I have an American Standard TWE049E13CB air handler with a variable speed blower. The manual has a chart to adjust the dip switches for fan speeds for cooling, heating, fan off delay, and auxilary heat. I don't see anything to adjust the speed when the thermostat is set to fan always on.
In my two story home, even with additional attic insulation, it gets stuffy in the middle of the night. I estimate the fan runs at 30%-50% full speed when it is not cooling. Is there a way too increase the fan speed when the system is only circulating air and not cooling.