Foam is the best insulation particularly when compared the other insulation both in the perspective of qualification and using life span. Usually, foam would not absorb water but as foam has low melting point, so that it would be able the change in shape when contact with high temperature. But when we use foam for the general roof of houses, offices, and Industrial plants, it would be regarded as the best insulation as when working on that area, the temperature is not high for that level, except only when installed in the sunshiny area or the area that  high temperature of more than 100oC which would resulting in the absence of shape retention capability when has none of internal frame that use to attach. However. type of foam  that we use currently has varied and able to classified in several classes, but the most popular class of foam that use in the work of construction has at least 4 classes described as follows:

1) P.U.FOAM(Polyurethane Foam)

     Polyurethane Foam is CHFC-141b substrate that spray out in the appearance of foam, wich has both classes of solid mold by injection molding foam or spray on the surface as rigid foam is one of the materials that is very low rate of heat conducted condition(K-Factor) as it is produced of HCFC-141b Substrate that has heat conducted condition lower than in the air,. Mostly, for the manufacturing of general insulation  must cover with the material that has the property of fire retardant, but P.U.FOAM is compounded with inflammable substrate in itself. P.U.FOAM has the structure of close cell so that made it capable for better resistivity for humidity in eithet cold  storage or water leakage on the roof better than other kinds of insulation.

2) P.S.FOAM(Polystyrene Foam) 
       Polystyrene foam has produced and classified into 2 forms:(1) Extruded form, and(2) molded form, However, as the nature of P.S. Foam is produced of natural cell which is flammable material, so that why we have to wrap or cover by corering material that has better qualification of fire retardant when bring to use such as foam that use in cold storage must articulated together with metal sheets. Moreover, it must be careful and keep foam direct contact with sunlight as UV. in sunlight will cause annealing of foam and change in form. This kind of insulation is manufactured by interconnected together with small foam cell so that left some spaces during these cells. Thus, the resistance of water penetrated capacity  will be high or low is mainly depending upon the bulk density of foam also.

      Elastomeric foam Expanded rubber foam is the kind of insulation that has the qualification of elastic by air injected  ad expanded in mold. This is the reason why this kind of insulation also has the structure of close cell, that is to say eac cells inside hill be tight connected to each other, that is the reason why this kind of foam is able to resist the capable of water leakage effectively and according to the main advantage of low rate of water absorption, then suitable for use with low temperature work space like in the system of piping connection that has the optimal low temperature However,the performance of insulation would be decreased dince foam is contracted when applied in the low temperature environment for along time 

4) P.E.FOAM (Polyethylene Foam)

       Ethylene is the insulation that produced from ready-made P.E.foam sheet manufactured with low density polyethylene substrate(LDPE). The main qualification is that is able to recuce heat and noises coming from external area of building. Moreover, it is also use to install before roofed by using together with  coherent material (gum) by extruded and pressed with selected roof. This kind of insulation has the value of heat resistivity or K-Factor approximate with glass fibre and cellulose fibre at equal level of bulk density