Where to buy 2'x4'x 24mm expanded polystyrene board qty~160 pcs distribution price?

Planning to improve house ceiling insulation by installing the EPS foam. Lately the weather is scorching hot and the heat radiate from roof to the room.

Which I suspected causing dizziness in the family, or due to the heat the ceiling particle board is emitting fumes that is not good for health like Formaldehyde.