  Polymer-air multilayer (PAM) was developed to decrease the heat loss through
window glass panes. A PAM consists of a few polymer films separated from each
other by air gaps. Thanks to the excellent optical properties of the polymer
films, the visual transmittance of PAM is higher than 70%, and the haze is less
than 2%. PAM not only has mechanisms to reduce the conductive and convective
heat transfer, but also can obstruct the radiative heat transfer. With a 4~6 mm
thick PAM coating, the U-factor of a glass pane can be lowered from above 1
Btu/{{h}{ft}^2{{\deg}F}} to 0.5~0.6 Btu/{{h}{ft}^2{{\deg}F}} .PAM is resilient
and robust, relevant to the window retrofitting applications.
