Choice of foam insulation for a conservatory

[Viqtory]

I have an existing conservatory that I was planning to insulate on top of the existing decking. Should I choose XPS or is EPS good enough? There is quite a difference in price. On top, I was thinking of some kind of paper or fabric and then new decking on that. Total novice in construction, so grateful for any input

 

[huggan]

XPS can withstand more pressure and is unnecessary for the use you will have.