Hi Alistair
I have a prototype of the same thing But I make it for the outside.
Thermal Transfer of cold through the Glass will Draft down from the
glass. Anything inside has this issue, The cold out side of the
window will cool the glass and once the cold is inside it is there to
stay until you can warm it up. The idea is great, Just campers makes
one that is ok but yours is custom. I recommend keeping the silver
side toward the glass since the microfiber will fade with sunlight,
Of course the amount of time you will use it per year means you
should still have it for years to come. Make sure to dry them well
before storage since the fabric is not mold and mildew resistant,
Maybe spray them with a water repellant to keep them from absorbing
condensation.
We have played with indoor and outdoor Thermal fabric for years and
outdoor is more efficient but as usual if parking in a area that your
worried about someone stealing your stuff then that is a issue as well.
Of course anything you do will help! don't get me wrong. and making
them affordable for the general public is a issue as well since cost
of goods and time are always an issue.
Fun Project for a weekend if you have the time, and know how to sew.

Have fun and good luck!

Jonce
www.fanchers.com
http://fanchers.com/59/VW%20Stuff.htm

>Binding/edging fabric tape (the black stuff you see around the pad,
>was used to make pockets sewn onto inside of suede fabric. Only 3
>sides sewn, magnets popped in and the 4th edge closed when the 2
>fabrics (suede and shiny stuff) sewn together.
>
>alistair
>
>
>On 2013-03-10, at 8:21 PM, forum email wrote:
>
> > As you are not going to mass produce these can you explain how you embedded
> > the magnets and how you sewed found them. (I say you but I obviously mean
> > your wife) (;-)