Page 11 - MASHRAE 35th Anniversary

This article was published in ASHRAE Journal, November 2020. Copyright 2020 ASHRAE. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about ASHRAE Journal, www.ashrae.org.
that can become disorganized, inefficient chaos. The building blocks of today’s construction sites are designing to meet a code requirement or functionality within the space using the same methods and technologies from the last 100 years. When designing for the new world, designers must design with the intention to
collaborate with the contractor.
Intentional design is critical in off-site
fabrication. When a contractor needs to build things in assemblies, engineers must use new methods that are more productive and minimize on-site labor. This off-site fabrication strategy is more conducive to an efficient build cycle.
The key to a successful prefabrication project is to have all involved parties participate in the design phase before using an off-site construction model. This eliminates the need for rework.
Compared to traditional building strategies, off-site fabrication can run more efficiently because it is a coordinated effort, and the process has to be coordinated for these technologies to work. Inherently, there is a need for a higher level of quality control to prefabricate off- site and bring the assemblies on-site.
Off-site prefabrication mitigates risks and provides a higher quality product to the owner. It also reduces costs and schedule because different trades are able to work off-site on parts of the building more efficiently than fabricating those building systems on a construction site.
An advantage for off-site fabrication is the working crews are experienced and in the same manufacturing facilities that are roofed, clean environments. In addition, this gives the trades the advantage to build assemblies at chest level, not necessarily in the ceiling. Productivity of manufacturing at chest level and on the floor is substantially increased when compared to working 15 ft (4.6 m) in the air. And this method is safer. Because fewer tradespeople are available amid the current labor shortage, finding ways to be smart and efficient is imperative. Companies can see off- site fabrication as a cost savings and return on equity.
Improved quality is also inherent. Building off-site allows for work to be checked easier,
It is a paradigm shift to use these tools and find partners on the construction side that have the capability and desire to do it. Contractual arrangements such as design build or integrated project delivery try to contractually bring team members together with a common financial goal. While these practices are helpful, the true guiding principle needs to be team members from design and construction wanting the same outcome and driving toward the same success.
Collaborative design software takes inputs from a basic load calculation of a space and transforms it into an energy model based upon limited information other than building use. These same tools take into account the manufacturing assemblies that will build the system. For example, for sheet metal systems the ductwork in the model no longer represents just a spatial constraint, but rather the pressure class of the sheet metal, gauge and type of metal, seam construction and joining method.
These tools provide the knowledge for a manufacturing intent at the same time as the initial design. They have also allowed for the development of multi-trade assemblies in which mechanical, electrical, plumbing, fire protection and low-voltage cabling are all built in a single environment off-site and installed in hours, rather than in days with previous “silo” methods.
Even with the available tools, technologies and innovations available, all team members have to be on the same page to have success.
New Build vs. Renovation
While prefabrication tends to be more used in new construction projects, prefabrication can also apply to renovations and equipment replacements, but the constraints and requirements are specific to the project.
Designers can prefabricate systems for renovations, but sometimes the project calls for specific variations and versatility. For example, a mechanical room that needs a new piece of equipment might have a set of double doors, so the prefabricated assemblies have to fit through the doorway. This can be done using strategies such as removing precast panels.
Challenges
Engineers face several challenges with off- site fabrication. The first is maintaining the off- site, collaborative mentality. If the designer is not
minimizes productivity.
Tools
rework
and increases
labor