Modular Prefab: What a Homeowner Should Know

July 2, 2018 | Tom Bassett-Dilley

There’s a terrific video my buddy Corbett did for the Illinois Association of Energy Raters called “If Cars Were Built Like Houses.” It challenges homebuyers to think about what level of performance they will get out of the huge investment they’re about to make. What if houses were built like cars—in a factory, with quality control and third-party testing? That’s how we approach modular prefab—a way to get a better, more predictable product. The first thing to know is that a modular prefab house can be a “trailer home” or it can be a high-design high-performance, low-toxicity (no “new car smell”) home.

The idea of factory-building homes instead of site-building them has recurred with every generation of architects since the early 20th century, and the arguments for it remain pretty consistent:

  • It’s better to build in the controlled environment of a factory instead of a wet, windy, cold, muddy field;
  • Quality control tends to be more consistent in a manufacturing setting than a field setting;
  • Cost control is more reliable in a factory due to bulk purchasing, consistently trained labor, predictable work flow and methods, and the parameters of module sizes;
  • It can be way faster than site-building: the foundation can go in while the modules are being built, and the modules can get set in a day, taking months out of the overall build time;

Hi Tech Housing workers inspect one of the six modules of the Modular Prefab Modern Farmhouse.

  • There can be a lot less waste, and/or better control of waste, in the factory.

As we have worked our way deeper into the world of health-promoting, highly energy efficient, high-design homes, we have found another interesting advantage: by establishing a “kit of parts” with the prefabber, we can have predictable cost and performance together, something we find less predictable than with our one-off, site-built projects.

Our goal is to make beautiful, healthy, near-zero-energy homes accessible to the broadest market possible. The more we look to keep costs down, the more we have to eliminate surprises and the on-site learning curve. Most of the challenging connections (window flashings, air sealing, etc.) and material specifications (non-toxic adhesives, caulks, paints, etc.) are part of the protocol we’ve established with the factory; the site work—foundation, utilities, siding, roofing, and solar PV—are well understood and relatively easy to contract in any locality.

On the flip side, there are some things to be aware of:

  • Modules need to fit on trucks and get hauled over the highway, so there are size constraints; and some designs can require unusual module sizes or configurations to pull of something other than a boxy design! But as we learned in design school, constraints are good—we work with them creatively.
  • There is a cost to hauling the modules, renting the crane, and hiring the “set crewto assemble the modules on set day. Here in Chicagoland cranes are expensive—at least that’s what we’ve found so far. Still, these costs don’t outweigh the speed, quality, and cost benefits of modular.
  • Here in Illinois, some municipalities are hesitant to embrace modular homes. From requiring Illinois licensed trades (which the Indiana factory doesn’t have typically on staff) to allowing third-party inspections, there can be some issues to resolve with the municipality before committing to the details (and sometimes the possibility) of modular construction and delivery.
  • Some modular prefab companies have their own kit of parts and assembly preferences, and some just do their stock plans.

It’s good to keep in mind that the detached single-family home is inherently more expensive and more energy intensive than multi-family housing. But many of us here in the US desire and expect them; and we have neighborhoods full of inefficient homes with 19th-century layouts that need complete overhauls and sometimes full replacement. For new infill, modular prefab can make the most sense.

I don’t believe modular prefab is a magic bullet or huge disruptor about to change the face of home building; but it can be a great way to streamline a high-performance home solution. As on all our projects, we’re seeking to provide the greatest connection to nature, an invigorating and healthy place to live, extreme energy efficiency, and economy; we believe modular prefab can help us bring this more quickly to more people.

Tom Bassett-Dilley Architects | Contact