If you have spent any time around offsite, you have heard it. Volumetric modular is inefficient because you are shipping air. A truck carrying a finished module is mostly carrying empty space, while a truck full of wall panels is packed tight.
It is one of the most repeated points in the volumetric modular vs. panelized construction debate. On its face, it is true. It is also the wrong measurement.
What a volumetric module costs to ship
Shipping volumetric modules is not cheap or simple. The federal width limit on the National Network is 102 inches, and anything wider needs an overwidth permit. Most modules are wider than that, so they move as permitted loads with route planning and, depending on width and state rules, escorts and travel restrictions. That is a real cost and it belongs in the comparison.
Moving a permitted wide load is a lot less Smokey and the Bandit and a lot more paperwork, pilot cars and travel curfews.
What panelized components cost to connect
Here is what the shipping air argument leaves out. Every piece that ships separately becomes a connection on site. Each connection is site labor, a crane pick or a hand set, an inspection, time exposed to weather and one more place for a leak or a misalignment.
An example from my own planning work, not an industry statistic: a three story, 24 unit garden style apartment building can be delivered as roughly 30 volumetric modules. The same building delivered as panelized components could be as many as 400 pieces, plus a dozen or more truckloads of finishing materials, depending on how complete those components are when they leave the plant.
Panels have their own shipping tradeoffs. Walls shipped flat can fit substantially more per load than walls shipped upright, in my experience as much as 60% more. But windows and doors do not ride well flat, so panel providers are often forced to choose volume over completeness. Loads also have to be stacked in reverse order of installation, or the site slows down while crews dig for the next piece.
If you grew up on Tetris, you already understand panel logistics. The difference is that on a job site the pieces come off the truck in reverse order, and there is no restart button.
Factory level of completion is the real question
The better question is not how much air is on the truck. It is how complete the building is when it leaves the factory. I think about it as a factory level of completion, a defined scale running from bare framing, to sheathed and boarded, to MEP rough in, to insulated and weather sealed, to windows and doors installed, to finished. Each step up moves work from the field into the plant, where cost, quality and schedule are easier to control. Each step also changes what you ship and how you ship it.
Is volumetric always the better answer? No. Is panelized always cheaper? Also no. As I wrote in February about why offsite adoption is slow, buyers are looking for predictability. The right answer depends on the site, the distance, the building type, the local labor market and how much risk the owner wants to carry in the field. Compare total installed cost, total schedule and total risk to a finished building, not the freight bill.
Freight is a line item. Connections are a risk profile. Price the risk, not just the truck.