Reflectix vs Mylar

[SilentJim1980]

So, I know nothing of insulation other than what I've learned here (higher R value = more insulating properties).

I have a 2017 Chevrolet Express 3500 Passenger LT ExtendedV8, Flex Fuel, 6.0 Liter van (with the windows).
My question is this, instead of buying Reflectix, which is not that cheap (that I can find) because I need roughly 32 inches (W) x 50ft (L). Roughly enough to cover all of the side & back windows.

Could I buy Mylar sheets (blankets)? Can get 10 mylar thermal blankets for $15 that measure 87inches long x 63 inches wide, glue them to cardboard (I have enough broken down cardboard boxes to wallpaper a house)/foam/posterboard box pieces & cut them to the shape of the window, black felt/material on one side with mylar on the other (Bob showed this in a video with black felt/reflectix).

If anyone has or has had the same van I as do could you reply with where you purchased your reflectix & in what dimensions? If substituting reflectix for mylar isn't a good idea.

​

 

[WayOutWest]

I got my reflectix at Home Depot, it came in rolls, one size was 24 inches wide, the other size was 48 inches wide. I didn't think it was that expensive...you can probably search online and find the cost.

 

[BinDerSmokDat]

Another option is Traffic Master roll underlayment. Home Depot sells it for about $40 a rool. It is 4' wide and foil faced, the material itself is 0.080 polyethylene. I used it in my build over top of my expanded polystyrene (pink/blue board) because it was thin enough to go over all of the raised wall and ceiling ribs and still be able to panel over it. It also has self adhesive edges so I was able to overlap and seal the edges, basically cocooning my interior.
Added bonus, it works in the van the same way it does on floors to reduce rubbing/squeaking between polystyrene sheets or struts/ribs and your wall covering/paneling.

It is thin but thicker than the mylar and can be used throughout the build where you want more draft stopping and reflectivity.
At 4' wide you can trim off the unneeded self adhesive edge and still have enough width to get two window covers across the roll.

Also mylar is a pain to work with and no matter how careful you are with it the foil/reflective stuff always rubs/flakes off over time.

 

[BinDerSmokDat]

Update I just checked the piece I have left and I have the 0.093" thick stuff, that must be what my local HD sells.
the 0.093" is a little pricier than what I said, $58/roll.
I got the 0.080" thickness and $40 from HD online.

I would see no issues doubling or even tripling the 0.080" especially as a roll provides a ton of material and just shooting it with some spray adhesive between layers.

 

[bebewanna]

As I have been more concerned with blocking heat than staying warm... I don't know how all of the Mylar sheets work but the ones in the link did an amazing job in 118f weather, blocking hest... The long front windshield was cool in baking sun, covered with these ... You can find black backing ones also...

I am camped where stealth doesn't matter...

https://www.amazon.com/Altland-Emer...prefix=mylar+blankets+altland+,aps,948&sr=8-3

 

[maki2]

The only difference between a space blanket and refectix is the air bubbles layer. The reflective surfaces are created using the very process of applying a micro thin layer of aluminum onto a mylar plastic surface.

 

[Happy Camper]

In my apartment I have a large set of windows that gets hit by the sun. In the summer the heat radiating from the windows is crazy.

So a couple years ago I did research and decided to get some window film with a reflective coating to, well, reflect the sun rays and keep my place cooler. Ordered it on Amazon and since it wasn't prime, it took a couple weeks to get to me.

By that time summer had started early, and temps were in the 110 range constantly. So I thought hmm, since my stuff from Amazon isn't in yet, I'll run to the 99 cent store and buy some cheap foil. Did so and covered the windows and it was like I had turned a heater off. Worked so well that when the roll from Amazon came in, I returned it and left the foil on. Cost me $2.

Whether it's mylar, reflectix, or foil, what you're trying to do is reflect the sun's light away from your vehicle. It's as simple as that. Some people paint their roofs white to keep their interior cooler for this exact reason. Which solution you use is up to you.

That being said, make sure you're not blinding people with that reflected light. Especially if you're planning on driving with that reflective material in your windows.

 

[user 16179]

So, I know nothing of insulation other than what I've learned here (higher R value = more insulating properties).

I have a 2017 Chevrolet Express 3500 Passenger LT ExtendedV8, Flex Fuel, 6.0 Liter van (with the windows).
My question is this, instead of buying Reflectix, which is not that cheap (that I can find) because I need roughly 32 inches (W) x 50ft (L). Roughly enough to cover all of the side & back windows.

Could I buy Mylar sheets (blankets)? Can get 10 mylar thermal blankets for $15 that measure 87inches long x 63 inches wide, glue them to cardboard (I have enough broken down cardboard boxes to wallpaper a house)/foam/posterboard box pieces & cut them to the shape of the window, black felt/material on one side with mylar on the other (Bob showed this in a video with black felt/reflectix).

