If your house was built in the 1980s or 90s, the attic is almost certainly lined with long strips of pink fiberglass batting. Homeowners assume because it hasn't caught fire, it is still working. The microscopic truth is that 30 years of Dallas humidity has mathematically destroyed it.
Lofted Air Pockets
Fiberglass does not actually insulate. The microscopic air pockets trapped between the glass fibers are what inhibit thermal transfer. When batting is new, it is highly lofted, trapping millions of tiny air pockets.
The Moisture Crush
Over 30 cycles of humid spring rains and 100°F baked summers, the extreme moisture gradients cause the thin glass fibers to break down and physically adhere to each other. The weight of the microscopic moisture collapses the "loft." The batting shrinks from 6 inches down to 3 inches. The insulating air pockets are crushed out of existence.
That old pink batting is no longer acting as insulation; it is now simply a heavy, dirty blanket lying on your ceiling drywall. It must be vacuumed out.