The u-value of a material shows its ability to conduct thermal heat. A material with a high u-value is very good at conducting heat and will therefore let most of the heat in on a sunny day, whilst letting most of the heat pass through when it's cold.
The standard polycarbonate roof used in most conservatories has a very high u-value which is why conservatories can be uncomfortably hot in the summer, when solar heat is conducted into the room, and difficult to heat in the winter when the same ability to conduct heat means little of the generated heat remains inside.
Conversely, materials with a very low u-value are much better at insulating a conservatory, keep it cooler when it's warm outside, and making the room much easier and cheaper to heat in the winter months.

The Roof Revive System uses a light 28mm high-performance composite insulation, combining 19 layers of reflective and insulating materials to deliver its stunning results. The system is installed with adequate cross ventilation to prevent condensation or 'sweating' of the structure.
Following careful installation, the roof is finished with 10mm plasterboard and skim finish. The customer can then apply an array of decorative finishes to the surface to fully complete the stunning new installation.
No alteration is made to the existing conservatory roof or to its vaulted profile, resulting in only a minor 40mm reduction in headroom.