Reflectix Experiment - Fiberglass RV
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Old 05-20-2015, 09:52 AM   #1
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Reflectix Experiment

I got a roll of reflectix and covered the 4 main windows and the roof vent in my Parkliner. The reflectix by itself doesn't seem to be enough.

I checked the temp inside the trailer and it is 85 degrees and the outside temp is only 80. The temp on the inside side of the reflectix is 85, the same as the inside trailer temp, which makes sense.

So where is the heat coming from? Some of it is coming from the metal window frames and metal vent frame. Both of these are over 110 degrees on the inside of the trailer. The window glass is also very hot.

I have a roll of duct insulation wrap which is fiberglass with a foil jacket. I think I might try using that on the edges of the reflectix to cover the metal frames. Any ideas on what else to try?
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Old 05-20-2015, 10:43 AM   #2
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measurements

I suspect you are using an IR thermometer. Keep in mind that when you point at and measure the temperature of a very shiny surface such as reflectix, you will be measuring the temp of everything but what you point at. If you really want to get an accurate measurement of the surface of the reflectix, stick a piece of black electrical tape on the reflectix, wait a few minutes and then measure the tape temperature.
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Old 05-20-2015, 11:05 AM   #3
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I look at it this way. Its about thermal mass. The trailer has huge surface area absorbing heat or loosing heat. You put in reflextic in the windows and vent on maybe 15% of the trailer surface area. The reflextic resists the heat transfer until it becomes neutral to its surrounding area. Once it becomes the same heat level it will no longer be an insulator but a resistor due to heat transfer. It will radiate the heat like everything else. Its sole benefit is it doesn't heat up or loose heat as fast as a more conductive surface like glass or metal. By the way was your reflextic double bubble or single bubble. My Scamp was built with double bubble. Foil face, bubble, bubble, foil face, sandwich. Most of the stuff I see commercially available these days is foil, bubble, foil.
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Old 05-20-2015, 11:07 AM   #4
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Only doing the windows and the roof vent won't stop the radiant heat throughout the rest of the trailer.

Reflectix used as a heat or cold block on the windows etc is handy to use when the rest of the vehicle/trailer is also well protected by either the radiant barrier provided by reflectix or by insulation.

Just doing the small area of windows and the vent won't do anything at all as you've seen by your tests.

BTW, if you do go to put a radiant heat barrier on the rest of the trailer, keep in mind that unless it's got an air space between it and the trailer wall/ceiling it will do absolutely nothing. I am using bubble wrap adhered to the reflectix as each panel is cut to do the inside of the van I'm working on...it works!! I can tell the difference and I'm only half finished.
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Old 05-20-2015, 11:20 AM   #5
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Putting the duct insulation on the metal frame of the roof vent seemed to help a little. I also closed all the curtains. I opened a window on the shady side of the trailer and turned the roof fan on medium blowing out. The outside temp is up to 83 and the inside temp is 86, so at least for this time interval, the outside temp is going up faster than the inside temp.

I had an awning installed last year, but haven't used it yet. I'm thinking that pulling air in from the awning side should help cool the trailer when it is parked directly in the sun.
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Old 05-20-2015, 12:15 PM   #6
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Originally Posted by Huck View Post
I'm thinking that pulling air in from the awning side should help cool the trailer when it is parked directly in the sun.
Yes it will. I have found that having the awning and the shade it provides can indeed help.
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Old 05-20-2015, 01:39 PM   #7
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Yes it will. I have found that having the awning and the shade it provides can indeed help.
I've also discovered that hanging wet (soaked) towels on the sun side of an awning or canopy actually cools the underneath area a bit. They provide shade from the setting sun and sitting near them is pleasant, especially if there is a breeze.

Not exactly upscale in appearance, but helpful temp-wise.

I kept a pan of water nearby and re-soaked them as they began to dry.

