The roof vents!
The roof vents is where all heat and cooling comes in and escapes!! All the lid is plastic and it just 'sits' on the frame. It is not insulated in any way. And if you have the white ones the heat coming in is unreal.
I have 3 roof vents and once I put the pillows in you could FEEL the difference just standing underneath it and in minutes you could feel the difference in the inside coach temperature.
Made for an RV and they fit right it. The best ones are the ones with the "silver foil on one side and cloth" on the other. The rubber type ones suck, look tacky and don't work as well.
Put these in your roof vents and sit back and feel the difference in summer AND winter. :C


This is the 'Sun Shield' one with the silver backing that blocks "100% of UV rays". IMHO the best one to buy to keep the heat out.

""
The Camco Sunshield RV Vent Insulator fits snugly in an RV vent opening with a full 3" of foam to help stop heat transfer, keeping your RV cooler in summer and warmer in winter. The reflective surface blocks 100 percent of the sun's damaging rays, keeping you and your belongings protected. This Camco RV vent cover insulator fits standards 14" RV vents and is a smart choice for passive climate control in your vehicle. This insulator is designed with reliable insulation that will last as it keeps you comfortable for many seasons in your RV""http://www.walmart.com/ip/Camco-SunShield-RV-Vent-Insulator/29764495?action=product_interest&action_type=title&item_id=29764495&placement_id=irs-2-m2&strategy=PWBAB,ABTV1&visitor_id=&category=&client_guid&customer_id_enc=&config_id=2&parent_item_id=29764495&parent_anchor_item_id=29764495&guid&bucket_id=irsbucketdefault&beacon_version=1.0.1&findingMethod=p13n