My Conversion van.....conversion

[Almost There]

Hmm...what about JUST reflectix and then the polyiso?  The extra bubble wrap seems like overkill...but i don't know about these things.

If you're not going to bother using the bubble wrap then there is NO point in putting in reflectix. It does absolutely nothing if there is no dead air gap between it and the van wall. There is no other effective method to ensure the dead air gap that I know of.

It's actually quite easy to use the bubble wrap. Buy the 48" wide reflectix because it is a near perfect fit for the side walls of the van. Cut a section and trim it to fit between the ribs of the van. Once you've got it fitted nicely, lay it down with the van wall side up. Spray with a spray adhesive (I used 3M Super 77 from H/D). Lay pieces of bubble wrap out on the glued up reflectix and then trim away the excess. Install the assembled panel with metal tape sealing it all the way around. On to the next panel...

It's actually one of the easiest jobs encountered in doing a DIY conversion and it goes fast!!

 

[phillipaaron]

Hmm...what about JUST reflectix and then the polyiso?  The extra bubble wrap seems like overkill...but i don't know about these things.

This is the route I went reflectix -> foam. Reflectix is for a radiant barrier and in my eyes should not be considered insulation. If you add the extra layer of bubble wrap (which effectively creates an air gap) the R-Value of the reflectix will increase, however, a small amount.

 

[waverider1987]

What about...the foam insulation that has the aluminum on it already?

 

[phillipaaron]

I would face the aluminum side out and call it a day.

 

[Milk Hauler]

Nice Van! [emoji12]

Sent from my SCH-S968C using Tapatalk

 

[flying kurbmaster]

I would face the aluminum side out and call it a day.

I think the alluminium side should face the inside, that is my understanding, I could be wrong, that is how I did it on mine.

 

[phillipaaron]

I think the alluminium side should face the inside, that is my understanding, I could be wrong, that is how I did it on mine.

That's dependent on your environment and something I didn't ask of the OP. In cold climates face aluminum towards the inside so the heat is reflected back. And the opposite for hot climates.

 

[DimondColorCloud]

I too think the reflective side goes inside. Otherwise the heat from the sheet metal gets transferred directly to the reflective material in the insulation. The foam side acts as a barrier and keeps the reflective material much cooler.

Learned it from this video,

[video=youtube]

 

[masterplumber]

Well I don't know which is better, as I have no way to compare side by side. I used the polyiso only on the walls, and faced the foil side out. On the ceiling I had an extra 1/4'' and had some relectex, so I put that up first, then the polyiso. It seems to work well for me?

 

[phillipaaron]

I too think the reflective side goes inside. Otherwise the heat from the sheet metal gets transferred directly to the reflective material in the insulation. The foam side acts as a barrier and keeps the reflective material much cooler.

Learned it from this video,

Reflectix and similar types of products provide a radiant barrier by "reflecting" radiant heat away. They perform very poorly at transferring radiant heat and thus do not heat up like other materials. As stated at the reflectix website here: http://www.reflectixinc.com/basepage.asp?PageIndex=384#WhatisaRadiantBarrier?

Wikipedia: "Radiant barrier is a radiant heat reflective insulation material. Radiant barriers (also known as reflective insulation) are a type of thermal (heat) insulations that inhibits heat transfer by thermal radiation."

I translate that to mean the reflective surface reflects the heat away as it inhibits the transfer of radiant heat which is what you will get from the sheet metal heating up. Facing the shiny side away from the radiant heat would defeat the purpose of a radiant barrier. Furthermore, the installation direction of the reflective surface would be dependent on which direction you're trying to reflect the radiant heat. This would come down to hot or cold climate. Hot climate, you want to reflect any radiant heat away from the inside of the vehicle. In cold climates you want to reflect any heat back into the vehicle. For example, sun shades for your windshield have a shiny side that faces out of the vehicle to prevent the sun's radiant heat from entering the vehicle and keeping your vehicle cooler.


Here's the Reflectix FAQ page which provides more details about how it works: http://www.reflectixinc.com/basepage.asp?PageIndex=384

If I'm incorrect about something then someone please correct me. However, this is my conclusion through research as there seems to be a lot of confusion on the internet about Reflectix and radiant barriers.

 

[akrvbob]

No reflective material is of any value at all without an air gap between the foil and the heat source. That's true of the aluminum foil on polyiso just as much as it is for the Reflectix. On my trailer I left the aluminum foil facing into the trailer but left off the paneling. Because it is exposed it does give me some heat retention value and also makes the inside of the trailer brighter. I'm glad I did it that way.

