Pipe insulation

ive done some searching on the site and i keep getting the old if the pipes are in the house its heating the house dont worry about it, however my basement is cold and drafty and unheated. im on an insulation kick after insulating the shop and noticing a huuuge difference. heres my plan, insulate the floor joists with an r-13 leaving an air gap between floor and insulation to slow down the cool air transfer, then insulate all the pipes in the basement to keep it a cool space. and insulated all exposed lines in the shop (maybe, maybe not.) curious to see how many guys out there have done this, and is there a noticable savings here. on a heat loss calculator, an r-13 in the floor joists cuts down the heat load by more than 25% ! thanks, Paul

just did some quick math, i figure about 800 to do the project total. at 3 skids a year (probably will chew into a 4th because im REALLY enjoying a heated shop), its about a 3- 4 yr payback. sounds too good to be true?

insulate the floor joists with an r-13 leaving an air gap between floor and insulation to slow down the cool air transfer, then insulate all the pipes in the basement to keep it a cool space.

I've did the opposite in basement for a reason. Moving my heat source to work shop wife wasn't fond of having a cold basement. What I've done was insulate all of my iron piping from coal boiler to oil boiler in basement. Then I removed three 2 ft section of insulation to help take dampness out of basement. Note I've didn't insulate copper lines on oil boiler side. Now wife is a happy wife with warm feet. Before removing some insulation I've got this from wife ___>

lol thats what slippers are for tell her!!!!