From leveraging prefabrication to increasing modular construction, there are many ways to complete facilities faster while improving cost and predictability.
For prefabrication to have a significant impact on schedule and cost, it must be part of the design. The historical way of doing prefab was to start from a design based on a stick-built concept and search for parts and pieces that could be built off-site, thus modifying the design after bid and sometimes even during construction. These modifications could include layout, room size, and orientation, which are not easy to do at that point in the project. Including prefabrication as part of the design means engaging designers of record, vendors, and contractors early on to work through logistics such as:
- How much equipment can be fit into a prefabricated package?
- How big is it and what are the shipping limitations?
- Once delivered, is it feasible for trade partner installation?
- Is it scalable, or repeatable?
- In a perfect world, prefabricating as much of the building as possible is ideal. But these types of questions must be answered during design.
Designing for Modular Construction
Starting with modular block concepts and building the design around it allows for efficiencies from standardization in design, the prefab/modular construction, and the on-site work. An example of this is a modular UPS container or open skid. The input switchboard, output switchboard, UPS modules, and even battery cabinets can be mounted in the containers or open skids, and all the wiring between can be terminated and tested. The designer can now lay out the room and create the path into the room for install and the electrical/mechanical design according to exact equipment.
Designing with prefab in mind leads to a more streamlined modular construction process. With an emphasis on speed to market, modular construction allows for container or open skid integrators to build the modules off-site at the same time as the contractor is building the data center structure. “Typically, the contractor builds the shell [building] before sending the equipment to the facility,” said Graham Jones, senior project manager, JE Dunn Construction. “Once at the facility, trade partners then install the equipment and the mechanical and electrical connections. Rather than scheduling from start to finish, modular construction allows you to sequence the shell build and fabrication start to start.”
Using a traditional field assembly, also referred to as stick-build approach, the major mechanical, electrical, and plumbing (MEP) equipment cannot arrive to the site until the building is dried in, the roof is on, and equipment rooms are ready, which is generally three-quarters into the project schedule (this timing depends on location, design, scale, etc.). The modular approach enables fabrication and integration to work in parallel with the shell build.
Modular containers and open skids contain all assembled equipment and are shipped directly to the site for installation of each component as trade partners are ready for them. This cuts the time in the schedule they would typically use to connect the parts on-site for a stick-built project.
“Skids increase speed to market for our trade partners because everything arrives ready to install; they just rough-in upstream and downstream,” said Jones. “With a stick-built facility, manufacturers ship everything separately, so you would have multiple orders and ship dates to sift through on-site. Skids eliminate this since the manufacturer puts everything together at their location, and this simplifies on-site delivery and installation.”
Another benefit of modular construction as it relates to speed to market is the ability to deploy premade modules.
“If the client orders premade skids and has them on-site, that only makes construction faster and reduces the overall schedule,” said Jones. “One of the biggest risks to a data center schedule is getting the equipment on-site when you need it. Having premade skids available eliminates that risk.”
With modules assembled upon delivery in an open skid, less time is required for oversight during construction. Reducing the amount of time trade partners need to connect everything also trickles down to time on-site for the general contractor, meaning more money in owners’ pockets.
“When you eliminate labor required for any partner, the general contractor included, it also reduces costs associated with having those parties on-site,” said Jones.
Other Factors to Consider
While ease of on-site installation and schedule reductions are attractive with modular construction, owners must consider other factors when determining which solution is best for them. The first — and often biggest — factor to weigh is the cost now carried by the owner.
“To implement modular construction, owners typically carry the cost of purchasing the modules,” Jones said. “This can seem attractive to an owner at first because it reduces the contractor’s markup and overhead costs for the project. However, the owner is now responsible for making sure the vendor is providing the requirements of the design and any schedule risks involved with the equipment or skids.”
A solution to one of these problems has been hiring the contractor to manage the equipment even though the equipment is purchased by the owner — though the owner will still assume the schedule risk. While upfront costs can be higher for modular construction, they are offset by reduction of labor and overall duration onsite. Additionally, assembly in a controlled shop environment versus a construction site is safer, more efficient, and often produces better quality product.
Because modules arrive assembled, using modular construction also means an emphasis on communication between the general contractor and manufacturers. From a coordination standpoint, scopes must be established up front to be sure all parties understand where the general contractor’s scope picks up and where the manufacturer’s ends.
“These boundaries should all be delineated in the design documents,” Jones said. “This is why designers, vendors, and contractors should be involved early in the decision-making processes.”
Once clients decide on modular construction, they still have a couple options when it comes to installation: open skid or container. While similar in concept, both have distinct advantages and disadvantages when compared to stick-built construction.
Advantages and Disadvantages of Modular Construction Options
Delivering ready-to-install modules to the site eases on-site labor and reduces the overall schedule, but between the two modular options, there are different advantages and disadvantages. The obvious advantage of a containerized solution is the speed of install and the reduced building structure and footprint. The containerized modules are easily set in place on a pad outside the building — much easier than trying to fly an open skid into the building and skate it into place.
The open skid variable to consider is the structure itself. To account for sliding the modules into the building for installation, construction teams must leave openings in the side of the building.
“The building structure must be sufficient to handle the open skids, which is a cost and time component,” Jones said. “Teams must leave room for the skids and stagger installation based on construction, so it can affect how you phase the project.”
On the other hand, with the container, you do not need to have building space for the equipment. There is a reduced schedule and cost component to this smaller building footprint. However, this reduced building footprint and ease of install must be able to offset the higher cost of the containerized modules. The containerized modules have been known to be pricy due to the multiple shipping costs, as well as the limited supply chain for the market. While more companies are looking into containerized solutions, there are still only a few that can support this effort today.
Stick-Built or Modular?
So, which method is best? That depends on each owner and what makes the most sense for their needs and goals. While, today, the supply chain may be limiting when moving to modular construction, the benefits of a reduced risk to schedule, speed to market, reduced costs, and better standardization are very appealing to data center owners. Sometimes it’s hard to take that first leap into something different, but more owners are doing just that.
Article originally appeared in MIssion Critical magazine on Sept. 10, 2020.