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That's a pretty good idea. I have some of that foam insulation with the reflective facing, I should try that.

He could avoid the excess of light inside the room doing something like that all around the plant.

Ofc, but that takes more effort :D sticking some reflective things on the walls takes 20 seconds.

Smokers thoughts hehe.... Or you can do it easy mode with raft wood sticks and glue, very cheap too.