Walt Chase wrote:A place I worked at many years ago had several glass greenhouses. We were located in middle GA in probably zone 9. We always "whitewashed" the glass greenhouses each spring. Mixed it up and applied with a garden sprayer. They make a special coating that goes on and over the course of the season slowly washes off the glass. It definitely kept the GH cooler than the bare, clear glass. I don't know where to source that any more or if it would be compatible with plastic covering on a GH.