Relectix - Over or under insulation?

[Paisley777]

Hello,

I will be working on the walls this month.  I have been trying to read about reclectix and how it woks.  Interesting stuff.  One thing I read (I think on this page) is that it needs an airspace to work best.  That brings up a question.

I see installs like this all this time, with it right up against the metal :
http://lowgravityascents.com/2015/02/28/insulation-living-in-a-van-vanlife/



But I was wondering if this might be a better use of its properties because there is air space on both sides:
http://www.rimainternational.org/wp-content/uploads/2011/03/reflectix-3-large.jpg





Am I misunderstanding how this works?

Thanks all

 

[MrNoodly]

Reflectix is often used wrong. There needs to be an air barrier. UNLESS you're using it primarily for its ability to reflect light -- like people do when they make inserts for their windows. I built a box out of 2" foam to hold my refrigerator. I put Reflectix on the outside to reflect light coming in the windows. If I were to use Reflectix next to exterior walls, it would be to create an air barrier for some other type of insulation. Reflectix is essentially just shiny bubble wrap, after all. The space inside and between the bubbles is air space -- but only about an 1/8" of it.

 

[Almost There]

+1 on it being incorrectly installed in vans wrong A LOT!

Don't mistake installations in houses with how to use it in a van.

I used 5/8" bubble wrap glued to the reflectix on the side that was going to go against the van wall to create an air gap and so far I've been impressed with it. The combined panels were then taped with metal tape to the upright supports.Because the interior walls are fastened to strapping, there is also a dead air space between the reflectix and the interior walls.





This winter will be the true test as to whether I need to take the wall panels off and add some polyiso insulation as well.

 

[accrete]

: ) What he said...

And, for our build we used a sandwich.
I started on the inside of the van wall with the largest packing-bubble wrap I could find. It ended up being about 1" thick bubbles. This was glued to the inside of the painted metal with 3M 77 adhesive. Then we put Reflectix on that, then another layer of 1" bubble wrap. Another Reflectix, this is what you would have seen just prior to our gluing the marine grade hull fabric over it all.

The build is five years old this October and I purposely went down to metal I a couple areas to check the adhesion at this point down the road. In those areas all was as it was at time of build. It shows no signs of age. Also, the sandwich works great as a sound deadener too. And it does do te trick for us as an insulation-sandwich. The funniest _test_ was waking up one morning, opening the slider to find it had snowed about 4" since we crawled into bed.

YMMV
Thom

 

[BradKW]

I just happened to watch this video last night...worth sharing:

 

[Almost There]

I just happened to watch this video last night...worth sharing:

Good explanation - that needs to be a sticky for all the future questions!

 

[Paisley777]

So, given the metal wall, the std insulation, & the paneling... does it really serve any purpose to add a radiant barrier?  If you do, then you have to make a real plan to have a gap between it and your next layer.  (like the bubble wrap idea)

 

[Paisley777]

Well heck, if I'd seen this before I wouldn't have had to ask in the first place.

http://www.cheaprvliving.com/blog/understanding-insulation-van/

 

[akrvbob]

Even done right by leaving an air gap, your money would be better spent by buying Polyiso sheet insulation. It's the best answer for insulating the walls. Most of the time you can find it with silver reflective material on one side so it is every bit as good as the Reflectix, but it is almost R-7 while the Reflectix is essentially R-0. Yes, they claim it is R-1, but there is no government or industry standard for R-values of REflective material, because they have none. They simply made up the number.

On the other hand, R-values for insulation are tested by the industry and the government and proven to be true.

The one time Reflectix in a wall is a very good choice is if you are only concerned about heat and not about cold. It does an excellent job of that if installed right.
Bob