l am in the process of building my base for my new green house 6 foot x 10 foot. l have read in a book that a good ldea is to put sheets of styrofoam around the outside frame of the greenhouse 2 foot deep to keep the cold soil coming into the soil in the greenhouse. Is this safe to do? can or would any chemicals leach from the styrofoam.
A greenhouse needs to be freely drained and water movement in the soil levels out temperatures very quickly.
Also at that depth the soil temperature does not change all that much year-round, it is the top 30cm that heats up.