what have you got 4 inch pipes in your house
It depends on the temperature difference between the water in the pipe and the air outside the pipe (Newtons Law of Cooling).how much heatloss as a percentage of your boiler will you get for insulated pipes [and] uninsulated pipes
The OP was asking a general question; he did not say he was asking about the DHW supply pipes.well that's a different scenario...hot water primary and secondary pipes should be lagged as they are for a different purpose from supplying heat to rooms...
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