The windows in my house are just not suitable for a window air conditioner. Several years ago, I bought a roll-around air conditioner shown in the picture below.

If you have one of these, you know that it vents the hot air out through a duct that goes from the back of the unit to a nearby window. One problem with this arrangement is that the duct gets fairly hot. I have always felt that the air conditioner can barely keep up with the heat it is generating itself and putting into the room because of the hot duct.

After about 5 years of ownership of this unit, I finally had a bright idea. Today is the first day it has been hot enough outside to see if my idea works. It does.

This gives away the surprise of the air conditioning solution

The duct measured 5 ½ inches in diameter. I bought duct insulation for a 6 inch duct. Now the duct is room temperature, and the air conditioner does not have to fight itself. The insulation cost me all of about $8. The insulation is too bulky for the air conditioner manufacturer to have packaged this cheap solution with the unit. They could at least have mentioned it in the user manual. It has made me go from a rather unhappy owner of such a unit, to a completely satisfied one. I may just buy another unit like this one for upstairs now that I know how to make it work.