Interview by Mary Kate McGowan, Managing Editor


From owners to designers to constructors, off-site construction has evolved to deliver value to various stakeholders, and the strategy does necessitate changes, according to 2020–21 ASHRAE President Charles E. Gulledge III, P.E., HBDP, Fellow ASHRAE.

“Delivering off-site solutions, at any scale, requires embracing some key procedural and physical best practices,” he said. “Procedural perspective requires us to change our mindset on how we approach design and construction.”

Gulledge talked with ASHRAE Journal about the evolution of off-site construction and how to better adopt and improve these strategies.

1. Why is now a good time for the HVAC&R industry to adopt off-site construction strategies?

The holistic off-site narrative has evolved as a response to delivering value in the design, construction and operation of built solutions. Off-site construction can help various stakeholders differently:

  • Owners are in pursuit of experiences that deliver working solutions, have connected knowledge, exhibit cost/schedule certainty, eliminate change orders and avoid conflicting narratives.
  • Constructors are looking for ways to increase productivity, remove waste in delivering built solutions, eliminate rework, provide higher quality and minimize on-site overhead costs.
  • Engineers desire design intent to become reality when built—not disputed across decoupled contractual interests.
  • Commissioning/testing, adjusting and balancing (TAB) resources seek coordinated systems that do what they are supposed to do.
  • With the evolution of virtual precision, those engaged in the delivery of built solutions are recognizing that off-site strategies can deliver value for all stakeholders. When applied correctly, this equates to high quality, reduced overall project costs and improved schedules.

2. What are some realistic ways people can use off-site construction strategies?

With the assistance of digital precision, off-site strategies can be used across a myriad of solution elements such as:

  • Individual facility services: elements can be preassembled at the shop and delivered to the field. This can take the form of plumbing batteries, coil hookups, terminal units with duct in/out transitions, control panels and power panels. What is built in the shop will interface seamlessly to the requirements of the field.
  • Increasing scale: equipment can be fully configured for field drop in. Let’s describe how this applies to an air-handling unit, for example:

    • A base frame can be fabricated to accommodate all unit modules, support for services and height to facility drainage provisions.
    • Modules can be assembled with appropriate elements to support airflow, filtration, thermal and moisture performance provisions.
    • Piping systems can all be configured to hookup points.
    • Control devices can all be mounted in the air, hydronic and steam transport paths. All I/O wiring can be factory installed and integrity checked.
    • All power wiring for equipment, controls and service can be installed and integrity checked.
    • Duct and piping systems can all be pressure tested to demonstrate project leakage parameters.
    • Fully configured units can be operated to demonstrate proper performance of system features. All sequences of operation can be simulated on the shop floor.
  • Equipment can be scaled to provide more robust facility services skid packages. There are many paths available here:

    • Complete heat exchange packages can be configured that include heat exchangers, steam service, condensate recovery, hydronic pumping, air/expansion control, makeup provisions, control and power.
    • Mechanical pipe racks can be configured for centralized feed of all services.
    • Pipe racks can be further enhanced to accommodate trade collaboration with fire protection feeds, power conduits and cable trays, and ductwork.
  • The possibilities do not end at the equipment and skid options. Rooms and floor plates can all be delivered via off-site methodologies, such as:

    • Complete central energy plants can be configured in modules for shipping to the jobsite.
    • Central electrical rooms with backup power provisions are feasible.
    • Tier IV mission critical space can be arranged, with 2N reliability.
    • Cleanrooms can be constructed providing clean good manufacturing practice (cGMP), pressure-controlled environments.

    The true definition of “at-scale” can be realized when we see off-site strategies being applied to delivery of complete building solutions. Pause and reflect on that a minute. With the advent of digital precision, we can virtually design an entire building, fabricate the building off-site in modules, prepare the site to receive the modular solution, ship the modules to the site staged for just-in-time flow and assemble the modules in sequence to form a complete solution.

