I’ve tried the DHT11 sensor modules at both Vcc 3.3V and 5.0V, and at both voltages the humidity values are bad. dfrobot has introduced a V2 DHT11 sensor module that changes the 10K pull-up to 4.7K.

Sensirion SHT1x/SHT7x precision humidity and temperature sensor (Octopart search, starting at $25). This isn’t a cheap sensor. Octopart lists a few places to buy it .

For more information about the R155 temperature-humidity sensor or any of RF Code’s wire-free environmental monitoring solutions, call 877.463.0756 or contact David Gould at dgould[at]rfcode.com ...