formworks (Thurakit, 2014).

Majority of the wastes in the projects of traditional construction are produced by the process of concreting and the wet trades related, which constitute more than 80% of the wastes in the construction site. The reworking of the concrete which needs work extension, removals, and replacement of work previously completed may also result in wastage in the construction wastage. Other techniques such as the design structure matrix technique and environmental management system, have been put in place in this structure to assist designers in analyzing the impact of precast techniques on the reduction of construction waste and the visualization of this complex construction design process. The prefabrication of T30 Hotel has resulted in a structure with reduced construction waste, numerous activities of waste handling such as disposal, recycle, reuse, and waste sorting which are much more effective compared to the traditional structures (Vavilova, 2014).

The modular structures also have a tendency of accumulation of heat compared to the timber houses which are much lighter hence cool down quickly. There is a need for heating the house during the day and then switching the heating installation at the night. The brick houses have a higher lifespan compared to the modular structures. When constructing the modular structures, there is a need for including the cost of land in the investment since it is difficult to divide the land into slots during the construction. The modular structures are also characterized by smaller rooms despite the homes being large since a piece of modular homes cannot be long or big due to transportation problem (Yuan, 2013).

The construction process generally occurs indoors away from the advanced weather conditions which may destroy the construction materials and enabling the workers to work in comfortable conditions. In the modular construction, while the site work is occurring at the construction site, the modules are also being assembled in the factory at the same time or at some instances the modules are assembled before the on-site construction process begins. This promotes earlier occupancy of the structure and also a much shorter period of construction hence minimizing the supervision cost, financing, and reducing the labour. In the traditional onsite construction, there is engineering of modules and more coordination before the completing of modules construction. There have also been some noticeable changes in the modular manufacturing factories such as their evolution to accommodate the technique of fast-track construction and modern methods of construction delivery (Smith, 2010).

The wastes of construction reduced substantially from approximately 10% to 10% in the traditional structure sites to less than 5% in the environment of the factory. It has been approximated that this type of structure can attain the highest level of reduction of waste compared to both any other technique of modern construction such as pre-fabricated pods or panelized structures and the traditional construction. Majority of the wastes in the projects of traditional construction are produced by the process of concreting and the wet trades related, which constitute more than 80% of the wastes in the construction site. The wastes from the concreting process are generally from both spilt and surplus concrete, steel from cutting of reinforced bars, and direct work. The reworking of the concrete which needs work extension, removals, and replacement of work previously completed may also result in wastage in the construction wastage (Vavilova, 2014).

With units of modular steel, the roof and wall frames were constructed by the use of track and stud method of connection, whereby sections are combined together by the use of rivets, bolts, and fasteners. Subsequently, at the termination of the lifecycle of the structure, the components can easily be disassembled. The ceiling and floor joists have service conduits in the form of holes which permit the running of pipework and cables that can be removed easily. The components of steel can be recycled and the metal façade materials such as slates, timber, brick slips, zinc, and aluminium are also recyclable. Insulation and acoustic benefits of a modular structure are huge as a result of the additional materials used in the erection (William, 2009).

Numerous manufacturers approximately that 10% to 25% extra structural materials are utilized in a typical process of modular construction. The net construction materials used in the modular structural is only slightly less compared to the total building materials in a conventional onsite structure. The thermal performance and the air-tightness of the fabric of the structure are much higher because of the tither tolerances of the joints that can be attained in the environment of the factory which minimizes the requirement for the higher expenditure of utility. The efficient application of materials with lightweight and the minimized waste denotes that the embodied energy of the materials of construction is reduced significantly. The factory and site safety is improved greatly and it is approximated that the accidents reported are minimized by over 80% with respect to site intensive construction (Xiaodun, 2013).

After the architect has finalized the design of the modules, the plans of the construction should be conveyed to the modules manufacturing factories where the greater percentage of the structure is erected. Any other thing from mechanical systems and walls to carpet and painting can be finished on the line of assembly. After the completion of modular structure manufacturing, it is normally not feasible to ship modules extremely far as a result of road load or size restrictions. Once the modules are ready, they are transported to the site of construction and then assembled together. The installation of the modules involves interior finishes, exterior finishes, and connections for MEP (Tatum, 2009).

The steel bars can be used to reinforce the concrete so as to improve its tensile strength by pouring the cement on the top of the tied bars at the site of construction. There have been concerns regarding the transportation and weight when using precast concrete since it is heavier compared to the steel and wood. The panel system is also one of the most popularly used methods of prefabrication of construction in the country since about 43% of the structures in the country use the light panel system. Panels are planer components used to construct structural interior partition, enclosures, non-load bearing, load bearing, roofs, floors, and walls. Steel panelization and wood panelization are the two names used in describing the light gauge metal frames walls or framing of light woo produced in a factory (Zhdanova, 2015).

The final stage of construction involves the completion of exterior systems such as roofing and cladding components as well as the internal surfaces such as elevator shafts, stairwells, and lobbies. There are cases where the modules are sealed with waterproof materials temporarily to sustain weather conditions during the process of transportation. The most expensive section of the installation process involves the use of cranes accounts for daily cost as well as the road closure details. Therefore, there is a need for planning carefully to prevent idling of the crane. The decision to use the modular structures should be made from the onset of design. There are some cases when the conventional site constructed designed plans are later being changed to modular structures (Thurakit, 2014).

One of the noticeable signs of the modular construction is the sustainability compared to the methods of traditional construction. The process of constructing modular structures can prevent negative impacts to the environment on the sites of construction. After the structure has served its purpose, the modular structure can be disassembled and then the modules be relocated for new applications with less wastage of the materials since the majority of the materials will be recycled and protected from contaminating the environment. Another benefit of the modular structures that cannot go unnoticed is their good quality since these structures are constructed through standard production by the use of materials of high quality in the manufacturing factories (Bilec, 2008).

These standard quality structures can avoid effects of severe conditions of weather and inferior materials in the quality of construction as far as possible, while the quality stability and quality of construction are guaranteed by the industrialization production means, modernized inspection approaches, and standardized measures. The cost of construction of these modular structures is also known to be affordable since the cost of modular structures can be regulated through the fast construction process and not by minimizing the material quality utilized in the construction process. The structures used in the modular construction also have efficient manufacturing compared to the methods of traditional construction since the modular construction methods can attain a faster rate of construction (Lawson, 2009).

This is because, with the current modular construction method, rafters, ceiling, floors, and walls are all manufactured in the same factory at the same moment and then transported together to the construction site to form a module. The modular construction process also ensures a faster construction process since there is the simultaneous manufacturing of module and site construction. This reduces the duration of construction greatly since the assembly process of the modules is streamlined with the process of construction. The modular structures can attain reduced carbon emission of 51% and energy saving which is more than 47% compared to the traditional residential construction process (Generalova, 2013).

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