[MsNomer]

For most people, windows are a minor portion of their "envelope." For me, they are essentially the entire mid-height section. Not only are the windows themselves maximum size all around, but there is no "box" around them, as many have, so the entire recessed area is either glass, aluminum or bare steel.

Several years ago, I made coverings for the side windows from a cheap Walmart quilt with the fake glued-together "stitches." The primary use has been for blocking unavoidable bright lights at night. I decided that this year's winter project will be to upgrade them, but I like the look of the existing ones so well, I decided to improve them rather than start from scratch.

The windshield screen doubles as a barrier between cab and rear.

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I have been using an identical one across the rear, but decided to upgrade to a quilt one. It wraps under the mattress and connects with the side curtain to insulate the living space not just from the rear windows, but from the entire rear area including the D-pillars. This is its first mock-up.

As you can see in the photograph, this quilt fabric is not blocking light very well, so I decided to add light-blocking fabric. As soon as the clerk handed me the folded fabric, I knew I could not use it on the rear curtain—its weight would pull the curtain off its magnets. It will work for the side curtains because they hang on hooks. For the rear, I bought the Class A sized version of the windshield cover and will attach the fabric with the shiny side out.

Sooo, I have three scenarios to test and compare if the cold weather lingers around long enough—quilt alone, quilt with heavy impervious white backing, and quilt with thin but reflective backing.

I have already determined that I can have at least a 25° differential across the original. (HF laser gun, surfaces taped per Gary's suggestion.) Given that I can practically see through it and a large percentage of its surface area is squished flat, this surprises me. Reflecting on the concurrent discussion of the R-value difference between Thinsulate and Polyiso, I wonder if the R-value of this fabric can even be measured. However, we both notice the substantial rush of cold air when it is removed.

More tomorrow, I hope. Any suggestions, @GaryBIS?

 

[Lolaeliz]

I love all of your windows. They make your van feel so big. I wish I had more windows. And your covers look great!! I had my window covers in and they kept my van cold when the temps outside warmed! So I took them out, figuring the sun warming was more effective than the "insulation" insulating. But my van is winterized and parked in the driveway until spring. So really I guess it doesn't matter. Maybe if I had reversed them, with the dark fabric and havelock against the window and the refectix facing in, they would have been better for winter mode.

 

[MsNomer]

Other than blocking the occasional light, the primary use of the covers is to keep the van from heating up in summer when we leave it at a sunny trailhead. It will be interesting then to see which works better—white or reflective.

 

[GaryBIS]

For most people, windows are a minor portion of their "envelope." For me, they are essentially the entire mid-height section. Not only are the windows themselves maximum size all around, but there is no "box" around them, as many have, so the entire recessed area is either glass, aluminum or bare steel.

Several years ago, I made coverings for the side windows from a cheap Walmart quilt with the fake glued-together "stitches." The primary use has been for blocking unavoidable bright lights at night. I decided that this year's winter project will be to upgrade them, but I like the look of the existing ones so well, I decided to improve them rather than start from scratch.

View attachment 82179

View attachment 82180

The windshield screen doubles as a barrier between cab and rear.

Amazon.com: EcoNour Car Windshield Sun Shade with Storage Pouch | Durable 240T Material Car Sun Visor for UV Rays and Sun Heat Protection | Car Interior Accessories for Sun Heat | X-Large (75 inches x 37 inches) : Automotive

Buy EcoNour Car Windshield Sun Shade with Storage Pouch | Durable 240T Material Car Sun Visor for UV Rays and Sun Heat Protection | Car Interior Accessories for Sun Heat | X-Large (75 inches x 37 inches): Windshield Sunshades - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I have been using an identical one across the rear, but decided to upgrade to a quilt one. It wraps under the mattress and connects with the side curtain to insulate the living space not just from the rear windows, but from the entire rear area including the D-pillars. This is its first mock-up.

View attachment 82181

As you can see in the photograph, this quilt fabric is not blocking light very well, so I decided to add light-blocking fabric. As soon as the clerk handed me the folded fabric, I knew I could not use it on the rear curtain—its weight would pull the curtain off its magnets. It will work for the side curtains because they hang on hooks. For the rear, I bought the Class A sized version of the windshield cover and will attach the fabric with the shiny side out.

Sooo, I have three scenarios to test and compare if the cold weather lingers around long enough—quilt alone, quilt with heavy impervious white backing, and quilt with thin but reflective backing.

I have already determined that I can have at least a 25° differential across the original. (HF laser gun, surfaces taped per Gary's suggestion.) Given that I can practically see through it and a large percentage of its surface area is squished flat, this surprises me. Reflecting on the concurrent discussion of the R-value difference between Thinsulate and Polyiso, I wonder if the R-value of this fabric can even be measured. However, we both notice the substantial rush of cold air when it is removed.

More tomorrow, I hope. Any suggestions, @GaryBIS?

Hi MSNomer,
I love my windows too!

I like the connecting the back and side curtains together and limiting the amount of air that can circulate behind the curtain and into the van interior.

You can get a rough estimate of the R value of the curtains if you know the inside air temp a few inches inside the shade taken with a regular thermometer and the surface temperature of the inside of the shade taken with the IR temp gauge. Use the blue painters tape on the inside surface of the shade to make sure its emissivity is about 0.95, which is what the IR temp gauge assumes.
Also good to do the test at night to eliminate sun effects.

The two shades I tested were pretty close in R value at about R3 to R4 - compared to R1 for single glazed window.
Actually quite good I'm guessing yours will be in the same ballpark.