If anyone has or has had the same van I as do could you reply with where you purchased your reflectix & in what dimensions? If substituting reflectix for mylar isn't a good idea.

r​

According to the manufacture, Reflectix has an R value of 1. About the same a cardboard (corrugated, not beer boxes}. So it's main advantage is that it's water, condensation proof. It's so inexpensive for enough to do a minivan that there's no way I would mess with gluing anything to cardboard.

 

[Spaceman Spiff]

Cardboard is actually a good insulator (R-value = ~3.5). It is slightly better with the 'tubes' oriented horizontal in horizontal applications.
The claimed R-value = 1 of Reflectix is with a 3/4" air gap (3/4" of dead air, R-value = ~.6).

The measured R-value of Reflectix in a horizontal orientation with an air gap of 3/4" on both sides is ~1.7.
source: U.S. Department of Energy, DOE Handbook, table 5.1.3.

 

[maki2]

I am see that there is some confusion among responses as to how refectix or space blankets add benefits. R value in this case is basically an irrelevant measure for determining if it is a worthwhile product. It should not be compared to either ridgid foams or bats. Those slow down the transference of heat through the material, how effective they are at doing that is stated as R value.Reflective materials do not work that way.

What a reflective material does is redirect the heat back towards the source of the heat. It requires a mirror like surface to achieve that therefore the word reflection was used which became the product name Reflectix. in the case of keeping heat out of your vehicle a shiny surface faces the outside. For keeping warmer if you have an interior heat source the shiny side faces towards the heated interior.

As far as an understanding thermal control it is important to remember that heat moves towards the cold, that cold does not move towards the heat. Reflective materials redirect the heat towards the source. The higher R value products slow down the heat escaping towards the colder side. Of course a cold draft blowing in will drop the temperature. also you will feel colder next to a cold glass or metal surface. The air bubbles in Reflectix covering over a piece of window glass will at least help you there as the surface of the Reflectix will not feel as cold as the glass surface even in an unheated space should you be in physical contact with that surface.

Your most effective solution is to have some ridgid or batting insulation to slow down the heat transference as well as utilizing the heat reflective materials. Also get rid of drafts especially near your bed. But do have some fresh air coming in so your body stays oxygenated. My fresh air intake is not right next to my bed other than on warm nights when I open most of the windows.

My own personal window coverings has a layer of mylar bonded to a layer of EVA foam. That is available in the form of camping pads sold to put under your sleeping bag to reflect your body heat back at you from the mylar while the foam helps cusion you as well as slow down the heat transference. I flip them shiny side out facing the sunny side on hot days. At night in cold weather the shiny side faces in. It is pretty durable but clear packaging tape along the edges is a good idea as the edge of foam can tear into the piece with stress over time. The tape gets rid of that issue. So with care the window coverings will last you for a number of years. EVA foam can be painted if you want to make that side black or grey.

 

[Frood]

Reflectix in and of itself does kind of a poor job as an insulator. Where reflectix really shines is in blocking certain types of radiation that easily convert to thermal energy when absorbed by a material. Generally, if you are trying to keep the inside environment at a different temperature than the external ambient temperature, then you want to insulate. The bigger the desired temperature difference then the more efficient you want your insulation. The lower the efficiency of your insulation, then the more energy/fuel will be needed to maintain the desired temperature difference. To block heat, shiny side out, to retain heat, shiny side in... Bounce energy away to keep cool or keep it trapped inside to keep warm.
I highly recommend everybody learn about thermodynamics. It's an exceptionally fascinating subject and a branch of science that has an incredible amount of direct applications for what is learned.

 

[user 16179]

In my apartment I have a large set of windows that gets hit by the sun. In the summer the heat radiating from the windows is crazy.

So a couple years ago I did research and decided to get some window film with a reflective coating to, well, reflect the sun rays and keep my place cooler. Ordered it on Amazon and since it wasn't prime, it took a couple weeks to get to me.

By that time summer had started early, and temps were in the 110 range constantly. So I thought hmm, since my stuff from Amazon isn't in yet, I'll run to the 99 cent store and buy some cheap foil. Did so and covered the windows and it was like I had turned a heater off. Worked so well that when the roll from Amazon came in, I returned it and left the foil on. Cost me $2.

Whether it's mylar, reflectix, or foil, what you're trying to do is reflect the sun's light away from your vehicle. It's as simple as that. Some people paint their roofs white to keep their interior cooler for this exact reason. Which solution you use is up to you.

That being said, make sure you're not blinding people with that reflected light. Especially if you're planning on driving with that reflective material in your windows.

I had never thought about driving with my reflective covers in place. But the one in the windshield would sure be a big help on westbound evenings.

 

[Happy Camper]

Well, if they can't figure out that they shouldn't drive with the windshield cover, they won't know they are going the wrongway2.