Despite the slowdown in the economy, there's one area that continues to boom, and that's non-residential construction and, specifically, manufacturing construction spending. The latter is up sharply in recent years, reaching $214 billion in 2023. I think the theme may have more room to run, and stocks like Comfort Systems USA (FIX 1.83%), Carrier (CARR 1.22%), and Germany's Siemens (SIEGY -0.84%) are poised to benefit.The non-residential and manufacturing construction boomFirst, a few words on the spending ...