    Now, think back through this progression of possibilities. Digital precision allows us to fabricate higher quality solutions, leverage vertical supply chain management of equipment and materials, virtually collaborate on where facility services fit together, eliminate rework in the field, minimize on-site general conditions, remove waste and deliver better customer experiences. Finding and delivering value are possible.

    3. How should building professionals new to off-site construction start using these strategies?

    Whether one is an innovator or novice to the HVAC&R ecosystem, off-site strategies necessitate adoption of lean philosophy in the design, construction and operation of built solutions. Via a continuous improvement process, we can deliver higher quality solutions with cost/schedule certainty, increase stakeholder productivity, minimize human and material waste and improve our profit margins. Here is an example:

    • The journey begins with acceptance that we are unaware of how fragmented our industry is. Our conventional delivery models yield a broken context.
    • Awareness follows and reveals how poorly we work in isolation as an industry. Our productivity is poor. Our processes are rife with waste. Intent-to-build representations do not correlate necessarily to can-be-built outcomes. Command and control transactional models do not facilitate optimization of the whole. We lose so much time and money recreating knowledge, managing multiple touch points, trying to make sense of disconnected knowledge, seeking information that is disconnected and reworking solutions that don’t fit or are in the way.
    • Awareness leads to understanding the root cause issues associated with our broken context. Lean principles can now be used to identify the importance of reliability, reduce uncertainty, identify and eliminate waste, introduce flow, manage a network of commitments, define what value is for a client and make progress to optimize the whole.
    • Competency is realized when we act on our understanding of insight.
    • Mastery is obtained when we keep repeating this process (on the job and job-to-job) in a continuous learning cycle to improve our capacity to deliver value. Mastery of the off-site narrative is achieved when we become aware of our fragmented ways, understand how to alter our delivery models, realize how collaborative optimization can be structured and demonstrate that we can provide better experiences for clients that support unique conditions of satisfaction.

    The off-site journey takes us on a new path that many are unaccustomed to. Command and control, transactional and start-to-finish practices fade away. We evolve to relational, collaborative and lean processes. Off-site is one of the strategies available to us to demonstrate competency of the holistic lean narrative.

    4. What are your recommended off-site construction best practices?

    Delivering off-site solutions, at any scale, requires embracing some key procedural and physical best practices.

    Procedural perspective requires us to change our mindset on how we approach design and construction. Let’s break this down:

    • Digital precision begins with using smart objects to capture knowledge. Design must shift from geometry depiction to information aggregation. Connected knowledge is critical.
    • Functional precision is afforded when we evolve to working from one narrative. Off-site success is possible when we work with a singular 7D BIM model, not multiple variants used to communicate design intent across a field of decoupled contractual interests.
    • A mind-set shift is required to capitalize on the collaboration element. Knowing who becomes responsible for the design and execution of specific work results is critical. Consider the example of the facility services rack:

      • The rack is designed to work with the building structure for upper attachment, or floor support, of all projected services.
      • Mechanical pipes are applied to the rack to support transport path routing.
      • Critical air transport paths are added to the rack.
      • Provisions are made in the rack design to account for Division 21 and 22 piping services.
      • Further accommodations are made to capture centralized power conduit and cable tray layouts.
      • All these facility services are placed on the rack on the shop floor. The full rack is shipped to the project site and lifted into place in the field. Trade coordination in the field is minimized. Rework is eliminated. Flow is improved.

    Physical best practices are rather self-evident. Infrastructure is required to support decoupled off-site, or near-site, logistics. Here are some examples:

    • Floor space must be available to fabricate, assemble and test off-site solutions.
    • Production space must be able to support just-in-time flow of materials, equipment and progressive assemblies.
    • Vertical supply chain management must be exercised.
    • Knowledge from 7D BIM models must be connected to production fabrication of materials.
    • A transportation network must be available to support flow inside the production facility, transfer to the project site and installation at the project site.