Poliuretan foam. Polyurethane foam foam should be filled with a trench around the perimeter of a well below the level of freezing of the earth. All work is carried out in winter at a temperature of -20- -30 ° C, which allows you to save on foam. A dried foam must be protected from ultraviolet rays without fail — this can be done using a layer of paint. When digging a trench, it is necessary to take into account the diameter of the well rings, groundwater level and the level of freezing of the Earth. Insulation of polyurethane foam foam is considered the most budget option and will not take much time for execution.