How can I manage the temperature in my hoop house?
Answer: Hoop houses generally have no heating or cooling systems other than natural solar heating and natural ventilation. As a result, hoop houses provide less control of environmental conditions than full greenhouses. However, there are design techniques that can help control temperature?and also help extend the growing season?such as improving coverings, decreasing air leakage, and increasing insulation levels.The structure of the hoop house helps determine the interior temperature. A width-to-length ratio of 1:2 will produce the highest passive solar gain. Narrow tunnels tend to lose more heat because of the ratio of the perimeter to the total growing area. Taller tunnels tend to have better ventilation and air movement.It’s also important to choose the right covering. Greenhouse-quality polyfilm is superior to construction plastics like visqueen, providing more wind- and uv-resistance, better light transmission, and longer life. Polyfilms do lose ability to transmit light over time, however, and may need to be replaced according to the manufacturer’s warranty. Some people use a double layer of polyfilm, which provides slightly warmer temperatures and also provides increased protection against snow and wind. The downside of a double layer is reduced light levels.To gain additional heat from a double layer, you can use a blower between layers for extra insulation. And for even more protection, people sometimes use a low tunnel inside of a high tunnel, but it is important to closely monitor ventilation. To reduce interior temperatures in summer months, use shade cloth or remove the plastic covering from the hoop house. Shade cloth lowers the temperature in the hoop house and can result in less watering and also reduce plant stress. For more information, watch the ATTRA video Hoop Houses for Extending Your Growing Season, available at https://attra.ncat.org/video/. Topics include the uses and benefits of hoop houses, including increases in crop quality and yields; types of hoop houses; construction, materials and cost estimates; management of crops, soil fertility, pests, and weeds; and the economics and marketing of crops.Additionally, the ATTRA publication Sustainable Season Extension: Considerations for Design will provide more information on greenhouse design elements and their effectiveness at extending the growing season in cold climates.This publication is available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=370.