Building Better Greenhouse Shading
Tests have shown up to 30-percent lower greenhouse temperatures with the use of light color or aluminized-material shade fabrics as compared to traditional dark-color materials, due to reflection of solar heat.
1. Choose exterior shade for free-standing or hoop houses.
Low-cost shade compounds can be sprayed or rolled on the glazing at different levels to achieve constant light reduction. Select a material specific to your glazing that can be easily removed in late fall to allow for full winter sunlight. Shade fabrics applied over the greenhouse roof are lightweight, easily applied and available in several materials, shade levels and colors. Most materials are ultraviolet (UV) stabilized, and will last about 10 years and cost roughly $0.25 to $0.50/square foot, depending on the type of material and the shade percentage.
2. Choose an interior movable shade screen for gutter-connected houses.
Interior screens provide shading and heat-energy conservation. When retracted on cloudy days, they provide maximum available light for photosynthesis. When closed at night during the heating season, they save up to 35 percent of heating costs. Shade screens also reduce condensation on leaf surfaces. Select an open mesh for greenhouses with roof vents or closed mesh for exhaust fan-cooled houses. Translucent materials provide some shade and can be left closed during the day for additional energy savings.
3. Factor in cooling capabilities.
Research at North Carolina State University and Rutgers University has shown that additional cooling can be achieved by misting to keep the shade material wet. This is achieved by evaporative cooling. Air movement from wind and horizontal air flow (HAF) fans can also impact the cooling effect. In the future, photoselective materials may offer less heat gain, better plant growth and fewer pest problems.