Fiberglass remains the reigning champion of residential ROI in Texas. It is highly affordable, non-combustible, and violently effective when applied correctly. However, a "fiberglass job" encompasses radically different scopes of work depending on the contractor's ethics.
The Three Tiers of Intervention
Simply blowing 6 to 8 inches of new white fiberglass directly over the existing old insulation to cross the R-38 line. The cheapest option, but it traps old dust and completely ignores critical air-sealing physics beneath the floor.
Full clinical vacuum extraction of all old material down to the bare drywall. Spray-foam air-sealing of all wire penetrations, can lights, and top plates. Then, blowing a pristine 14-inch blanket of formaldehyde-free fiberglass.
Tier 2 extraction and sealing, followed by R-49 deep-blow fiberglass, perfectly constructed attic dams, insulated hatch tents, and a fully stapled silver Radiant Barrier applied to the roof rafters above.