What insulation values can be achieved with spray foam?

Spray foam insulation can offer virtually any insulation value required, simply by altering the depth of the foam you can achieve as little or as much insulation as you require. As a rough guide, foam insulation offers around twice the insulation values of mineral wool, a roof without felt can be insulated to current Building Regulations for loft conversions with around 100mm of foam insulation on the roof alone.