Best way to insulate external sump

[pledosophy]

I am going to be placing a sump in my garage. The garage has large temperature swings, 40F to 115F. I plan to put the sump in it's own cabinet and insulate it on all five sides (under the cabinet as well). I am not worried about seeing into the sides of the sump. I will put a 1/2" acrylic lid on top of the sump as well with a hole cut out for the top of the skimmer.

What is the best insulating I can use for this application?

Foam board? Fill the whole thing with great stuff? The reflective roll?

Even with the precautions I am taking, it will have higher humidity and I would like something that can stand up to that and not grow mold.

Appreciate the advice.

Thank you!

 

[Snoopy 67]

I used 4" foam around my AC unit in the attic because water used to condensate inside & run out the vent. NO MORE!

 

[FUNGI]

IMO....

FOAMULAR NGX F-150 1 in. x 4 ft. x 8 ft. SSE R-5 XPS Rigid Foam Board Insulation​

 

[Kingsley_Reef]

+1. Rigid foam is probably your only answer

 

[PapaFishRocks]

+1 Rigid foam board.

(Spent 9 years in Operations Management of a foam board manufacturer)

 

[pledosophy]

Is one better than the other? I have used the Pink Panther one before. Seemed good. But it was for a shed not a sump :D