Am living in Lahore, Pakistan, and these days in process of my house construction. Note, here locally we have concrete flat roofs. Summer time maximum temperature upto 50C, and in winters minimum temperature -1C. Looking for a Insulation board for my concrete roof top.
Traditional way, is that over the concrete slab , a layer of molten bitumen is laid with a Plastic sheet over it to water proof the roof, then a mud layer of about 6" inches is applied, over the plastic sheet, and over it clay brick are grouted with cement. The mud in this scenario is supposed to act as thermal insulator.
I am looking for a more efficient way than described above. Local vendors are offering EPS ( Expanded Polystyrene Sheet ), and XPS ( Extruded Polystyrene sheet ) boards. In both cases vendors recommend a 2" ( 5 cm ) thickness of these boards.
Installation method as described by vendors is quite similar too : (1) Concrete roof slab (2) molten bitumen layer with a plastic sheet over it (3) Lay the EPS or XPS boards (4) another layer of plastic sheet (6) 6" inches of mud layer (7) clay bricks grouted with cement over it.
My query is that out of these 2 options : EPS and XPS, whichone is better, as price difference between the two is about 50%.
Thanks & Regards. Omar