I *finally* get it: Reflectix or foil need an air gap

[Vanholio]

It finally sunk in for me why Reflectix and other foil insulation needs an air gap. I wasted time and money the way I did it. Maybe this post will help others avoid my error, without trying to parse the physics. http://www.vanholio.com/2016/05/reflectix-insulation-in-vans-done-right.html

Oh, and how many times did I read it needs an air gap online? Yet I saw all those nice conversion photos and videos that did the opposite. I believed what I saw. Like a sucker!

 

[WriterMs]

It's great to see someone admit to their own learning process. Lots of us do that on this forum.... which does help others. You do have a "fun" site with a definite point of view. I'll go explore other posts on there from time to time.

 

[Vanholio]

It's great to see someone admit to their own learning process. Lots of us do that on this forum.... which does help others. You do have a "fun" site with a definite point of view. I'll go explore other posts on there from time to time.

And in all honesty, I've only gotten as much "right" as I have because of the many, many shares on this forum and blog (yes, I've been lurking a while), the vandwellers subreddit, many other blogs, YouTube videos, etc. This woulda been much harder before the internet. Even vandwelling how-to books, if they existed 15-20 years ago, would have been insufficient because you wouldn't have gotten enough perspectives and variables for different situations. Gotta thank the hard work of Bob and the many other bloggers, posters, sharers out there.

 

[Almost There]

And in all honesty, I've only gotten as much "right" as I have because of the many, many shares on this forum and blog (yes, I've been lurking a while), the vandwellers subreddit, many other blogs, YouTube videos, etc. This woulda been much harder before the internet. Even vandwelling how-to books, if they existed 15-20 years ago, would have been insufficient because you wouldn't have gotten enough perspectives and variables for different situations. Gotta thank the hard work of Bob and the many other bloggers, posters, sharers out there.

Actually it wasn't that hard. 40 years ago when I bought my first van I was also introduced to other vanners. We all formed clubs, attended 'rallies' known as van meets, shared information and travelled all over the north american continent.

There were van meets virtually every weekend during the summer and lots of hall and house parties during the northern winter.

The annual north american wide van meet would have somewhere in the range of 4,000 vans in attendance (depending on where it was that year).

In addition to the sharing, there were van parts and customization shops in abundance. Getting parts was much easier then than it is now!

 

[CraigL]

Twenty years ago, very little was said about radiant barriers.

 

[Gigi]

Thank you! This really helped me to get it too. I am still in the planning process and in doing research, have seen some people do some really elaborate things with the Reflectix that made my think...wow, is that going to compromise it's effectiveness? Now, I know that answer.

 

[Cheli]

Ok I think I got it. So if I understand correctly, I do NOT need to add rigid foam between the Reflectix and paneling? Just attach the Reflectix to the van wall, a gap, then paneling?

Sounds easy, thanks!

 

[Bladeforger]

Then it would make perfect sense that putting a fabric cover over both sides of Reflectix would, perhaps, make it a tiny bit less effective but that it would not kill the whole radiantheat-reflection process because the material would be **touching** the foil... as long as there was still an air gap between the sandwiched Reflectix shade and the window. Right? Does anyone have experience with that?

(Because that foil look is ugly enough to be a total deal-killer as far as my other half is concerned.)

 

[AngryVanMan]

Anything touching, or attached to the side intended to radiate will drastically reduce the effectiveness. Even regular dust settling on radiant barriers installed in attics diminishes the effect over time, perhaps as much as 50%. The TVA tested barriers with black plastic and kraft paper draped over top (to simulate very heavy dust), and in those circumstances the radiant barrier failed to perform as insulation at all.

