[buffalobillpatrick]

The idea of ODR is to match & minimize the water temp going to the floors to the expected heat loss to Outdoors. This is done so that condensing boiler, solar, or heat pump can provide the minimum temp water, this may minimize energy consumed, depending on pumping energy.

ODR is not perfect, but can be better than not using it. It does not consider wind effect or cold clear night radiation into space.

If not using any type of heat source that I mentioned, ODR helps little. I have done it both ways & currently do not use it as my current boiler condenses very little (very high altitude).