Engineered lumber products are a green option for larger framing pieces, such as beams and columns, because they require fewer large trees to produce, and permit the use of misshapen trees. They also tend to be stronger and less inclined to warp than traditional lumber.
For instance, laminated veneer lumber (LVL) is made by gluing thin layers of fast-growth wood together; the large layered chunks are then sawed into dimensional lumber pieces. LVLs can be used as studs, headers, joists, beams, and roof rafters. Engineered I-beams, which combine plywood with flanges made of LVL or solid wood, can be used as floor joists or roof rafters.
The challenge with engineered lumber is the adhesive. The traditional adhesive contains formaldehyde. It can be hard to find greener forms of glue. But look for soy-based adhesives to avoid the offgas effects of formaldehyde.