A High Quality Cover
Whatever system you use to heat your greenhouse, it’s important to provide as much insulation as reasonably possible. In cold climates, allowing carefully warmed air to pass out of the greenhouse through poorly insulated panels or even outright gaps could spell the difference between success and failure in your crop.
At the most fundamental level, your greenhouse is a frame covered by a translucent cover that traps warm air inside while allowing sunlight through. Being clear, it may be easy to overlook, but your greenhouse cover is probably the most critical element in your success or failure.
Films or panels used for your greenhouse cover need to allow plenty of sunlight through, but it also needs to be lightweight, durable, able to withstand constant UV exposure, and easy to install. It should be resistant to punctures and tears from normal activities, as well as easy to repair or replace if damage does occur. The best covers are easy to ship and available in custom configurations to fit your specific design. BTL’s Armor Clear meets all these conditions and offers a unique anti-condensation layer that promotes more even light distribution.
Double Walls
If you plan to use a cover on a geothermal greenhouse rather than glass or polycarbonate panels, you will need to invest in a double layer design to prevent heat loss. Some configurations use a fan to inflate the space between layers and maintain a dead air space as insulation. It’s also possible to build a passive double-walled cover where the layers are held apart by the frame if there’s no electricity, but it’s better to use a battery or solar-powered fan because inflated double wall structures just work better than static ones.
Infrared Additive Films
In addition to choosing a durable outer greenhouse cover, you may want to consider installing another layer of infrared (IR) additive film or a spray-on coating inside the greenhouse. These films and coatings reflect infrared heat back into the greenhouse as it tries to radiate out through the poly film cover. These materials work best when paired with poly films rather than glass or rigid panels, and in fact they can reduce heat loss by up to 35% on a clear night. This simple addition makes poly films nearly as insulated as glass at a fraction of the cost.
Condensation Control
All greenhouses have the potential to develop condensation issues, especially in winter. As heated air hits the cold barrier of the outermost layer of poly film, water rapidly condenses and may rain down on your plants or make everything muddy. Wet greenhouses tend to develop rapid cases of powdery mildew and other diseases, even when you’re keeping temperatures relatively cool over the winter. Heat pumps have a drying effect on the air they process, so ground-to-air or water-to-air systems relying on this equipment may mildly dehumidify the greenhouse. However, direct air circulation from underground is more likely to increase condensation rather than reducing it. While humidity doesn’t automatically result in mold issues, it’s still not pleasant to have water dripping on the back of your neck while you thin your sprouts. Installing dehumidifiers near the air supply can help, but it’s important to consider all the ways condensation can cause problems. BTL’s Armor Clear greenhouse covers actually offer a specialized anti-condensation layer that prevents water drops from forming on the roof and blocking incoming light.
