Comments inserted

"Tom" wrote in message

And the roofing felt has nothing to do with the
shingle's longevity, more so to help keep the tradespeople and their tools
dry
during early phases of construction, and as a second line of defense
against
ice dams.

Wrong. You are apparently not familiar with ice dams at all. Felt does
absolutely ziltch for protection against ice dams, you must use a water &
ice guard which is manufactured under several names.

A good roof _will_ last longer if it's allowed to breathe. A properly
insulated and ventilated roof can get away with NO felt underlayment at
all (I
think the building code writers may be in bed with some manufacturers!).

Yeah, don't use felt if you want the back of the tar strip to stick to the
decking. Felt is layed for a purpose other than a dry in feature as you
suggest.