7 Tools to Cool a Summer Greenhouse
Article by Jean Gallagher
Greenhouse thermometer
Methods of both cooling and ventilating become essential. Think of a closed automobile that has been sitting in the sun. The temperature quickly rises and becomes unbearable. Open the windows and the hot air quickly escapes, even on the hottest days. As the car moves, the additional airflow cools the interior even more quickly. The principal inside greenhouse structures is no different.
The 7 most important tools in your greenhouse cooling arsenal are:
- High and Low Vents
- Cooling Fans
- Misters
- Fog
- Evaporative coolers
- Air Conditioners
- Shade Cloth
Vents
One of the most efficient ways to correct overheating in a greenhouse is to be certain you have adequate ventilation. This can be accomplished with a natural cross-flow of air through both high and low vents. Whenever possible, place the high vents on the side of the greenhouse opposite the prevailing winds. High vents should be approximately 15% larger than the lower ones. Greenhouses with dutch doors give even more control, allowing you to choose between the upper and lower portion when additional ventilation is needed.During the spring months, automatic roof vents are a must. They will open with the warmth of the day and automatically close at night when the temperature drops.
Cooling Fans
Air circulation in a greenhouse is so important you won't want to leave it to mother nature. When the air stills, it's up to you to regulate air movement with the use of fans. They can be inset into the wall of the greenhouse. You can also use free-standing fans or fans that clip to your potting bench an overhead support. Any of these can be moved around as needed.Misting
If you live in an area of high humidity, misting won't work because the air already has too much moisture, and it is warm (or hot) moisture at that! In less humid climates, misting can be very effective by adding a mister near an air-intake vent. Air coming in through the opening will make the mist evaporate which will cause a cooling effect. In addition, spraying water on the floor of your greenhouse will cause evaporation resulting in lower temperatures.Fogger
A fogging machine causes droplets even finer than a mister. The effect is similar but does not deposit as much water and has an even more effective cooling ability.Evaporative Cooler
If your greenhouse is used more as a solarium with furniture, misting and fogging aren't practical. In this case, a relatively inexpensive method of cooling is the evaporative, or swamp cooler. If your climate is on the dry side an evaporative cooler will work very well. However, in regions of high humidity, swamp coolers won't work at all.Air Conditioning
Although expensive to operate, an air conditioner may be your best solution. If you have a lean to greenhouse that is attached to your home, you might be able to vent your air conditioning directly into your greenhouse. If your home doesn't have air conditioning, install it for your plants. If you have a large greenhouse you may find it becoming the favorite hang-out spot for your family.Shade Cloth
Shade cloth is a must for any greenhouse and will work in conjunction with the other methods outlined above. To be most effective, be sure to put the shade cloth on the outside of your greenhouse. If you put it on the inside, the sun's rays will heat the side and roof panels and create an inward reflecting heat, like an oven. Placing the shade cloth on the outside, doesn't give the sun a chance to reach the glass or poly panels.Whatever combination of cooling methods you utilize, it's all about experimenting. Damp stagnant air will cause rot and mold so keeping that flow of air is of critical importance. Get yourself a good thermometer, keep a close eye on the temperature shifts - and Keep That Air Moving!