 

[highdesertranger]

you need an air gap between the van outer sheet metal and the reflectix for it to work. if you put the reflectix right up against the outer skin it does no good, it's a waste of time and money. imo drop the reflectix and use polysio. highdesertranger

 

[Tulsatraveler]

you need an air gap between the van outer sheet metal and the reflectix for it to work.  if you put the reflectix right up against the outer skin it does no good,  it's a waste of time and money.  imo drop the reflectix and use polysio.  highdesertranger

I thought i saw a "how to" from cousin bob that said 1/2 inch shims along wall, (I'm not going to run them end to end, but rather random so the air can circulate better) them plastic wrap attached to the shims ( I'm going to use the blue  plastic they usually put down on a concrete floor under a wood lament floor - Very good moisture barrier - don't know about the price - yet.) then a layer of  - what is it poly sci or something - that is so good.  Thinking now of leaving it like that - no wood covering, but once I get it up I may cave in and cover  it with wood laminate flooring (floor- walls and ceiling)  not sure I'll just wait and see.

 

[highdesertranger]

the air gap must be 100% sealed you do not want air circulation. air circulation defeats the purpose of the air gap. highdesertranger

 

[Almost There]

I thought i saw a "how to" from cousin bob that said 1/2 inch shims along wall, (I'm not going to run them end to end, but rather random so the air can circulate better) them plastic wrap attached to the shims ( I'm going to use the blue  plastic they usually put down on a concrete floor under a wood lament floor - Very good moisture barrier - don't know about the price - yet.) then a layer of  - what is it poly sci or something - that is so good.  Thinking now of leaving it like that - no wood covering, but once I get it up I may cave in and cover  it with wood laminate flooring (floor- walls and ceiling)  not sure I'll just wait and see.

Moisture barriers are usually a waste of time and money for a couple of reasons. The steel outer layer of the vehicle IS a moisture barrier from the outside. Unless it's absolutely totally sealed, including putting in barriers behind screws, electrical outlets/light fixtures, etc, etc, an incomplete vapor barrier does no good. Providing better air flow and minimizing moisture is IMO a better way to tackle any moisture problems that crop up. What one needs in a desert environment is entirely different than in the PNW.

Reflectix properly installed with a DEAD air gap between it and the vehicle wall (bubble wrap is a good dead air provider, use of aluminum tape, not duct tape, etc.) will provide a good radiant heat barrier for when you spend a lot of time in hotter climes.

Polyiso which is what I think you're thinking of 'poly sci', is an insulation that can provide insulation against heat and cold and help keep down heat loss in colder weather when you're using a heater.

Each has their own purpose.

What you do for a covering over the radiant heat barrier and/or insulation is entirely dependant on how finished you want your vehicle to look.

 

[akrvbob]

If you are mainly concerned about heat and don't care about cold, then Reflectx has some value in a wall. If you are mainly concerned with keeping the van warm, just forget the Reflectix and burn the money instead--it'll do you more good.
Bob

 

[TrainChaser]

Okay, okay, I understand that the Reflectix needs an airspace.  Got it.  But...... HOW do you provide that space?  TulsaTraveler said shims-- 1/2" strips of rigid foam stuck to the wall?  If so, why wrap plastic foam with plastic wrap?  

Would someone mind giving step-by-step instructions, using small words and short sentences?  Sorry, but my A.D.D. is engaged and I didn't get much sleep last night, either.

 

[Matlock]

Okay, okay, I understand that the Reflectix needs an airspace.  Got it.  But...... HOW do you provide that space?  

If you insist on using Reflectix then you need to build a framed house. A wood framed house. Then, as the Reflectix instruction state, just staple it to the underside of the roof rafters.

Short answer, Reflectix is a waist of time and money inside a vehicle. It's aluminum foil and bubble wrap.

Instead..... Buy 4x8x1" sheets of Polyiso at Lowe's or Home Depot. Cut to size with utility knife and glue to walls of vehicle. Or, glue furing strips that you have cut to length vertically spaced every 2' and then glue the polyiso foam board to them. Several examples of both horizontal and vertical wood furing strip installations in Google Image.

 

[Matlock]

Here's one example.



And another.

Just my 2 cents worth

 

[Almost There]

Okay, okay, I understand that the Reflectix needs an airspace.  Got it.  But...... HOW do you provide that space?  TulsaTraveler said shims-- 1/2" strips of rigid foam stuck to the wall?  If so, why wrap plastic foam with plastic wrap?  

