During the summertime, the humidity levels in my house run between 48 to 54% with 50% being the average. The HVAC company which installed my AC unit says these humidity levels are too high and recommended that I install a whole house dehumidifier.

What would be an optimal humidity level in my home during the summer? Wouldn't a thermostat with a humidity/dehumidity control on it do the job for a lot less money? I live in central Massachusetts. My house is 2100 sq. ft. and I have a 3.5 ton AC unit/coil on my furnace (with floor registers). Thanks!