The simple answer is yes, and some form of temperature modulation is always required for greenhouses. Temperature control not only compensates for seasonal variations, but also ensures that plants will tolerate the heat from afternoon sun in the summer, and will not be growth-stunted by cold air during the winter. However, there is no available form of insulation that can protect greenhouses from extreme heat or cold without supplemental heating or cooling. Double wall plastic covering on a greenhouse frame, with an air pocket between the layers, offers a degree of insulation in moderate climates. Bubble wrap can be a cheap solution because it can be stretched under a greenhouse frame as a second layer of protection. Used in this way, and installed with temporary clips, the bubble wrap will seal air gaps and provide a sort of double-glazing to reduce heat loss. Specialty horticultural large-bubble wrap sometimes also has added UV protection. Any such insulating material reduces, to some extent, the amount of available light, and it can have an effect on plant growth and maturation schedules. In areas with winter snowfall, greenhouse design is critical. Snow itself is an insulating factor, but most flexible greenhouse film will not support heavy snow load.
Shadecloth, designed to filter the light, provides another form of insulation during summer months, and it offers some protection from daytime heat buildup and extended hours of sunshine in some parts of the country, particularly the desert Southwest. Specialty Agricultural Shadecloth, available in many sizes, colors and densities, is also water-resistant and typically offers protection from harmful UV rays. It is lightweight, relatively easy to install over the greenhouse frame and equally easy to remove and store during winter months. Shadecloth is formulated to block between 30 and 90 percent of the light, Depending on the type of plants being grown, Shadecloth will also moderate greenhouse temperatures and contribute to a better growing climate. Quality shadecloth, if cleaned and stored properly, will normally last between six and 10-12 seasons.It will also help extend the life of the plastic film being used. It is important to analyze the percentage of light you wish to block; that will depend on what crops are growing and their specific light needs. For most plants, a reduction of 50 to 60% during the height of summer sun should be adequate.
