| While the basic intention of a greenhouse is to | | | | this may not be the best option. |
| conserve heat in an attempt to maintain a | | | | Another option includes the separated heaters. |
| constant temperature during those cooler hours, | | | | This form of heater used in heating greenhouses |
| many gardeners have found that the solar energy | | | | expels exhausted air from the heater through an |
| trapped during those warmer days is not | | | | exhaust system that runs through a wall or ceiling |
| sufficient to provide temperatures in the | | | | to the outside. The flame is concealed within the |
| necessary ranges to support plant life. This has | | | | heater making it a better choice for buildings that |
| led to searching for alternative options for heating | | | | may have contaminants in the air. This type of |
| greenhouses. | | | | ventilation can be gravity dependent or powered. |
| A variety of heating sources have been tried but | | | | Those that are gravity dependent rely on natural |
| those that remain the most popular include electric | | | | air drafts to expel exhaust. Fresh air must then |
| and combustion type heaters. This article | | | | replace this exhausted air. Powered options use |
| discusses the different types of combustion | | | | smaller pipes that can run vertically or horizontally |
| heaters available today. | | | | because the exhaust is pushed out, however, it |
| Combustion heaters are offered based on their | | | | still requires fresh air replacement. |
| type. The classifications include open, separated | | | | The third class is the sealed combustion heater. |
| and sealed. These heaters are great for heating | | | | Using a direct vent for intake and exhaust, this |
| greenhouses; however, each one is intended for | | | | form is similar to the separated classification in the |
| specific situations. | | | | fact that it uses outside air and the burner is |
| The open combustion heater utilizes the air within | | | | completely enclosed. |
| the greenhouse for combustion and is a good | | | | Heating greenhouses with this sealed system is |
| choice in areas that are free of air contaminants; | | | | unique due to its ability to exhaust air and at the |
| however, flammable liquids must be kept away | | | | same time pull in the necessary fresh air. The pipe |
| from the open flame of this type of heater. | | | | construction consists of one smaller pipe placed |
| Because these heaters are not vented to the | | | | inside a larger one. As the exhaust leaves through |
| outside all gases produced are contained within the | | | | one pipe it causes the intake of fresh air through |
| greenhouse itself. While these are useful on a | | | | the other eliminating the need for additional fresh |
| short term basis, if one is housing sensitive plants, | | | | air replacement like the separated heaters. |