Insulation, Radiant and Vapor Barriers - Hot Water Baseboard Heat pipe insulation

I need to insulate the supply and return header pipes for my hot water baseboard heating system that run through my crawl space. The crawl space is almost 10 degrees warmer than the living space above it. I am wasting money heating my storage area. Our Ultra boiler stops firing when the water outlet temperature is about 186 degrees F. I believe I can change that set point by about 20 degrees in either direction.
I have investigated my pipe insulation options. Closed cell ½” thick has an R value around 2.6 and can withstand about 220 degrees. The double foil insulation with the bubble wrap core has a much higher R value, the only problem is the bubble wrap will start to melt around 180 degrees. From a cost standpoint the foil is about 1/4 as much as closed cell. Rigid fiberglass with a foil scrim around it has an R value around 5 per inch and I think the cost is comparable to closed cell.
There are some areas in the pipe run where I don’t have much clearance between the pipe and solid objects so rigid fiberglass won’t work everywhere. I am considering wrapping the foil around the closed cell insulation to protect the foil from the heat and raise the R value of the closed cell.
Do you think this is a good idea?
Tom Elam

The closed cell will be the easiest to work with and I would try that first and see how things turned out. You might not need to add the foil bubble wrap. If not, you can always add the foil bubble wrap.