The Foundation with the Lowest Footprint: Earthbags
Last Updated: Feb 19, 2025It has been said that a home is only as good as its foundation. Think about much we rely on our home’s foundation: it must hold up the weight of the rest of the house, resist wind and soil pressure, withstand frost, keep out water, pests, and soil, be its own conditioned living space, and serve as the actual footprint—and here we mean from a design standpoint, not the ecological footprint—of the home.
Table of Contents
- What’s an Earthbag?
- Are there any in existence?
- Pros
- Cons
- Bottom line
Most homes’ foundations are made from concrete—either cast-in-place, precast, or concrete masonry units (CMUs). Insulated concrete forms (ICFs) are also becoming more prevalent. What’s the problem with concrete? According to BuildingGreen.com, concrete “contains extraordinary embodied fossil fuel energy and a primary contributor to global warming. Concrete has many advantages as foundation material but should be used as sparingly as possible.” That’s what we mean by “footprint” in the headline: the ecological footprint of a home increases when concrete is used. So, what are some alternatives?
What’s an Earthbag?
As part of our research into innovative products for homes, we found one exciting way of making the foundation for a building. It’s called an earthbag foundation. It’s made by filling long, skinny bags with dry soil or gravel, then tamping and stacking them. Next, two or more courses of bags are stacked with barbed wire in between to hold them together to make the desired height.
The bags are made of a polypropylene material in long tubes used for farm feed sacks. However, the polypropylene sacks need to be protected from sunlight, so they don’t degrade. This can be done by backfilling earth against them or extending the building’s siding down over them.
The gravel and earth are directly from your building site or a local quarry, so there are virtually no transportation costs—making this one of the most sustainable ways to build a solid foundation. Can just any earth be shoveled into the bags? According to Endeavour, an innovative learning, building, and living center, “a wide variety of material can be used in the bags, as long as it has an aggregate content capable of being tamped to a high degree of compaction.”
For this reason, the embodied energy and environmental footprint of an earthbag foundation are far lower than that of a concrete foundation.
Are there any in existence?
The earthbag method has been used for structures all around the world, and not just for houses. A great example is the Trillium Lakelands Teachers’ Union Office in Lindsay, Ontario, Canada. This beautiful 2,400 square foot office building was built with many sustainable features, including photovoltaics, straw bale walls, and an earthbag foundation.
And, you can use the earth wherever you are located. They used road-base gravel and a small amount of a lime/metakaolin binder to provide a mixture that tamps well and stays coherent after curing, even if the bag is damaged or removed. It is also possible to use aggregate and clay in the bags.
Pros
- Low embodied energy.
Already mentioned above, earthbag foundations are possibly the most environmentally benign material imaginable for a home’s foundation, other than no foundation at all. - Low cost.
In addition to low embodied energy, earthbag foundations are easy to install and can be constructed using unskilled labor. The material that goes into the sacks can be found on location, so other than the sacks, it is free. These factors can make them much less expensive than alternative foundation materials. - Versatility.
Earthbags can be structured to be curvy, dome-like, or whatever pleases the builder/designer on the day they are being constructed. - Durability.
Earthbags are fire and flood-resistant and will not rot or degrade. If the bags are protected, they can last indefinitely. - Natural materials.
While we bristle at the overuse of “natural,” this is indeed the definition of natural materials. There are no toxins, and if the home is deconstructed, the bags can be emptied, and the material returned to the earth with no degradation.
Melissa Rappaport Schifman
Melissa became the Twin Cities’ fifth LEED for Homes Accredited Professional (LEED AP) and completed the work necessary to get her own home LEED Gold Certified, the basis for her book, Building a Sustainable Home: Practical Green Design Choices for Your Health, Wealth, and Soul, (Skyhorse Publishing, August, 2018). With her corporate experience in finance, marketing, and business development, and an MBA and Master’s in Public Policy from the University of Chicago, Melissa has been providing sustainability advisory services to businesses, governmental agencies and non-profits, focusing on strategic and operational change that provide bottom-line financial returns. She has led the LEED certification of two million square feet of commercial buildings, written GRI-compliant Corporate Sustainability Reports, is a LEED Pro Reviewer and LEED mentor with the U.S. Green Building Council. She is the founder of Green Intention LLC where she writes about sustainable home living.