If you put paneling over it, it has no heat-retntion value.
Bob

 

[flying kurbmaster]

it is interesting that you say that it has no value without an air space, you have to wonder why they bother putting the alluminium stuff on. The foam I used, is designed to be used on houses over whatever siding is on existing house I believe shiny side in against old siding, nailed to it, between strapping, then vinyl siding installed over, it has plastic on the other side. I assume as a vapor barrier next to the new vinyl siding
OP sorry for hijacking your thread

 

[Almost There]

it is interesting that you say that it has no value without an air space, you have to wonder why they bother putting the aluminum stuff on. The foam I used, is designed to be used on houses over whatever siding is on existing house I believe shiny side in against old siding, nailed to it, between strapping, then vinyl siding installed over, it has plastic on the other side. I assume as a vapor barrier next to the new vinyl siding
OP sorry for hijacking your thread

The most important thing I learned when I was studying up on the use of reflectix was that WHERE it is being used dictates HOW it should be used.

The closest comparison I could find on the Reflectix website was the instructions for use in steel buildings because they don't have a section on using it in vans...

I went directly to the Reflectix website and read everything I could on the subject. I highly recommend that approach!

 

[phillipaaron]

No reflective material is of any value at all without an air gap between the foil and the heat source.  That's true of the aluminum foil on polyiso just as much as it is for the Reflectix. On my trailer I left the aluminum foil facing into the trailer but left off the paneling. Because it is exposed it does give me some heat retention value and also makes the inside of the trailer brighter. I'm glad I did it that way.

If you put paneling over it, it has no heat-retntion value.
Bob

Are we speaking of the same thing? I'm speaking of radiant barrier and not insulation R-Value. I fail to understand how a reflective surface needs air to reflect, which is what I'm taking from your statement, which could be an incorrect understanding on my part. 

With insulation you obviously need an air gap as that's what helps facilitate the insulation. However, as a radiant barrier you wouldn't need an air gap. For example it's not uncommon in Texas to have a spray on radiant barrier in the attic, it's literally a silver like metallic paint that is sprayed directly onto the wood framing inside the attic. This obviously can't have an air gap as it's sprayed directly on.

Not trying to be a pain just to reach a scientific explanation to how it functions iin certain applications. As it could be used as a poor insulator or a radiant barrier.

I'm going to see if Reflectix customer service can shed some light on installation as radiation barrier vs insulation.

 

[phillipaaron]

Ok, I stand corrected. A little science research settles it. You need an air gap for a radiant barrier. Without an air gap there is no radiant heat. Without an air gap means the materials are touching. If they are touching than any heat transfer is conductive and not radiant.

Now I need to figure out why my home had a "spray on" radiant barrier. Snake oil?

 

[ArtW]

interesting

 

[akrvbob]

Snake oil. The difference between insulation and radiant barriers is almost universally misunderstood.

Reflectix works great in windows, so it must work great on the walls and on the floors too, right? Wrong. Radiant heat easily passes through a window both going in and going out after reflecting on the aluminum. Everywhere else it has to have an air gap.
Bob

 

[DannyB1954]

I believe reflectix was designed to lay on top of other insulation in an attic. It was to reflect the radiant heat coming from the roof. There is usually lots of space between the insulation and the roof. Reflectix does not have any meaningful R value. It does trap gas within it's bubbles, so it does work to stop air flow which would be convection heat transfer, but being one layer, it is not real effective for that.
When I did the insulation in my last house I put a layer of aluminium foil under the sheet rock to reflect back in the heat I used during winter. So I had aluminium on both the inside and outside.
My understanding is that being in direct contact with the sheet rock, it would transfer conduction energy, but being next to insulation, that energy would not go far, and being shiny it would still radiate the heat back in. Whether it worked through a placebo effect, or it really worked is unknown. I was at 4.000 feet on the western side of the Sierras, (near Twain Harte Ca), and heated a 2,000 Sq' house with a single pellet stove for just under $200 a month.
Kitchen aluminum foil doesn't cost a lot, so I would also put it behind paneling in a van just for the heck of it, (Shiny side facing in. One side of the foil is duller than the other).

 

[waverider1987]

Maybe could have reflectix on both sides of pink foam board? Or is that overkill? Again I'm trying to cover all climates.

 

[phillipaaron]

Maybe could have reflectix on both sides of pink foam board?  Or is that overkill?  Again I'm trying to cover all climates.

To cover all climates that would make sense. You'll always face the shiny side in the direction you want the heat to bounce back towards. In summer you want to bounce the heat away from the inside. So, you want a shiny side facing outside. In the winter you want the heat inside, to bounce back into the vehicle so you want a shiny side facing inside. Just make sure you have that air gap or you're not going to have anything bounce back. That heat will just transfer to other material in the van via conductive transfer. So perhaps like this:

Van wall -> Bubble wrap -> Reflectix (double sided)-> Bubble wrap -> polyiso -> wall finishing

or perhaps the more thorough approach as you suggested:
Van wall -> Bubble wrap -> Reflectix (double sided) -> polyiso -> Reflectix (double sided) -> Bubble wrap -> wall finishing