The case for reclaimed materials sustainability is simpler than it sounds: every old fixture already spent its energy to exist. The energy to mine the ore, fire the kiln, mill the metal, and make the thing got spent decades or a century back, and none of it is refundable. That spent energy is what people mean by embodied carbon, and it sits under the whole case for reuse.
The math of reuse
The math is short. A new part, however clean the factory, starts from nothing: raw material, energy, transport, all fresh emissions, now. A reclaimed part has that bill already behind it. Reusing it adds only the small cost of recovering and restoring it, and against that sits everything that doesn't have to be made new. Keep an old fixture in service and you've skipped manufacturing its replacement entirely.
Old glass, old brass, and the marks of use are real reasons to choose reclaimed parts. There's a plainer reason too: reuse is among the lowest-impact ways to finish a building, because the footprint is behind the object rather than ahead of it. Recycling breaks a thing down and remakes it, spending energy again. Reuse skips that step and keeps the object whole.
There's a limit worth stating. Reuse only counts when the part goes back to work, doing the job a new one would otherwise do. A salvaged fixture admired on a shelf and never installed saves nothing; the saving happens only when it replaces something you'd otherwise have bought new. The saving lives in use, not ownership.
Salvager's Note: The saving is real only when the part goes back into service. On a shelf, a salvaged fixture saves nothing; installed in place of a new purchase, it avoids the whole cost of making that new one.