Engineering Control Recommendations for Building Polytunnels that Stay Cooler During High Temperatures

Polytunnels (also known as hoop houses) are structures made of a metal or PVC skeleton covered with a sheet of thick, clear plastic. Polytunnels may be hotter inside than outside because sunlight passes through the plastic sheeting, heating up the air inside. Because polytunnels may be hotter inside than outside, they are often considered an outdoor environment by Cal/OSHA. 

The temperature inside a polytunnel can vary depending on its size, location, and time of the year. But the temperature inside polytunnels is often higher than outside of polytunnels. Heat inside of polytunnels may even become dangerous for both plants and people. However, polytunnels can be built in a way that prevents the temperature inside polytunnels from becoming too hot. As part two in our three-part series on heat illness prevention in polytunnels, we recommend engineering controls for lowering the temperature inside polytunnels. 

Image: Annemiek Schilder, Ph.D., Director, UCCE Ventura County/Hansen Agricultural REC