Preparing Window Jambs

Start by removing all of the fancy stuff from around your offending window, curtains, blinds, etc. (Blind brackets can usually be dealt with...so, you can probably leave those up. If not, take them down.) The aluminum extrusions must be securely attached to the window perimeter, because, as the film shrinks it applies considerable force to the extrusions and may pull them away from the jamb. Also, differential air pressures can be considerable over a large area. If you install the film on a badly leaking window you can see the film pulsate in a out with changes in wind (air) pressure.

Anything that prevents a good seal of the extrusion to the window jamb will compromise the effectiveness of the installation.The window jambs should be relatively smooth and flat for the extrusion material to mate easily with the window jambs. If you have a lot of high lumps and bumps or holes in your jambs or sill. These irregularities must be allowed for in the installation. The whole idea here is to seal the window opening from the outside air.

I have on occasion seen holes rotted in the wood sill wood and/or jambs. The system will still work but you have to move the extrusion away from the window sash or fill these holes. The extrusions should be caulked to provide the very best seal.

You can attach the extrusion to the wall around the window on the wall if you want(Black arrows in picture). Although this type of installation is possible and effective, it more or less makes the installation less desirable as far as looks.