I want to report to the board on a great means of insulating for mash that I tried out today for the first time. I created an insulating jacket for my kettle out of a 1.5" thick closed cell foam camp mat, mated to the ever popular Reflectix.
I cut the camp mat to the size of my kettle, with cutouts for the handles and the spigot. I then hot glued a sheet of Reflectix to the outside of the foam, also with cutouts for handles and spigot. To the outside of the Reflectix, I hot glued three generic nylon lashing straps. This way, I can place the jacket around the kettle, clip the clips on the lashing straps and cinch them down tight, and I'm good to go. I created a similar two layer insulation for the lid, with another lashing strap that goes through the handle on the lid and through the handles on the side of the kettle to hold everything down nice and secure.
I did a brew day today, placed the jacket on prior to dough in, and tossed a moving blanket over the whole thing after I put the lid on. I had rock solid temps, losing about 0.7 degrees over a 70 minute mash. It was about 70 out this morning, so I don't know how well it will hold temps in the dead of winter, but I was very pleased with this setup today. I'll post some pics later.