Especially in these times of high energy costs, heating or cooling your greenhouse will probably be the most troublesome aspect of running your greenhouse. Sundance Supply has a helpful formula for calculating the size of the heater you will need based on the size of the greenhouse and the difference between your coldest outdoor temperature and the warmest indoor temperature that you will need to maintain.
The major choices for home greenhouse owners are electric or gas heaters. Gas heaters must be properly ventilated to allow for the removal of exhaust gases to the outside of the greenhouse. The by-products of combustion from a gas heater can be deadly to sensitive plants such as orchids unless there is proper venting. Electric heating units has two large drawbacks. Namely, the high cost and the problem of unexpected outages. One night with the power out can kill a collection in a hurry if you don´t have a backup plan.
In his book, Greenhouse Gardener´s Companion, author Shane Smith advocates solar heating of greenhouses using insulated walls, more layers of glazing and thermal storage using drums of water. These principles can help any greenhouse owner cut heating costs.
Cooling a greenhouse can sometimes be more difficult that heating. The first step in improving ventilation is to be sure that the greenhouse that you choose has properly placed vents allow for good air circulation. Most greenhouse suppliers have available electric or solar-powered vent openers so that you don´t have to be at home every time the sun goes behind a cloud. A thermostat opens and closes the vents as needed.
Most grower´s will not be able to get by with just using the available vents to cool a greenhouse. That means that a cooling fan is next on your shopping list. Careful planning is needed to ensure that you are getting efficient air movement. Another popular type of system in dry climates are misting systems that spray a fine mist or fog on the plants to keep them cool.
Shading the greenhouse during the hottest part of the day is another way to keep it cool. Special compounds are available for painting on the glazing to cut the sun´s rays. Be sure to check with the manufacturer for the proper material to use on your particular glazing material. Shade cloth is also available in a variety of colors and densities and can be temporary or permanently attached to the framework of the greenhouse.
Obviously, each homeowner´s situation is different and each person will have plenty to consider when deciding which kind of heating and cooling equipment to use. Whether you plan to build from a kit or have a custom greenhouse designed, your greenhouse supplier will be an excellent source of advice and recommendations for greenhouses in your region.
Charley´s Greenhouse carries a full line of greenhouses and supplies. Check the link below for an idea of some of the items that are available.
