16 around the sideslopes 4 of the landfill containment cell 1 to form an insulative system having the configuration of a blanket it is anticipated in one embodiment of this invention that after its construction the casings 13 fig7 will be stored and shipped as a roll to the landfill site or the casings will be further subjected to manufacture by filling them with insulation and sealing them to prevent the insulation from coming out of the casing the latter method being preferred herein in the example of using casings 13 from a roll at the construction site various roll sizes can be employed the width of the rolls depending on economical and physical considerations of production storage shipping handling and installation alternatively the casings 13 can be cut into panels folded and banded onto pallets for delivery to the construction site in the case where the casing 13 for example is received on a roll at the landfill containment cell 1 a length of the casing 13 corresponding to the vertical length of the sideslopes 4 to be covered is cut from the roll the casing 13 is deployed so that the chambers 17 extend downwardly along the sideslopes 4 along the longitudinal or long axis of the chamber 17 once a number of casings 13 have been positioned over the sideslopes 4 of the landfill containment cell 1 the insulation 14 is filled into the chambers 17 to permit filling of the insulation 14 a fill opening 24 fig7 is cut into each casing 13 generally at one end of the casing 13 also provisions are made for.