Final answer:
Using glass as a covering for greenhouses can lead to thermal stresses and potential cracking, create issues with partial shading affecting plant growth, and involve environmentally unfriendly chemicals in its production phase.
Step-by-step explanation:
There are several disadvantages to using glass as a covering for greenhouses. First, glass can cause thermal stresses due to its high thermal expansion and poor resistance to sudden temperature changes. This can lead to cracking or breaking when there are rapid fluctuations in temperature, posing a risk to the structure's integrity. Secondly, glass is susceptible to partial shading, which can be disproportionately disruptive to plant growth as it can block sunlight required for photosynthesis.
Lastly, while not directly related to its use in greenhouses, the manufacturing process of glass, particularly soda-lime-silica glass commonly used for windows and similar applications, typically involves the use of environmentally unfriendly chemicals. These chemicals can negatively impact the environment during the production phase.