Negative Pressure & Natural Ventilation

Fan & Pad Negative Pressure Cooling

The most traditional design on the market and by far the lowest cost method to cool your greenhouse. Negative Pressure cooling uses exhaust fans at one end of the greenhouse to pull or exchange the air in the greenhouse out of the building with fresh outside ambient air temperature at least once per minute. The temperature can be lowered through evaporation of a simple pad system or cool cell. As the air is chilled through evaporation, it is pulled to the opposite end of the greenhouse and forced out of the building through the exhaust fans. This cycle happens over and over again up to 1.3 times per minute. While this is the most inexpensive capital expense as well as most economical operational expense, this is the least effective method for hot humid climates to produce cannabis. In fact, without switching completely to an extraction only operation during hot humid months in certain parts of the country, this method of growing may be unusable.


Natural Ventilation with sidewalls and roof vents

Natural ventilation operates on the principle that heat is removed from the greenhouse by wind and temperature differences between the inside and outside of the greenhouse. Wind is what we primarily depend on. Even light winds as low as 1-2 mph are sufficient to keep the inside temperature of the greenhouse within a few degrees of the outdoor
temperature. When ridge vents are used, the hot air inside the greenhouse will rise and escape through the roof opening. The greater the difference in temperature between the inside and the outside of the greenhouse, the greater the results.


What are the advantages of Natural Ventilation?

There are a lot of crops that do well in greenhouses with natural ventilation. The lower initial cost sidewall rollup curtains versus the high electrical cost of operating exhaust fans makes natural ventilation an attractive option. Greenhouse sidewall vents provide a low cost, low maintenance solution.