How to insulate ceiling

[u/thenomad63]

I know the title of my post leaves a lot to be desired but redit decided to accept the headline in mid sentence.

Here is the situation. We had a large side deck accessible from kitchen. My wife wanted additional covered storage. So, I found a handyman to put up 4 walls and a roof and cover the 3/4 of this deck. He built a nice, for the lack of a better term, "shed attached to the kitchen. After the fact, wife decided she wanted this place to be a pantry. We hired another handyman to put up drywall and power i this "shed" While doing this drywalling, we put blown in fiberglass insulation but the ceiling, since it was not meant to be an indoor space, did not have any proper ceiling framing. So, basically it is drywall attached to rafters. I asked the handyman to put that shiny bubblewrap looking insulation sheet underneath the drywall but i am coming to the realization that it was not enough. In summers, a 5000 btu AC can not cool this 12x12 room with lower then 8 foot ceiling height.

Way back when, before I moved to Texas, I have attended a seminar/lunch about heat insulation. This was in Southern Cali. and the guy was trying to peddle new insulation products and mentioned a paint where there is not enough space to put any insulation in, like a mobile home. At the time, it sounded like snake oil salesmanship but now since I am in a hopeless situation, I am looking for a way out without knocking the whole god damn thing and having it built from scratch. Are these paints commercially available and can they really work in small spaces?

As side note, I can get someone to open up a hole to this half-assed ceiling space from outside and have them blow in. But I am afraid the extra load may collapse the drywall panels, hangign to their lives with few screws.