U-values on Domes 1-layer: 5,36. 2-layers: 2,68. 3-layers: 1,70. 4-layers: Not available on round domes. 5-layers in acrylic: 1,03. U-values on plastic bases: Polyester base:0,94. And on the Steel bases there is no insulation , this you have to insulate self at site during mounting. So if you want to know the total complete U-value on a Roof Dome and Base , we have a program for this , contact us and we will give it to you !