There have been quite a few iterations of the "wind barrier" for the UP Plus printer, the latest of which is an adjustable flap to allow you to swap between air blowing over the print and not. The latest printers, so I am told, also have larger fans, which allow for even better cooling. Especially helpful during PLA printing.
Anyway, I've been occasionally getting "Nozzle too cold" errors when having the flap set to full open. It seems like the heater just can't keep up. So I thought I would try and do something to help insulate the element from the blowing air. What I have done is applied ( quite messily) high temperature silicone to the side and bottom of the heater element, but not the nozzle. I also applied it to the heater wires, that have a nasty tendency to break after a while, to help support them.
High temp silicone should be available at most auto parts stores.
So far so good! Even with the flap closed there is a small amount of air that escapes the barrier. This seemed enough to cool my hot end to about 98%. No problem really, its only when it gets to around 93 that it stops printing. So far the temp is reading 100% all the time, with or without the fan blowing on it. The other added benefit is that stray filament doesn't stick all over the heater making a nasty mess.