Prefabricated homes, or “prefabs”, are houses fabricated in a factory and shipped in segments to their final destination. They are adored by design magazines, environmental activists, and movie stars alike. Prefabs rose to fame as a quick, cheap way to build houses. Today, prefabs are lauded for their “sustainable” nature, especially in comparison to traditional, stick-built homes. But are prefab homes truly better for the environment?
The main difference between a prefab and a stick-built house is where they are produced. A stick-built home, or what we think of as a “conventional house,” is built on-site. A prefab home is built inside a factory and shipped to its site in individual “modules” or sections that are pieced together like a huge jigsaw upon arrival. Many of the arguments in favor of prefabs cite this off-site, factory-style building process.
One such argument is that prefabs produce less waste than stick-built homes. Most prefab homes are constructed following a specific formula for materials needed to complete the project, meaning that builders are less likely to order in excess. In the event that there are leftover materials, they can be stored in the factory and used for future projects. On the other hand, traditional houses are more subject to customization than prefabs, making it harder for them to follow a set method of design and increasing the likelihood that builders will order a surplus of materials. Though these extra items can be recycled, they are usually dumped in landfills due to a lack of recycling infrastructure and economic incentives. Additionally, because the materials used in stick-built houses are stored outside, they are more susceptible to weather events, vandalism, and theft than those used in prefabs. Any damage incurred must be replaced by new materials, producing more waste.
According to Elemental.Green, a website that provides information on green home building and design, prebuilt homes “require more material in their construction than non-prebuilt homes because they have to be reinforced for delivery to the site.” Because this reinforcement process is material-intensive, it results in an excess of materials when compared to the amount used in traditional building. However, the amount of additional materials depends on the efficiency of the builder. Still, although prefabs require more materials, they are not wasted or sent to landfills. These additional components also strengthen the exterior of the home.
While prefab homes may not differentiate themselves in design, Tobias Roberts, a writer for Rise, says that “because prefab homes are more efficient in the use of building materials, they can often afford to invest in higher quality resources and supplies” and that the “choice of better building materials depends on the individual contractor.” This means that homeowners interested in living in a healthier home can seek out contractors that are willing to use more environmentally friendly components like “low-VOC materials, bamboo plywood, and FSC-certified wood without significantly increasing the final price of the house.” Therefore, the main difference is in price. Prefab homes make the implementation of eco-friendly materials more accessible, but these materials can still be incorporated into stick-built homes.
Another argument for modular homes’ eco-friendliness is their smaller impact on building sites. Whereas traditional house-building projects take place on a site from start to finish, prefabs are transported to a site once they are prepared for installation. This diminishes the amount of time that disturbances like dust, surface runoff, soil erosion, vegetation degradation, and potentially harmful chemicals are present at the location. Due to the indoor, assembly-line nature of prefab fabrication, the projects often take less time than stick-built ones to complete. Donna Peak, an executive director of the National Association of Home Builders, claimed that “depending on the complexity of the [prefab], it can take three to four months to build and get it move-in ready,” while a stick-built house takes “about nine months to a year to construct,” further disrupting the site.
In short, prefabricated homes seem to be marginally better for the environment than stick-built homes, but certainly still have impacts. Prefabs outperform stick-built homes in reducing site disturbances and employ fewer resources in the long-run, but present issues of upfront material waste and efficiency. However, because modular homes are usually cheaper to build than traditional ones, these slight differences could add up to something more significant if prefabrication becomes a more popular building choice. According to Nathaniel Otto, a writer for Panel Built Inc., “modular construction takes advantage of the microeconomic term of economies of scale,” meaning that as more structures are produced, the variable cost per module decreases. The decreased costs could allow prefab contractors to invest in more eco-friendly materials and to market homes at a lower price, should they choose to do so. Furthermore, as the annual production rate of construction and demolition waste for the whole planet was around 3 billion tons in 2000 and has since increased, a large-scale shift to prefab manufacturing could considerably decrease the waste from the construction industry.
El-Haggar, S. M., PE, PhD. (2007, September 28). Sustainability of Construction and Demolition Waste Management. Retrieved November 06, 2020, from https://www.sciencedirect.com/science/article/pii/B9780123736239500101
Environmental.Green Editor (Ed.). (2020). Your Resource for Green Home Building & Design. Retrieved November 06, 2020, from https://elemental.green/
Gale, S. F. (2007, September 27). The Marriage of Prefab and Sustainability. Retrieved November 06, 2020, from https://www.greenbiz.com/article/marriage-prefab-and-sustainability
Green Home Gnome Editor (Ed.). (2020, April 19). 7 Benefits of Prebuilt Homes. Retrieved November 06, 2020, from https://elemental.green/7-benefits-of-prebuilt-homes/
Lerner, M. (2018, June 20). Prefab houses were once the ‘holy grail of design.’ So why aren’t there more of them? Retrieved November 06, 2020, from https://www.washingtonpost.com/lifestyle/magazine/prefab-houses-were-once-the-holy-grail-of-design-so-why-arent-there-more-of-them/2018/06/11/2af7f14a-1011-11e8-8ea1-c1d91fcec3fe_story.html
McIntire-Strasburg, J. (n.d.). Almost 90% Of Construction Waste Can Be Reused/Recycled. Retrieved November 06, 2020, from https://www.smartcitiesdive.com/ex/sustainablecitiescollective/almost-90-construction-waste-can-be-reusedrecycled/1165795/
Otto, N. (2020, April 19). How Modular Construction Works. Retrieved November 06, 2020, from https://elemental.green/how-modular-construction-works/
Roberts, T. (2020, June 18). Is Prefab Better Than Traditional Building? Retrieved November 06, 2020, from https://www.buildwithrise.com/stories/is-prefab-better-than-traditional-building
SCJ Alliance. (n.d.). LID ELEMENT #1: MINIMIZE SITE DISTURBANCE (1035088731 793005814 Olympia, Ed.). Retrieved November 06, 2020, from http://m.olympiawa.gov/~/media/Files/PublicWorks/Water-Resources/LID/Elements/LID-Element-1.pdf?la=en
Taylor, A. (2015, November 13). 5 Things You Must Know About Buying a Prefab Home. Retrieved November 06, 2020, from https://www.kiplinger.com/article/real-estate/t010-c000-s001-what-you-should-know-about-buying-a-prefab-home.html