I am going to cast a concrete slab for a cottage and have x number of XPS boards from before. It's enough for 1 layer in the slab. Maybe a stupid question, but should you have XPS at the bottom and then EPS on top, or should you have XPS on top against the concrete considering that XPS is supposed to be better against moisture?
How is the insulation value affected by having XPS in the slab, does it become better or worse? I understand that different products can have different insulation values, but I saw at Bauhaus, for example, that 50 mm XPS and 100 mm XPS both have 0.037 in insulation value despite being different thicknesses. Or is the difference in insulation value between EPS and XPS negligible, generally speaking?
How is the insulation value affected by having XPS in the slab, does it become better or worse? I understand that different products can have different insulation values, but I saw at Bauhaus, for example, that 50 mm XPS and 100 mm XPS both have 0.037 in insulation value despite being different thicknesses. Or is the difference in insulation value between EPS and XPS negligible, generally speaking?
The value they provide is the thermal resistance coefficient (lambda). The U-value for a product is obtained by dividing this by the thickness.
The XPS is generally stiffer and bears more load as well as being denser (extruded cells) than EPS (expanded cells). If the ground is worse, I would place it at the bottom; otherwise on the top as it's better for reinforcement. Common S100 EPS usually fractures and sags somewhat. However, both types withstand moisture.
The XPS is generally stiffer and bears more load as well as being denser (extruded cells) than EPS (expanded cells). If the ground is worse, I would place it at the bottom; otherwise on the top as it's better for reinforcement. Common S100 EPS usually fractures and sags somewhat. However, both types withstand moisture.
Dennis: Yes, that's how I initially thought, then I started to overthink and began doubting myself...
I was thinking about the age-resistant plastic that should be on the inside, otherwise moisture gets stuck in the wall going out. Then I thought about the better and tighter xps that should be closest to the concrete. Then my thoughts started going around again
Falkn: yes, that it's stiffer is an aspect. Now it's about a 50 m2 cabin so I don't know how important extra stiffness is. The ground here is very clayey but the idea is to dig out properly and lay drainage pipes so hopefully it won't get too wet down there either
I was thinking about the age-resistant plastic that should be on the inside, otherwise moisture gets stuck in the wall going out. Then I thought about the better and tighter xps that should be closest to the concrete. Then my thoughts started going around again
Falkn: yes, that it's stiffer is an aspect. Now it's about a 50 m2 cabin so I don't know how important extra stiffness is. The ground here is very clayey but the idea is to dig out properly and lay drainage pipes so hopefully it won't get too wet down there either