Joel,
I borrowed this input from another forum because I thought it was good info and relavent regarding MCD shades. We put a single powered one in our front windshield and it is a compromise but maybe not as much as one would think. When it is vey sunny and hot we will lower it some and slip a bubble foil faced traditional windshield shade in front of the MCD for reflection and some insulation and lower the shade the rest of the way. That seems to help quite a bit. We are happy with this compromise for the convenience, privacy, and the heat reduction that we do get. Here is the post...
I would like to add some comments regarding the exterior and interior covers. A couple of months ago I purchased a full set of MCD Duo's for the coach along with the wheel covers. They are a nice addition, well made, look good, easy to operate and expensive. I also spent almost 2 weeks at MCD parked directly facing the Southern sun in 110 degree + weather and as I was bored to death most of the time so decided to take heat measurements to test each of these setups during the day.
My wife hated the pleated shades which most folks don't like and wanted the upgrade because of looks and reduction in heat intrusion into the occupied space. I have over 25 years in the A/C trades so I knew a bit about the subject and tried to explain that there are 3 forms of heat. Radiant, conductive and convection and the interior shades would do nothing more than reduce the radiant heat waves. The interior shades will actually heat up from convection (hot air currents circulating between the hot windshield and the shade itself) and will give this heat off to the interior of the coach. This was proved by taking temperature readings as there was a reduction in heat but not great.
While waiting for our shades to be made I asked MCD to loan us an exterior shade which we installed across the windshield. The temperature on the inside of the glass was approximately 10 degrees warmer than the room temperature within apprximately 1 foot from the windshield. As the temperature drift was up to almost 90 degrees by late afternoon it placed the temp in the cockpit area over 100 degree. The glass was hot enough to fry an egg on, the reason for this is conductive heat from the exterior screen itself. The screen lays directly on top of the glass and transfers this heat to the glass. Without an air space betweenthe two the heat has no place to go but to the glass and into the coach. The radiant heat though does not make it through the screen for the most part.
As far as which is better for heat reduction, I would say they are a toss up, they both reduce radiant heat, one conducts heat through conduction (exterior) and the other conducts heat through convection (interior.) Of course the MCD's are nicer.
I linked a couple of pictures of an Airstream TT and I took notice of the shades on it manufactured by Airstream. You will notice that there is an airgap between the shade and the front window. THIS WILL DO THE BEST JOB. If someone can figure out an easy way to keep the exterior shade off the window (so there is an air gap) they would then have the best heat reduction method of all.
Hope this helps.
Later Ed
