And when evaluating the insulation part for my investment, it would be good to know a few aspects:
- Thermal conductivity (λ):
This value may vary for both materials depending on the physical properties and density of the material. But, as approximate values, we generally find in the market λ = 0.022 W / mpK for polyurethane foam and approximately λ = 0.040 W / mpK for polystyrene. These values can vary easily depending on each manufacturer.
- Thermal stability:
Rigid polyurethane foam is thermally stable, does not soften or melt, the dissociation of chemical bonds begins only around the temperature of 200 ° C; while the expanded polystyrene begins to soften and change its properties around the temperature of 110-120 ° C.
For a short period of time, PUR / PIR foams can withstand, without side effects, up to 250 ° C; while polystyrene withstands up to around 80 ° C.
- Reaction to fire:
High thermal stability, its growth possibilities by changing the structure of the polymer and the use of flame retardants give rigid polyurethane foams superior fire resistance compared to expanded polystyrene.
- Resistance to chemicals::
Polyurethane foam has a good resistance in chemical environment and does not easily change its properties, while expanded polystyrene is more sensitive to the action of solvents based on oil or gasoline, certain adhesives or some insecticides.
- Easy assembly:
While expanded polystyrene requires adhesive layers, along with additional fasteners; polyurethane foam, either applied as such or part of a sandwich panel, is easy to apply, minimizing thermal bridges and ensuring good insulation of the entire building.
Expanded polystyrene is hygroscopic (retains water), which can lead to the appearance of bacteria, mold and fungus over time. While polyurethane foam has good waterproofing properties (does not retain, nor transfer water) and will protect the building for a long time.