[wernerb]

The hot water probably gets mixed with cold at the manifold, you do not put 70 degrees water in your floor.

What i dont understand is how it is efficient to deliver a constant 70 degrees heating pipe. There has to be some kind of boiler/trigger right?

[matsimitsu]

It's less efficient than lower temperatures, but this district is built without gas lines to the houses (as is normal in The Netherlands till recently), and it's more efficient than everyone having an electric boiler in their house.

The pipes are well insulated and apparently the energy loss quite manageable.

[abhibeckert]

The efficiency mostly comes from _moving_ heat that already exists, instead of creating new heat.

Depending on the specifics, that's often about 5x more efficient.

Counterintuitively - the "heat" source doesn't have to actually be hot. In theory as long as it's above absolute zero it can be used as a heat source to heat up the inside of your home. It's the same for cooling - even if it's hot indoors and really hot outdoors, you can still use a heat pump to make it even colder inside the hosue.