If you need to install humidity monitors, the most obvious choice is to buy one of the more advanced data loggers, as they are much more useful than simple hygrometers. There is a wide selection of humidity monitors available and you will have to choose those that are suited for your needs. Many humidity monitors require a computer to view the humidity data that they collect. There are some stand alone modules, however, (ThermaViewer is one of the examples). Before you decide to buy your data .