Insulation in Floor Slab With Fibreglass Roll? Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[Tonyonly]

Can fibreglass roll insulation ever be used in a concrete floor slab? Does it lose its effectiveness when compressed?

[welsh brickie]

fiberglass does not have the same insulation value as board insulation, plus it compresses reducing the insulation value even more. And the moisture would destroy it.
It is not permitted to lay it under the concrete slab