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Old 05-20-2015, 01:42 PM   #8
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BTW, I haven't been able to try this (being currently ISO), but I suspect a wet towel hanging over the open door, and possibly several others hanging inside with a small exhaust fan running would help the temp inside. Would love to hear a report from anyone who tries this.
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Old 05-20-2015, 02:04 PM   #9
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My first summer trip across the AZ-CA desert without AC involved exactly that: wet towels hanging in the open windows of my pickup. They were bone dry in 10-15 minutes!
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Old 05-20-2015, 03:33 PM   #10
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I can also share that when riding pillion in 100 degree plus weather (and wearing black armored gear) that it is quite acceptable to take off one's t-shirt (while stopped and dismounted of course), soak it in a nearby stream, and pour water over one's head.

The cooling effect lasts, like your towels in the desert, for about 10 minutes, but may delay heat stroke.

I've also discovered that it's cooler to sleep under a very damp sheet than it is to sleep completely uncovered. I actually think that several wet sheets strung this way and that in a warm FGRV with a breeze blowing through would significantly lower the temp.
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Old 05-20-2015, 04:20 PM   #11
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Originally Posted by starbrightsteve View Post
I suspect you are using an IR thermometer. Keep in mind that when you point at and measure the temperature of a very shiny surface such as reflectix, you will be measuring the temp of everything but what you point at. If you really want to get an accurate measurement of the surface of the reflectix, stick a piece of black electrical tape on the reflectix, wait a few minutes and then measure the tape temperature.
Steve
IR thermometers work really good at 72°F AIR TEMPERATURE. A few degrees away from that 72°C point the accuracy goes away rapidly. That's one of the big and I mean BIG problems with IR thermometers. It's very easy to make an IR thermometer that works great at room temperature. Going away from room temperature takes a whole lot of work. It took us, the engineers at company I retired from 4 years and about 1 million dollars to solve the varying air temperature issue.

NOT only is it inaccurate at non room temperature environments, it taks close to 1/2 hour to get repeatable readings when moving from one temperature environment to another. Faulty measuring instrument are bain of most experiments. By faulty there's a whole lot to take into consideration.
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Old 05-20-2015, 05:46 PM   #12
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Must be somebody out there making a device to calibrate IR thermometers?
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Old 05-20-2015, 06:59 PM   #13
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boiling water is 212°F (100°C) and ice water is 32°F (0°C) for testing.


(At considerable altitude, the boiling water is not accurate.)
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Old 05-20-2015, 07:46 PM   #14
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Must be somebody out there making a device to calibrate IR thermometers?
The name of the company is Mikron. They cost about $10,000 each.
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Old 05-20-2015, 07:54 PM   #15
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I forgot to mention "Emissivity". IR radiation varies from material to material.
As you should be able to see by now IR temperature measurements are quite complicated. They're based on the Black Body formula. If want to see how complex is go here.
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Old 05-20-2015, 07:58 PM   #16
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Originally Posted by Roger C H View Post
boiling water is 212°F (100°C) and ice water is 32°F (0°C) for testing.


(At considerable altitude, the boiling water is not accurate.)
These are approximate number for distilled water at sea level. The ice is ice water can be a lot colder than 32°F for one thing. These number are "transition" numbers where water changes from liquid to a solid or the other way around, and where water changes from liquid to a gas or the other way around. Do NOT confuse water vapor with steam.
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Old 07-13-2022, 01:48 PM   #17
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Yes it will. I have found that having the awning and the shade it provides can indeed help.
I'm in the Northern California valley and it is Very Hot right now. My trailer is safe, parked behind a locked gate and on a paved pad, but it is in the sun.

It was heating up to an intolerable temp inside, which prevented work inside past 10 am or even earlier. We have investigated several carport options, but have not settled on a solution yet.

Temporary solution is: 10 x 10 pop-up canopy. I have one I was going to donate because one of the legs is damaged. But we managed to get the leg extended (will probably never get it closed again), and set the canopy up. It was about 20 inches too short to have the frame clear the trailer roof.

I purchased 4 cinder blocks, stood them up vertically. Friend used masonry bit, drilled hole in each. Stood canopy legs on 4 blocks, bolted down to prevent flight.

Pros: Trailer significantly cooler. More chores accomplished inside later in the morning.

Cons: Because of MaxAir fan cover, I can't simply tow the trailer out from under. When ready to move, will need to unbolt the front legs and have two friends lift that end up by a foot so I can get the trailer out.
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