Deb and Ed M wrote:
I had sheets of Reflectix insulation cut to fit each window; plus the foam pillows in each vent made all the difference in the world!! On our 5th wheel, we could also screw the A/C vents shut, so heat wasn't being lost up the ductwork (and I also put a layer of Saran Wrap over the A/C grill screen, too)
Those pillows work well. The new ones have reflective material on one side to make the pillow last longer in high UV conditions.
If you can get a roll of Reflectex, you can cut it to fit in just about any area under the cabinets too; just keep it clear of wires or heat sources.