tempature isolated Cabinet grow box idea

Hello everyone i wanna build small cabinet 70x40x38 cm and i wanna put it to my garage where tempature Is almost same as outside (little warmer) So i need to isolate it very good. Im thinking to paste some isolation polistirane (like isolation used for houses) outside of the cabinet And put door insulation strip between the doors. I wanna use some led bars on the side And top. 2 PC fans with carbon filter in the walls of the closet to bring And exhaust air. And for warming the air i Will use the 55w ecoheater hylite 55w. What do you think Will be it enough? Thank you very much

Sounds fine. I would go bigger. You will wish you did later when space becomes a premium.

Make sure you insulate all surfaces including the underneath.
Possibly mount your driver inside too if you can afford the room. That will add a bit of heat.

Those heaters have to be mounted horizontally.

Hard to say if you'll be able to keep it warm enough, we don't know if your winter lows are 5° or -25°. Insulation becomes less effective as the plant gets bigger and more air exchange is needed to keep humidity in check. A heat mat can help keep the pot warm.