How to choose a floor insulation?

When choosing floor underlay , the following should be taken into account:

• the condition and unevenness of the concrete
• the need to insulate and improve the acoustics of the sub-floor
• the need to heat the floor (particularly important in case of basements and ground floor rooms)  
• load resistance of the floor insulation (greater load resistance increases the life of the floor). 
• protection of the floor against dampness and from damage caused by fungi and mould