SIDE WINDOW SHROUD FOR THE AIRSTREAM INTERSTATE

"IT'S NOT THE AMBIENT TEMPERATURE - IT'S THE INCIDENT ENERGY!" a residential window salesman bellowed at me authoritatively one day many years ago.  I did not buy any energy-efficient windows from him that day, but he was correct.  What he meant was that most of the heat gain experienced in an interior space derives from the surface heating imparted by direct sunlight, rather from the temperature of the surrounding air.

And so it is as well with our Airstream Interstate.  Those big, beautiful black-masked windows become one hellacious heat sink on a hot Houston day.

No danger of something like this happening to our Interstate windows.  In southern summer conditions of direct sun, they literally become too hot to touch.  

A few weeks ago, I noticed that the Park N Ride buses running between League City and University of Texas Medical Branch (UTMB) in Galveston have had their windows completely masked with white vinyl, the kind of that have all those little holes in them so that you can still see out.  "Perforated mesh", they call it, and it's used for heat control.

Anyway, seeing those buses and also reading about Air Forums trailer owners painting their roofs with white elastomeric to slow heat gain... these things prompted me to tackle this little project in which I adapted a white nylon lining fabric into a shroud that can be put in place only when it is needed, which tends to be whenever the sun is broad-siding the vehicle as it is parked in an area where I am unable to turn nose-into the sun (which minimizes heat gain if one is able to accomplish it).  Given that the fiercest portion of the sun is only ever going to hit one side at a time, I made just one shroud.  My general approach went like this.

The cashier in Hancock Fabrics looked at me like I was a bit nuts for buying all that remained on a bolt of this stuff.  "How is it to sew?" she asked dubiously.  I told her that it sucks - it's uncooperative and slippery - but that I had no other choice for my application.

The window bank is about 14 feet long.  Rather than measuring precisely, I prefer to do these kinds of projects as fit-in-place, step-by-step.  So I initially fit it roughly like this to establish gross dimensions...

...and then lined it up on the tile floor of our great room to cut it down to size.

Once I had the top hem sewn, I taped the finished top edge in place and used the floor as a square guide for hemming the bottom edge.  This was more efficient than trying to impose quantitative measurements on fourteen feet of slippery, biased fabric.  

Now, a word about the neodymium magnets that I embedded in the edges of this thing (six along the top edge, six along the bottom).

No kidding.  We order them from the internet, and stuff like this really happens.  

These magnets are difficult to work with and if not managed properly, they will make your life miserable.  They Have One Job - to stick to whatever they can.  This includes the footer of my sewing machine, pins, scissors, and needles.  And the ironing board.  And the lamp.  And my belt buckle.  My watch band.  The dog's collar rivets.  The list is endless.

The neodymium magnet I prefer for this type of application is 8 mm x 4 mm.  Any larger than that and it becomes too difficult to break its mighty hold.  Any thinner than that and they shatter too easily, because they are brittle.  

I ended up having to insert the neodymiums into the top and bottom hems of the shroud as I was pushing the piece through my Singer, but due to the impressive forces they generate, I had to hand-sew each little pocket to keep them in their respective places.

And here is the result.

"It doesn't look as bad as I expected it to," my husband remarked.  My sweetie.  So much confidence in me.  

I had gotten that windshield cover some time ago from a Sprinter supplier - from one of the usual suspects.  It is both reflective on its outer surface and fleece-lined on the inner surface.  It works well but it is correspondingly bulky - about the size of a small blanket when folded up.  I wanted a much thinner side shroud because I probably won't use it as often - only when the sun is at its most brutal.  Therefore I was going for maximum bang for minimum buck, and in this case that translated into lowest possible mass and volume.

It folds down to about the size of a large ham sandwich and weighs about a pound.  Total construction cost was about 25 bucks, of which almost all was the cost of the 12 neodymiums.  

To avoid a neodymium nightmare, I quickly figured out that donning and doffing the shroud needs to be undertaken systematically.

I sewed in the neodymiums in the upper and lower hems directly above and below each other, and the best way to fold this shroud is to pick up the end pair of magnets, and fold them over to match up with the second pair down.  Then take what becomes the new end pair, and fold them over to align with the second pair down... oh, geez, this doesn't translate into English well at all...

Does this help?? Take the end pair of magnets, and fold into the second ones down, and so on. 

As you continue to fold, you should end up with something that looks like this:

So happy together - all the neos in their pockets are neatly together, and now this shroud can be slipped into a zip lock bag or some other container. Rather than having them clinging crazily to each other in a great uncontrolled neodymium cluster-freak.  

Anyway, that's my shroud story and I'm sticking to it.  Ferociously, like a neodymium magnet.

Update 20160615:  Augh, pound my head on my desk... Quite by accident, I found this surprisingly good quality metalized fabric at the Hancock Fabrics' close-out sale (they are popular in our area but are going out of business).

When what to my wondering eyes did appear... 

Historically, fabrics of this type have been novelty offerings such as one might use to create party clothing, not very durable but very expensive. In stark contrast, this was $2.79 a yard on close-out.  Technology has come a long way - this is quite strong and as light as crepe silk - potentially perfect for this application.  If I knew then what I knew now, I'd probably make my shroud out of this, betting that it would reflect even more energy than white polyester.  As it stands, I may use it to re-make the shroud because I'm quite curious about how it would perform.  Not that I care to hand-stitch 12 little neodymium pockets all over again, but I'm curious.

Moral of the story - check the store thoroughly before making a purchase decision.

Update 20160619:  I couldn't stand it - I had to do it.  I did an overlay sew of the metallized fabric on top of the thin polyester shroud.  It certainly looks better - a better match to the windshield cover.  How it will stand up I don't know, but it only cost me about $13 and some time to try this.  You can tell that this is not high-dollar fabric - it had some tension issues during production.  But as long as it works, that's not a concern to me.

OMG it's hot here now.  I set my iPhone down to add this shroud to the window after I finished the sew job, and by the time I got done, the iPhone was almost too hot to pick back up again.

It's got a bump toward the rear because when placed on this side of the van, it has to stretch over the porch light.