How Sustainable Is Modular Construction?

Waste, Emissions, Longevity, and More

Blue modular home surrounded by trees and a lawn

Pratt Homes Briar Ritz / Wikimedia Commons / CC BY-SA 4.0

Modular construction, a type of prefab, is leading the way in eco-conscious building practices by slashing the industry's waste problem and maximizing recycled materials.

A modular is a portable home or commercial building that is built at an off-site facility and transported to a more permanent plot for assembly. The product can be of higher quality because it's made in a controlled environment. For all its environmental advantages, the global modular market is thriving, expected to grow by an impressive 50% from 2021 to 2028.

Here, learn more about factory-made modular builds and their environmental impact—from the materials used to the emissions generated to their longevity compared with traditional site builds.

Modular vs. Manufactured Construction

A key difference between manufactured and modular homes is their building codes. Manufactured homes follow the U.S. Department of Housing and Urban Development (HUD) Code, while modular homes follow state, local, or regional building codes.

Manufactured homes are often placed on wheels and come in one or two pieces. In contrast, modular homes are often built on basements or crawlspaces, not on wheels, and come in two or more pieces. They can look different from manufactured homes, resembling "stick-built" construction.

History of Modular Construction

Though modular construction is still considered to be disruptive to the industry today, the concept is thousands of years old. A period of expansion took place following World War II, when prefab trailers were set up to provide fast, low-cost housing. These trailers were officially rebranded later on as "modular housing."

Modular construction looks a little different today: Portions of the structure are built separately—from bottom to top—in a factory setting, wrapped with a weather-resistant membrane where they are open, then transported to the property by truck, and, finally, connected.

A certain kind of prefab called volumetric is even more simplistic. Entire six-sided structures with finished interiors are built in the factory and then merely bolted together at the building site.

Modulars have experienced a few popularity surges over the past century, from the quick-build trends of the '70s to the design boom of the early aughts to now, fueled by a modern-day housing crisis.

How Common Are Modulars Today?

A report by Dodge Data and Analytics said modular construction made up only 4% of the U.S. housing market in 2020. Other data shows that off-site projects account for a slightly higher and ever-growing portion of North American commercial builds—5.52% in 2021. Still, these numbers are minuscule compared to the modular market share in countries like Sweden (45%) and Japan (15%).

It's no coincidence that two countries known for their forward-thinking, green-minded architecture are also leading the charge on modular construction. This building style is believed by many pros to be the most sustainable.

Modular Construction Means Less Waste

Modular home being built in a factory

digitalhallway / Getty Images

One of the biggest draws of modular construction is that it's far less wasteful than on-site construction. When the European Union surveyed construction and demolition waste in 2008, it found that C&D materials, as they're often called, accounted for an astounding third of all waste generated in the region. In the U.S., C&D waste is twice the amount of municipal solid waste.

The controlled manufacturing environment of modular construction makes it easier to be precise in material usage. Any materials that aren't used for one project can be stowed away for the next without even leaving the facility. Factory building also eliminates waste associated with weather damage (inevitable when building on-site), therefore reducing the need for demolition and keeping materials nice enough to recycle at the end of their lives.

What's more, because modular buildings are virtually portable, they can be easily moved off a site to deconstruct and discard materials responsibly or to continue being used on another site—no need for demolition.

Overall, this method has been shown to reduce the weight of C&D waste by up to 83.2%.

Emissions From Modulars vs. Traditional Site Builds

View of modules being transported on large trucks form behind

Zigmunds Dizgalvis / Getty Images

Another big environmental advantage of modular construction is the reduction in emissions from frequent site deliveries. In fact, a 2021 study of new builds in Pakistan found that modular construction generated almost half the greenhouse gas emissions of conventional site-built building (about 3,450 kgCO2-equivalent versus 6,500).

