The main problem with the use and matching of different kinds of slag wool as a floor insulation for the first floors is its ability to practically full lose its heat insulating properties in the soaking. After that, the material becomes in absolutely unsuitability during several seasons. It ceases to retain the heat and requires immediate replacement. This problem leads to an instant decline in the quality of life, so adherence to special requirements is an important practical task. The purpose of this article is conduction a detailed review of slag wool as a floor insulation for the first floors, including its classification by the type and the form of release, consideration of the most significant advantages and disadvantages of its various types for generalization and formation of both practical recommendations for eliminating the drawbacks of this material and the optimal technology of insulation of the first floors with slag wool. The main advantages and disadvantages of using slag wool have been revealed by the method of information analysis. Practical recommendations for minimizing the impact of negative factors of this material on human during matching and direct use as a thermal insulation have been given. Step by step optimal technology of the first floors insulation with slag wool based on studying the material features have been formed and described