Would someone mind giving step-by-step instructions, using small words and short sentences?  Sorry, but my A.D.D. is engaged and I didn't get much sleep last night, either.

If you insist on using Reflectix then you need to build a framed house. A wood framed house. Then, as the Reflectix instruction state, just staple it to the underside of the roof rafters.

 Short answer, Reflectix is a waist of time and money inside a vehicle. It's aluminum foil and bubble wrap.

Instead..... Buy 4x8x1" sheets of Polyiso at Lowe's or Home Depot. Cut to size with utility knife and glue to walls of vehicle. Or, glue furing strips that you have cut to length vertically spaced every 2' and then glue the polyiso foam board to them. Several examples of both horizontal and vertical wood furing strip installations in Google Image.

Matlock - I respectfully but adamantly disagree with your opinion that Reflectix is a waste of time and money. Also that it has it's use only in wood frame buildings.

To make such a statement is to discredit not only the product but to also do the readers here a disservice.

Reflectix, when used for what it is intended and properly installed IS a valuable product. It is used in a wide variety of building types.

I chose to use reflectix for it's radiant hear barrier properties. As such it works, and works well, for its' intended purpose. I neither wanted nor needed insulation. Had I wanted a high value of  insulation I would have chosen another product, probably poliso!

To Train Chaser:

I spent a considerable amount of time reading here:

 http://www.reflectixinc.com/

before choosing to use Reflectix in my van conversion. I read until I had a fairly good understanding of what the product could and could not do for me and also how it worked. I also read a lot of arguments for and against using the product but found that most in use failures were caused by blatant installation errors.

Since the website does not include instructions on how to install the product in a mobile application, I had to figure out how to achieve that on my own. The main things to be learned are that reflectix must have *DEAD air space* on the side of the radiant heating to be effective and it has limited R value depending on the installation.

I purchased the 48" wide roll of Reflectix because the measurement from floor to lengthwise structure beam on the van was approximately the same. I ended up having to use 5/8" bubble wrap because that was all I could obtain. A thicker one would have been slightly better but I wasn't able to find a source for it here in Canada. It was also only 24" wide. With the fiberglass high top a 100' roll was sufficient.

I cut each panel to just slightly oversize to fit between each rib and running from the top cross beam to the floor. Once the panel was trimmed to fit properly I laid it out with the outer side up (outer side being the side that would be closest to the van wall when installed). I used 3M Super 77 spray adhesive to attach the bubble wrap to the reflectix panel, trimming away the excess after the glue set.

I did each panel and then installed it one at a time working my way around the van. You can see some of the pictures of the work in my build thread

https://vanlivingforum.com/Thread-Building-Arabella

To create a dear air space, *very important* I used aluminum tape, taping completely around the panel including taping it to the floor of the van. Using long pieces on the straight areas and as small as necessary pieces on the curves, overlapping by at least an inch at every seam.

I also cut pieces to fit the windows and use them for blocking light in parking lots with excess security lighting and on very hot days to block the suns' heat when I'm parked.

I only got the body of the van done last year before heading out so this year the doors will get the same treatment.

Yes, there are spots that didn't get covered. The ribs for example. I wasn't aiming for 100%. I figured 95% reduction in radiant heating would be good enough and so far, I'm happy. No I don't live where the temps get to 100F by 10 AM. That's why I have wheels....

 

[JeriLynn]

It finally sunk in for me why Reflectix and other foil insulation needs an air gap. I wasted time and money the way I did it. Maybe this post will help others avoid my error, without trying to parse the physics. http://www.vanholio.com/2016/05/reflectix-insulation-in-vans-done-right.html

Oh, and how many times did I read it needs an air gap online? Yet I saw all those nice conversion photos and videos that did the opposite. I believed what I saw. Like a sucker!

When I clicked on link the language was not in English. I am in Japan sometimes ads are in Japanese but not blogs. Hmmmm?

 

[TrainChaser]

I just clicked the link, and it's in English. Maybe there is some kind of auto-translate due to location?