Most of the country has attic temperature problems in summer. Arlington TX has an extreme version of that problem. The combination of intense direct sun, high ambient temperatures, and the dark roofing materials common in DFW construction creates attic temperatures that are literally twice the outdoor temperature on a 95-degree day.
That heat has three effects: it increases the heat load on your living space and makes the AC run more, it degrades roof shingles from the underside faster than normal, and it shortens the life of any equipment stored or run in the attic — including HVAC equipment and ductwork.
An attic fan running on a thermostat cuts peak attic temperatures significantly by exchanging that superheated air with cooler outside air. Most Arlington TX homeowners who install attic fans notice a reduction in AC runtime within the first summer.