Polyurethane Spray Foam Insulation R Values
Polyurethane Foam has the most efficient thermal insulating value of
any insulating material used in general building construction.
The typical 'aged' K factor - Thermal Conductivity of
Rigid Polyurethane Foam is 0.025 - 0.030 W/m.K.
The 'aged' K factor means that the Thermal Conductivity value
that the foam layer will exhibit under 'diffusion' conditions,
that is, when both sides (not edges) of the foam layer is exposed to air.
The R-Value – Thermal Resistance on this basis is set out below.
| PUR Foam | R Value* |
| Thickness (mm) | m2 .K/W |
| 100 | 4.00 |
| 50 | 2.00 |
| 25 | 1.00 |
As the system is sprayed in-situ, it forms a continuous thermal barrier - no 'thermal bridging' from gaps, fasteners, etc can occur.
There are numerous types of insulation available and some are listed
on the graph.
The graph has examples of the relative thickness of alternative building
materials needed to match the thermal conductivity properties of polyurethane
foam at 50mm.
Comparison between different insulation r values using thickness
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