Wabi 2 Opening Windows

An enthalpy calculator is disclosed having a humidity sensor for sensing relative humidity, connected to a multiplier and a temperature sensor, for sensing temperature, also connected to the multiplier wherein the output of the multiplier provides a signal which is representative of enthalpy. The multiplier may be a variable gain amplifier with the temperature sensor and humidity sensor connected to the input and in the feedback loop in either order such that either the temperature sensor or the humidity sensor changes the gain of the amplifier.