Site deliveries make up a colossal portion of emissions generated from construction, but one must also consider the embodied carbon of building materials. When a building is constructed outside, weatherproof materials like concrete and steel are often used in place of wood because wood is prone to water damage (from rain or just general humidity). Research shows that using sustainable timber instead of manmade materials can reduce construction-phase emissions by 69%.

Drawbacks of Modular Construction

In the early days of modular construction as we now know it, this style might have had its limitations with regards to building size, style, and shape (the original modular designs were very modern and primarily rectangular). This would have restricted the creativity and uniqueness of the design, plus it would have meant finding a plot to suit the standard rectangular shapes.

Nowadays, almost any style of home can be made modular. Clayton Homes, one of the largest modular home builders in the U.S., makes very conventional-looking houses nobody would look at and say, "That's modular." Because the modules are constructed in a factory, there are still some limitations with regard to room sizes, ceiling heights, and the like.

Moreover, the transport of the modular home is expensive. Building sites should be close to the manufacturer in order to minimize costs and hassle. (Still, even with the manufacturer close by, back orders can occur and delay delivery.)

Another problem with this technique is that it can lack flexibility—meaning one can't usually make changes to the design once it's been finalized and the building starts. With a site build, designs can be updated during construction.

Frequently Asked Questions
  • What do modular homes look like?

    In the early days of modular construction, the homes were basic and boxy, leaving little room for creativity. Now, almost any style of home can follow a modular construction method.

  • What's the difference between modular and prefab?

    Modular is a type of prefab construction in which a home is built in self-contained building blocks, then assembled on the home site. Modular is widely considered to be the sturdiest type of prefab. At least 70% of the home is built off-site.

  • What factors make modular construction more sustainable?

    Because modulars are made in a controlled setting, they don't get damaged from moisture or extreme weather during the construction process, therefore reducing the need for demolition to rebuild. The materials that would normally be thrown out are also easier to recycle—they can either be kept at the factory and used for future projects or simply thrown into a bin that most traditional construction sites simply wouldn't have.

  • How long does it take to build a modular?

    The timeline can vary widely depending on the size and complexity of a build, but the consensus is that a modular home takes six to 18 weeks to build, transport, and set up. That's not including the time it takes to design the home (up to 12 weeks) and secure permits (up to nine weeks).

  • What's the life expectancy of a modular home?

    Modular homes are known to be incredibly sturdy because they're made in a factory setting with high-quality control measures and because they aren't weakened by weather during the construction process. While there's no official life expectancy, many manufacturers claim they last decades—50 to 100 years or even longer.

View Article Sources
  1. "Modular Market Construction Size, Share & Covid-19 Impact Analysis, by Type (Permanent Modular Construction, and Relocatable Modular Construction, by Application (Commercial, Healthcare, Education & Institutional, Hospitality & Others), and Regional Forecast, 2021-2028." Fortune Business Insights. 2021.

  2. "Prefabrication and Modular Construction 2020." Dodge Data & Analytics. 2020.

  3. "Permanent Modular Construction Report." Modular Building Institute. 2021.

  4. Manley, Karen, and Kristian Widén. "Prefabricated housing firms in Japan and Sweden: Learning from leading countries." Offsite Production and Manufacturing for Innovative Construction: People, Process and Technology. 2019.

  5. "Construction and demolition waste." European Union. 2008.

  6. "Sustainable Management of Construction and Demolition Materials." United States Environmental Protection Agency.

  7. Loizou, Loizos, Khlaegh Barati, Xuesong Shen, and Binghao Li. "Quantifying Advantages of Modular Construction: Waste Generation." Buildings. 2021.

  8. Pervez, Hamza, Yousaf Ali, and Antonella Petrillo. "A quantitative assessment of greenhouse gas (GHG) emissions from conventional and modular construction: A case of developing country." Journal of Cleaner Protection. 2021.

  9. Himes, Austin, and Gwen Busby. "Wood buildings as a climate solution." Developments in the Built Environment. 2020.