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Thinking of using fiberglass water heater blanket for insulation, with reflectix over it. Has anyone tried this.  What is your opinion.  want something effective and simple to install especially in all the nooks and crannies of the van walls.

Also, if I use foam insualtion and reflectex, will the reflectex act as a radiant barrier if put over the foam.  I am thinking foam on the walls, and reflectix attached to the ribs over the foam.  would that work?????
The mylar part of Reflectix does nothing at all, unless installed

facing outward to reduce radiant heat from coming in

ideally with a 1" air gap between it and the outermost skin.

Plain plastic will be cheaper and stronger as a vapor barrier, preventing convection, infiltration, air movement between inside the envelope and outside. Located between your inside skin and the insulation layer.

Fiberglass batting is not as effective (R-value) as rigid foam like polyiso and can retain moisture.

For maximum effectiveness use closed cell two-part spray foam to fill the gaps and corners, in effect striving for the insulation to form as complete an envelope as possible.

Also insulate over any metal bits to prevent conduction, thermal bridging.

If you're following the 60's much of this is overkill.
The most effective method is foam on the walls, roof, windows at least 1.5 inches thick on the roof, I have about 2 inches on the windows and 1/2 inch on the walls. The more foam you use the better performance you get, but there is a limit in how much interior space you want to give up.

But that in itself is not good enough, you also need to build a wall to separate the front driver compartment from the rear of the van. I built a sliding foam door. Also if possible foam the side and rear doors, maybe something removable. You need to prevent as much outside air from getting in your van. To me that is the more important part, keep that outside air from coming in your van. Some people dont want to cover up there windows but that is where alot of the cold comes from. 

Just doing that I get a 10 degree difference from inside/ouside of van. Its january and I still havent used a heater, I havent even had to sleep in my sleeping bag. The winters are mild here in california, the lowest temp I seen was 42 degrees, inside van was 52 thats with no heater. Before I covered the entire rear of my van in foam, I had to use the heater and many a times slept inside 2 sleeping bags. 

The heater blanket you can use it over the foam to cover any gaps. I never use the reflectix. The rtech foam I use already has a reflective side.  

Foam is very effective if you use alot of it.

rtech foam that I use, it cost about 9 dollars at home depot for 4x8 foot 1/2 inch sheet. Easy to cut with a boxcutter, I installed with a hot gluegun.

I have used (am now using) the reflective style water heater blanket on my windows.  Cut it to fit, sealed the edges with gorilla tape.  My RV has the pleated day night shades and I just shoved the blanket covers behind the shades and they stay in place well.  Works much better than reflectix but storing them takes up a LOT more space.

As for walls etc, I defer to those more knowledgeable.
So, every time you are saying "foam" you are talking about the Rtech?
Who are you asking?

Rigid panels are different from pourable or sprayed expanding foam.

Among rigid, XPS, EPS and polyiso all have different pro's and con's.

Polyiso has the highest R-value per inch of thickness. XPS is better against deep cold, 1/2"-1" on the cold side of the main polyiso is the best combo.

Brand doesn't matter.

Most people look locally and get what's cheapest per R-value.