thread, in the field: the rite joists

Wood or Steel? For us it was an obvious choice to go with steel. A condo building of our size by code requires that it be non-combustible, and with cast concrete floors (with radiant heat, ahhh) our floor framing needs to accommodate the weight. So what's so special about our joists? These are MarinoWare Joist Rites, very different from the typical light gauge metal joists. While they are a bit more expensive, they offer the ability to bear heavy loads, with a higher strength to weight ratio. They have large elegant openings that contribute less to thermal bridging as there are fewer conductive pathways, and provide avenues within the floor cavity to run mechanical, plumbing and electrical conduits. In addition, their recycled content is above industry standards, and they are manufactured in New Jersey, locally.

From a sustainability perspective, there are quite a few factors underpinning materials selection - embodied energy, recycled content, recyclability, place of manufacturing and harvesting, durability, lifespan, ease of installation, and ability to meet codes. Steel joists are straight, allowing for ease of leveling; do not warp, mold or rot; are light weight, allowing other structural members to be smaller; do not burn; allow for flexibility in design; prevent trees and their carbon sink from being removed; requireno chemical treatments; are easily recycled; and typically contain recycled content of around 25%.

BUT, steel joists have a higher embodied energy than most other options, with 35MJ/LB without recycled content, and between 8.9MJ/lb to 30MJ/LB depending on recycled content(1). This compared to wood at 10MJ/LB is a significant issue. What is embodied (or embedded) energy? It is an energy assessment of a product, taking into account the energy required to extract its raw materials, plus the energy for primary and secondary manufacturing, sometimes including transportation. A problem with these calculations, is that there is not a standard by which companies, or organizations follow, so we are often not comparing apples to apples. In addition, the embodied energy is not a life cycle calculation, which would account for the lifespan of the material, and what happens after the use. Once again, Lifecycle is also not standardized. The lifecycle of steel joists is better than that of wood because of its ease of recycling, and its longer lifespans.

A few stats about Joist Rite : Total Recycled Content: 32.7%, Post-Consumer Recycled Content: 25.5%, Pre-Consumer (Post Industrial) Recycled Content: 6.8%