Choosing carpet for green-built homes is similar to any other category: You start with the macro-attributes—in this case backings, fibers, cushion, adhesives, and stain treatments—and then break these elements down to evaluate their raw materials, chemical makeup, durability, and end-of-life characteristics.

Adding to these challenges is the fact that carpet isn’t a category home buyers or owners often have on their green radar. So you’ll either need to properly communicate the benefits of sustainable and healthy choices—and why they’re important—or offer these products as standard practice. Here’s what to look for.

Basic Makeup

The anatomy of carpet is fairly similar across the board: fibers in a primary backing, which is bonded with adhesives to a secondary backing. Most are dyed, some include topical stain treatments, and the majority are installed over a pad or cushion.

What this means is there are a lot of ingredients to keep track of and a lot of questions to ask about raw materials, recycled content, chemical makeup, and end of life for each element.

The most common fibers are nylon 6 and nylon 6,6. Among other synthetics are polyester and polypropylene (olefin). Because these materials are petroleum-based, manufacturers are working to incorporate recycled or bio-based content.

For example, Mohawk’s “SmartStrand” uses 37% corn-sugar content. Global sustainability director Jenny Cross says the material is engineered to be inherently stain resistant, eliminating the need for topical treatments.

PET (polyester) fibers often incorporate post-consumer recycled plastic bottles.

Natural fibers are an alternative to oil-based synthetics, with the most common being wool from New Zealand, Australia, and the U.K. This means there are transport considerations, and wool also carries a price premium. Wool makers argue that the natural ingredients and a long life span (high-quality wools can last 20–25 years, says James Stinnett of Earth Weave) make up for these trade-offs. Wool carpet is naturally stain resistant; some still contain dyes, and be aware that some might add chemical moth preventatives.

“Hard fiber” naturals are made from sisal, reeds, or grasses—and, like wool, are readily renewable but also transported long distances. The products are coarser, so they’re often used for a neutral area rug over hardwood or other carpeting, says Marty Wessinger of Design Materials International. Prices vary, with some reed products matching low-end nylons while others hit premium price points, he notes. Stain resistance also varies by material.

Indoor Air Quality

The origin of the fibers, however, is often a secondary consideration among the green community, which tends to focus on occupant health stemming from off-gassing.