Not sure where you got the idea that there was no under-soil heating at the Stadium of Light. The following is taken from details of the pitch on safc.com: "The under-soil heating, which is used to keep the frost out of the pitch and also stop the snow settling on the surface, is situated at the bottom of the lower rootzone. This means that the hot water in the pipes, which is up to 30''C when it leaves the boil under the stands, does not get the roots of the grass too hot which will dry them out and cause them to die. Electronic sensors in the pitch to tell us how hot the rootzone is and how much moisture is present. When we use the heating system we make sure that the upper rootzone does not get hotter than 10''C. If it gets too dry the pitch can be watered with the irrigation system."