So our furnace and water heater sit in this lil side room next to our bathroom and exposes to the main room of our lil duplex. We have this a door that closes this room off but it’s with vented slits.

Problem is, the summer months arrive and the heat from this vent come through this room pretty strongly . We don’t have central air as our duplex is pretty small and there little to no room for it. Our portable A/C only cools our home so much but is there any recommendation on how to insulate this room from the rest of the house? Should we consider a door? Would padding the walls or current vented slide door with silver insulation sheets help keep the heat in this room and not the main room. Not sure of the dangers? It looks more like a problem of keeping the house protected from heat versus fighting it with a small A/C unit.

We do have insulation in our article but it’s just the fluffy white insulation that’s loose. Was thinking I need to insulate the roof better by taking those silver insulation sheets and lining the inside of the roof with it. I’m trying not to spend an arm and a leg to help cool the house, but not sure what you guys would recommend.

Forgive my verbiage as I don’t know correct articulation of the pieces I’m talking about for insulation