You can't call another sketch. Only one sketch can be uploaded at a time.
You can combine the functionality of one sketch with that of another sketch, if you know what the requirements for the resulting sketch are.
HighTemperature(); //Calls the HighTemperature function.
LowTemperature(); //Calls the LowTemperature function.
HighHumidity(); //Calls the HighHumidity function.
This crap really bugs me. The TemperatureControl() function should be what is determining of the temperature is too low or too high, or the humidity is too high, and should call the appropriate function to deal with the problem.
If it is too cold, calling HighTemperature() doesn't make sense.
Sending a text message every time the temperature is noted to be over 85 doesn't make sense. You want to send ONE message when the temperature becomes over 85 and ONE message when the temperature becomes less than 78 degrees.
What are you sending binary data on the serial port?
That first code is missing the implementation of a lot of functions.
Oh. They are all implemented in the other code. Why? They need to be implemented in the first code.