Rolling boil

[Matplat]

Holy shit balls, 5mm stainless!!!! No wonder it takes so long to get to a boil. Stainless is a pretty poor conductor of heat, for a metal, so I think you're right insulation will make a minimal difference. Still worth a shot though as its so cheap to do.

 

[koshari]

Just thinking about the insulation. It should help a bit, but the tank is made out of 5mm thick stainless. That has a huge thermal mass. I boiled it on Saturday night and it was still hot Sunday morning with no insulation on.

the thermal mass is one aspect but its the surface area of your entire vessel that contributes to the heat losses, and they become more apparent the more your mash temp is further than ambient temperature, ie at boil you will be losing the most. and yes as matplat said stainless isnt a great conductor in the scheme of things but we are still dealing with pretty substantial losses.