Insulating crawl space water pipes

[Case]

Our house has a crawl space underneath it through which the water pipes go.  Our pipes are PEX.  Im wondering if it is worth it to insulate them? I am almost certainly going to insulate the hot water pipes.  Our crawl space is not terribly cold (well insulated) and feezing is probably not a risk.  I have not yet seen condensation on the cold pipes.

I’ve seen websites arguing pro/con on this mini house project.  I have not seen hard math on the benefits.  I do understand the basic concept that insulation of pipes lets hotter water get to the faucet which lets you keep the tank at a lower T.

One last question is how to insulate the pipes where they come out of the tank, near the flue (gas heater)?  I know fiberglass or other thermally stable insulations are preferred... just trying to be careful since there is fire risk.

[CatamaranSailor]

In my location, you are required by code to insulate the hot water pipes in a crawlspace. Honestly, the insulation for pipes is cheap and you can do the job yourself no problem. It will make a (teeny tiny) difference both in your monthly bills and the temperature at the faucets. Probably not huge (for either) but it's still worth doing.

You actually lose a lot of heat through PEX...that's why it's use for radiant floor heating. Insulating it is a good idea. Since you are going to be crawling around in the crawlspace any way...go ahead and insulate the cold water pipes as well. Cheap freeze insurance. Also take the opportunity to look for anything else amiss...went spots in the dirt indicate leaks...rotten sub-floor or floor trusses, etc. I usually do a crawlspace inspection once a year regardless.

As far as insulating out of the tank.....there is a spacing requirement where code forbids it. 12" or something. Basically don't insulate the pipes coming out of the top of the hot water heater. Check your code for exact measurements.