• A weather station with reliable and accurate outdoor air temperature information.  Wind speed and light information are optional, but can be integrated into the program if available.
• A hot water mixing valve providing hot water to the zone and a hot water temperature probe to tell the program how hot the water entering the zone is at all times.

This program will use the design of the greenhouse and heating system, along with the outdoor ambient conditions to accurately estimate and anticipate the zone's heat load.  The program is also self-tuning so it can adjust to real-world problems within the greenhouse (such as a torn heat curtain or stuck vent).