The UK’s construction industry is dynamic and has adopted different house design models due to many factors including new requirements for sustainability, thermal and acoustic performance and environmental impacts. The need to conserve the environment while at the same timed improving the social characteristic of the built environment have direct impacts on the choice of constructional system. This paper explores the modular construction system used to construct a residential apartment in the neighborhood.
The UKs construction industry is advanced in terms of construction management and related construction dynamics. In this paper we are going to explore the construction necessities for a low- rise, short-span residential buildings.
One of the houses chosen in this scenario is my current school term residential building. The house is build with steel and composite materials. This is because steel use in residential buildings provides the much needed high quality, high energy efficiency, rapid construction time and finally satisfy the Code of Sustainable Homes.
Modular construction has 3D or volumetric units spanning the size of a room while a group of modules can be arranged to provide a stable building form. Modules are designed to resist horizontal loads for buildings having more than six storeys. In this scenario and additional braced core were added in some places while a concrete core was added to provide stability to a group of modules.
Loads were tied together at the corners so that loads can be shared between them both in normal conditions and in extreme cases of lack of support from the underneath.
The project comprises of module construction systems many with open sides such that two modules could be placed side by side to give a wide room area. The project has 4, 5, 7, and 12 storey heights with a total number of 827 modules. The 17 storey buildings have 413 modules. A typical module measures 12 m x 2.8 m but some were designed to 4.2m to accommodate motor vehicles.
The house is an apartment building build using steel structures. The houses referred as the Paragon comprises of 800 en suite student rooms, 114 en suite studio rooms, 44 one bedroom and 63 two-bedroom workers apartments. The one and two bedroom houses were constructed using two or three modules, each having 3355m2 floor area.
The modules utilize light steel C sections in the floor and wall area with square or rectangular Hollow section posts used to resist the vertical loads. The posts are 80 x 80 SHS or 160 x 80 RHS and have varying thicknesses depending on the building height. The posts are strategically placed to fit within the light steel wall panels. The edge beams utilize 200 x 90 hot rolled Parallel Flange Channels at the floor and 140 x 70 PFC at ceiling levels to give a partially open sided module of up to 6m span. The floor and ceiling depth has a combined width of 400 mm while the walls have a combined width of 290 mm. The construction has an excellent airborne sound reduction of up to 60Db and a fire resistance of up to two hours.
Modules are connected to each other and to the concrete core using steel angles fixed to channels cast into the concrete core. The forces in these connections are as a resultant of the study of wind forces and the structural integrity. The slip cores were constructed in advance of the modules installed. In other cases, the modules were placed on a steel framed-podium to permit vehicles access to create room for vehicular access to the basement level.
Fig. 1 Module attached to concrete core
Fig. 2 Modules installed on steel podiums
The principle roof system designs required are those of weather-tightness, thermal insulation and air-tightness. Roofs can be designed from steel in the form of roof trusses, purlins, composite panels, and roofing sheeting with insulation.
The roof in this scenario was made of R-32 insulation roof trusses and a 25-yaer fiberglass shingles over light steel frames. The light steel elements are self supporting and can be used for roof top extensions. This results in a light-weight building. In this method, both fire resistance and physics requirements are easy to meet by using layers of gypsium board. Heat losses via the outer walls are minimized by using an insulating material such specifically mineral wool. The floor was added a gypsium screed to minimize vibrations.
The windows are made of thermal pane vinyl double hung high performance glass with screens and raised panel solid Oak cabinet.
Fig. 3 Interior of the building
Functional Performance characteristics
Insulation and air lightness standards in modular buildings are improved thereby utilizing low levels of continuous heating through energy efficient heating strategies. As the average temperature requirements increases the desire for mechanical and air conditioning systems increases. This saves considerable energy in form of wall insulation to keep interior spaces at the required temperature.
When using light steel framing, insulation is normally placed externally to the light steel elements and is supplemented by additional mineral wool between the wall studs.
The use of steel frames in modular building design is economically viable. Steel provide unlimited building height thus, any height can be achieved as well as the designs are made properly. Likewise, podium level creates an open plan space and car parking below. This design is economical in terms of space. It is suitable in terms of residential and commercial use.
Steel provide another advantage in terms of conventional fire protection. Intumescent coatings are used in order to preserve the dimensions of the steel coatings and at the same time provide maximum fire resistance. Square hollow section columns are preferred and advantageous.
The modular model is faster in construction than other modes of construction. Specifically, it outpaces other types by 60% because of lack of site-intensive construction.
In addition, it provides improved quality due to off-site manufacture of steel frames. The use of double skin walls and floors provide e3xcellent acoustic insulation and hence low energy requirements.
In this case, open sided modules were used in the construction process. This provided economy of scale in the manufacture of repetitive modular units.
Sound insulation is effective in the design of all buildings and is essential for comfort and well-beings especially for students. The walls and floors are separated and each unit has a airborne sound insulation of 60 decibels as well as fire resistance of up to 2 hours.
The building is compliant with the Code of Sustainable Homes level three. It is also compliant with the minimum operational carbon emission targets under the Building Regulations Part L1A.
For instance, the choice of light steel walling and roofing systems score an A+ because of the light environmental impacts compared to heavyweight materials such as concrete or blocks.
Acoustic insulation is maintained at 6 decibels and this is better than the Building Regulations Part E. High levels of insulations is achieved by composite floors and use of double layer steel separating walls.
Waste management is controlled in off-site steel manufacture. Waste in steel manufacture is recycled in manufacturing process and this eliminates site wastes.
Off-site steel manufacture significantly reduce local disturbance during the construction process. The Considerate Construction norm is adhered to by considering the impact of construction on the neighborhood and sourcing readymade steel materials away from the construction site.
As a relatively new construction technology, modular homes are the preferred models in the housing industry. The parts of a modular building are assembled in the factory and modules are installed by cranes on the conventional basements. The production of modular homes ranges from 32,000 and above per year and represents 10% of the single family and low-rise multi-family homes. The buildings are considered superior in quality than the conventional homes. The modular building is expected to last for decades before any major repairs are conducted. The controlled environment of modular homes minimizes the risk of delays and error due to poor weather.
Concrete framed buildings are found to use more energy consumption and environmental impacts than concrete structural-frame buildings. The different features of a modular HOME, 2X6 stud framed structure, air tightness, and short construction period provides a host of advantages in construction quality, time, productivity, and efficiency. A lifecycle consideration of primary energy consumption, green gas emission, resource depletion, and waste management of modular homes is better than conventional homes. According to research, modular homes consumes up to 5% less lifecycle energy and emits 3% less green house gas than conventional homes.
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