The thermal performance of off-site prefabricated buildings and building enclosure systems
By Val Sylaj and Brian J Hall
As designers and owners are becoming more aware of the environmental impacts of the construction industry, including the types of materials used, more stringent requirements are being imposed by specifiers, and national codes and standards.
This article provides some insights on the important measures of prefabrication and panelized systems on the thermal performance of buildings, the energy consumption, and the financial impacts to the investors.
A recent report from Dodge Data and Analytics published in 2020 shows a significant interest by the construction industry in prefabrication and modular construction mainly because of the improved productivity, reduced timeline, and cost, better sustainability performance, etc.
An earlier report from Dodge Data and Analytics published in 2011 had also highlighted the following as the underlying drivers and benefits of prefabrication and modular construction: (1) Improved productivity and quality are key benefits in its usage, (2) Positive impacts on budget and schedule performance are widely experienced, and (3) Construction sites are ‘greener’ due to less waste being generated, and safer due to working with structure assemblies and modules produced offsite.
Although major advances have been made in both prefabrication and modular construction since the 2011 report, many of the above mentioned factors are still consistent with the findings of the latest report from 2020.
What is Prefabrication and Modular Construction?
With rapid population growth, the construction industry is always challenged to adapt its technologies based on the market demand such as the need for taller buildings, reduced onsite construction times, enhanced building performance, etc. Prefabrication and modular construction are certainly a solution to most, if not all, of these demands.
Prefabrication is a construction method that involves fabricating and assembling building components offsite. It can refer to both flat elements (often known as prefabricated panelized systems), or to modular volumetric units that typically include complete spaces of a building such as an apartment unit, hotel room, jail cell, etc. In either case, prefabrication construction also provides innovative solutions in buildings where the entire building envelope can be fabricated offsite using prefabricated building components.
In addition to the need for accelerated building construction technology and consistency in quality, prefabrication and modular construction are also being considered to address concerns with site-specific skilled labour shortages. With prefabrication that is completely performed at an offsite facility, plant workers can be trained to perform specific skilled trades such as electrical and plumbing that form part of the finished element or room.
Standard building construction practices require individual building components or materials to be delivered to a job site, stored and then placed or installed by labourers from multiple trades. This requires significant on-site space as well as time for setup and construction. Another very time-consuming on-site operation process is the exterior finish of the final building façade.
Conversely, off-site prefabricated components are delivered ‘just-in-time’ and installed by a smaller crew of skilled installers/erectors, directly from the truck onto the building, with the façade and architectural finishes already complete.
It is clear that prefabrication is an ideal construction technology with minimal site disturbance and less labour required compared to traditional construction. Another important factor is improved safety, mainly because the work is done at ground level at a prefabrication facility, instead of working at elevated heights which is common with traditional construction. Further, the safety measures such as physical distancing during a pandemic can be easily implemented with very minimal or no effect on production.
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