billb, that's mightily impressive. I don't know anyone else who can run their space heating with UFH for only 2 hours per day. I have experimented with mine for over 12 months, trying to run for say two/three hours in the morning and then two/three hours again in the evening but found this to be wholly ineffective
I now use my room stats to run ours for a 4 hour continuous block (longer obviously in the Arctic conditions of recent months), coming on at 3am. My experience is that running in two hour blocks doesn't generate sufficient & sustained heat into the screed in order for it to be released with any discernible impact on the space heating. I thought my current modus operandi was good compared to how I used the system initially, but I'm blown out of the water by yours. Most of my peers have rad systems and they can hardly survive by running for two hours only.