It depends on your oppinion of hot water. Doctors say for houses with children, no higher than 130 degrees F. To reduce scolding. That is no where near high enough for me though. Just change to higher if you need hotter water.

To be safe 120 under for tub and sink .For heating the home 180 or under.

The DIY television station says 110 degrees

First, is this the run temperature thermostat, or the safety thermostat.
If it is the run thermostat, then you also need to qualify your heating radiation.
If it is base boards, then the run thermostat needs to be around 180.
If its in floor then no more than around 100.
If it is the safety, then set it 20 degrees higher than your run temp.
Now if your using this for domestic hot water, then set to 120 for a run temperature.
If your still in doubt, call a professional HVAC contractor.
Also, YES, insulate the pipes.

For Heating Only 180 Degrees Domestic Hot water 120 degrees

If you have children it should be set at 120 to avoid scalding.