1.   Most balloon makers cover the outside of long-duration balloons with highly reflective plastic film, which slows the flow of heat in both directions.

2.   Reflective films can also restrict outside visibility and give the windows a shiny, mirrorlike look that many homeowners consider an eyesore.

3.   They offer greater outside visibility than reflective films.

4.   They are not as effective for reflecting heat rays as the less expensive reflective films, but they are as efficient in blocking ultraviolet rays and in reducing glare.