I have a hot water recirculation system that is currently insulated with regular 1/2 inch thick foam pipe insulation. Both the hot and the return lines are insulated. Altogether there is probably about 180 ft of pipe in the crawl space under the house and it is fairly accessible. I live in the foothills of California and the crawl space ranges from around 55F in the winter to 70F in the summer. I think it is a significant part of my heat loss resulting in a few hundred dollars of propane burned each year to keep it warm. Without recirculation it takes a full two minutes to get hot water in the master bathroom. I see about a 25F temperature loss through the circuit starting at 125F but have no way to measure the flow but it's quite low (gravity feed in the summer with the water heater in the basement). Every form of regular pipe insulation is pretty expensive to put over the existing insulation so I was thinking of using regular 2X4 wall fiberglass insulation with kraft paper on one side, cut into short pieces, wrapped around the pipes and secured in place with tie wraps. That appears to be very cost effective with a decent R value since a 25ft roll of insulation will do about 32ft of pipe for less than $14. Has anyone tried this?