Ok, lets start what we mean by environmental control and what is it. Environmental control is what temperature, humidity, air quality. Lets take theses one at a time so I don't loose you.
Temperature: This is the current temperature of you room or house. This can also be adjusted. Heating system can be Forced Air, Hot Water and Radiators, In Floor Radiant System (ether, electric or water). While air conditioning is normally forest air cooled by Freon, cold or chilled water systems can be used as well.
Humidity: This is the current humidity of you room or house. The humidity is controlled by two units.
Dehumidifier, a device which is basically a small air conditioner.
Humidifier, a device which inserts water vapor into a forced air duct.
Air Quality: This is comprised of several items.
x per hr
How many times the air in the house is turned over every hour. Air Changes / per hour = ( 300 CFM x 60 ) / ( 15'x20'x8' ) or about 7.5/per hr.
Air filter performance. This is accomplished by a mass-flow sensor which can be found in most cars. as the dirtier the filter the less airflow you will have.
How much fresh air are you letting in the house by a Air-to Air Heat Exchanger. This is a must have in a tight house.