Cheap insulation. Is there such a thing?

Cat on a hot tin roof.

Good morning Trip... That's an interesting question.
I presume that your shop gets direct sun most if not all of the day essentially making it a hot box. What we have here is a cool Hand Luke scenario (sorry).

My first thought is shade, if you could provide shade to keep the sun off of your shop that would be a huge step. If shade is not an option. I would recommend installing an exhaust fan and fresh air vents to draw air through the shop which could help keep the heat from staying trapped inside the shop.

Insulation is also a good idea but keep in mind that it works both way (keeping temp out and in). I suppose you could go to the local DIY warehouse store to pick insulation up there. Some things I would consider:

* if the garage is dry you can go with either roll or panel.
* if the garage is wet I would stay away from roll because it could trap water.

I believe that one thing will marginally improve the situation alone. But a combination of air circulation and insulation will yield improved result. Better result will come from insulation combined with AC. Best result come from a combination of shade, insulation and AC.

I know that this info isn't an earth shattering revelation. It's just food for thought.

Take care.

AlV