Whether a backyard ‘green-thumber’, or a bottom-line conscientious commercial manager, owning and operating a properly functional greenhouse throughout the year depends on one’s ability to maintain temperature parameters specific to what you are growing.
In the winter, you must keep the temperature from falling below a certain level….typically achieved by providing some type of supplemental heating system.
The key to minimizing your capital outlay while maximizing the efficiency of the particular heating system depends on a variety of factors and influences such as site location, the glazing material used to cover your greenhouse and what particulate species of plants you are cultivating.
For example, if you live in the Northern tier of the US where minimum outside temperatures fall below zero degrees Fahrenheit….it would be wise to have at least a double layer insulating glazing material to substantially reduce heat loss.
Positioning the greenhouse such that it is not hit directly with the prevailing northern winds also aids in controlling heat loss.
To hold down on heating costs, plan to grow cooler loving crops, such as lettuces and specialty greens that can handle a 55 – 60 degree high inside temperature level….as opposed to 70-75 degrees needed for tomato, eggplant, and peppers crops.
If you are fortunate to have a gas well in the ‘back-40’….then you have little to be concerned about. But if you are like 99.9% of folks doing their do-diligence to make a wise choice…then plan to do a good amount of research in making this decision.
Sources of heat range from natural or LP (liquid propane) gas, fuel oil, wood logs/pellets, as well as various other natural biomass fuels all of which can be adapted to various heating systems. From conventional propeller driven convective systems, floor or tube-finned radiant heat, geothermal, solar, biomass electrical generation waste heat, to other innovative methods… all need to be considered.
Highly recommended are the use of HAF air-circulation fans in conjunction with the heating system which constantly keep the air stirred, preventing the heat from settling in the roof of the greenhouse, eliminates air-stagnation and high humidity levels which result in fruit rot and fungal growth problems.
Conversely, in the Summer or in sub-tropical climates where high levels of heat is the norm…the challenge is to maintain temperatures in the greenhouse below tolerable levels that allows the plants to grow and thrive without excessive heat build up and associated plant stresses.
In commercial applications where a single span greenhouse or where 2 or 3 bays are gutter-connected, an effective basic design of the greenhouse can incorporate fixed or movable ridge vents or curtain systems in the roof. These passive systems allows the super-heated hot air to escape naturally, while fresh cooler ground level air is drawn into the greenhouse through sidewall curtain systems. These can be manual or automated.
When covering much larger areas under one roof for serious commercial production, then the use of mechanical exhaust fans, fresh-air motorized intake shutters or vent windows….and ultimately evaporative cooling or atomized fog-cooling systems must be incorporated if in an excessively hot, dry climate. In some instances, refrigeration units are tied in with an in-slab series of tubes that circulate chilled water through out the entire floor area of the greenhouse.
No matter what level of technology is used, it requires proper evaluation and planning of the project location, greenhouse design and covering, and the particular crops to be produced to ensure a successful greenhouse effort.
Whether you’re planning your first greenhouse….or are a seasoned grower expanding your greenhouse range, we’ll be happy to assist in the development of your project.
Let us hear from you today.