Gary

 

[MsNomer]

Uh, Oh. Blue painter's tape is nowhere on my premises. Will green do?

 

[GaryBIS]

Uh, Oh. Blue painter's tape is nowhere on my premises. Will green do?

I think so.
It would be good to have the green tape everywhere you take an IR temp gauge reading. That way, even if its emissivity is not exactly 0.95, the error (small I think) will be the same for all readings and differences between readings on different surfaces will be good.

Gary

 

[MsNomer]

it's all set up. Temperatures are pretty stable right now throughout the van at ambient mid-50's. Thermostat for electric heater (situated under seat near batteries) is set to come on at 50°. Low tonight about freezing. I will measure in the morning before sun is an issue.

Tomorrow night may be better at mid-20’s, plus we will be sleeping in it, so inside will be warmer and I can take night-time measurement.

 

[Ken Allan]

I was in a Michaels craft store recently and saw rolls of Fairfield Solarize. This is a thermal barrier (hot or cold) fabric that's 50% aluminum, 50% polyester. Thin and flexible and not crinkly. Looks to be light blocking and would be easy to sew. I may have to try some quilted rear window curtains with a layer of Solarize. Possibly it would function like refectix but would be more foldable and easy to store.??
Solarize Liner Fabric - Fairfield World

 

[83Grumman]

Maybe they could make windshield insulator/curtains the same way but with a curve. Inflate it and stuff it against the windshield, one side dark one side light.

View attachment 82175


View attachment 82178

 

[MsNomer]

I suspect that Solarize is similar to Insulbright by The Warm Company.

Results:

Ambient: 24° (Colder than I expected)
Van Interior: 68° (Warmer than I expected)

Quilt Alone: 62° inside surface, 61.5° outside surface

Quilt with white light-blocking fabric: 64.5° inside surface, 51° outside surface

Quilt with thin reflective fabric: 64° inside surface, 40.5° outside surface


I will repeat tomorrow.

 

[RV8R]

I am no where near needing this for our build yet, but I will ride on your “curtain tails” when it comes time for;

1) Window Coverings

2) Thermal Curtains for closing off the cab to the living area (I know we have factory swivels on our 2021, but still think at night we will be closing off the cab with draw curtains for privacy, light & heat/sound.

I will follow your “thread” with much interest in performance test results & your conclusions.

 

[MsNomer]

I will leave the technical conclusions to garybis. My non-technical conclusion is that the van was warmer than it would have been and dark as a cave. I could hardly wait to let the light in.

 

[larry barello]

@GaryBIS , I'm curious. I have Arctic Tern double pane windows which seem pretty insulating. They are the last surface to show condensation in cold temps. They also have light blocking reflective shades. How would I go about addressing that systems thermal performance?

blue/black tape on the outside surface of the window and the inside of the shade + ambient temperatures? Measure the Delta t of the stack?

 

[Lolaeliz]

Maybe they could make windshield insulator/curtains the same way but with a curve. Inflate it and stuff it against the windshield, one side dark one side light.

I made mine and they fold up nicely. By stitching vertical lines every 7" or so they fold accordion style and fit nicely in the pizza oven shelf. I made channels and threaded 1/8" metal dowel rods through them at the first and last stitch lines, and the visors also hold them in place. (On all the other windows Neodymium magnets hold them up.)

These are one layer of Reflectix, and a layer of Fleece that's spray glued to the reflectix to make for easy sewing.

Not sure the blowup ones would work, as the air would heat up and cool down, depending on the temp, and either burst or fall off the window.

 

[GaryBIS]

@GaryBIS , I'm curious. I have Arctic Tern double pane windows which seem pretty insulating. They are the last surface to show condensation in cold temps. They also have light blocking reflective shades. How would I go about addressing that systems thermal performance?

blue/black tape on the outside surface of the window and the inside of the shade + ambient temperatures? Measure the Delta t of the stack?

Hi Larry,
This is the way I do it - its rough, but gives and idea. Probably better for comparisons of the different kinds of windows in your van than for absolute numbers.
The section in bold below skips over the BS and gives a pretty usable procedure.

If you look at the total stackup of materials to get an total R value, it might go something like:
Outside air layer R 0.35
Glass R0
Shade R value TBD
Inside air layer R 0.65
You want to get the TBD shade R value

You have these measured temperatures to work with:
Toutside
Tinside surface of glazing or curtain (taken with IR temp gun)
TinsideAir

The heat transfer equation is:
Qtotal = Heat Transferred = (TinsideAir - Toutside) (Area) / Rtotal

You don't have enough info from above to calculate the Rtotal (which would tell you how good the window/curtain is).

But, you can use a rough trick to estimate the total heat transfer, and then use that to work backward to Rtotal.
The trick is that you can estimate the heat flow (Qtotal) using the R value of the inside air layer and the temps on either side of it.
Qtotal = (TinsideAir - Tcurtain) (1 sqft) / (R0.65)

For example, say
Toutside = 29F
Tcurtain = 63F
Tinsideair = 70F

Qtotal = (70F-63F) (1sqft) / (R0.65) = 10.8 BTU/sqft-F (using the air layer inside the curtain)

Then, get the total R value of the full stackup using the Qtotal just calced:
Rtotal = (Tinsideair - Toutside) / (Qtotal) = (70F - 29F) / (10.8 BTU/sqft-F) = R3.8

This example is what I got for my single glazed van window with a Eurocamper multilayer shade mounted on it.
To say that this is approximate is probably being optimistic, but I have used it on both my van and house windows and the answers are reasonable. Probably better for comparisons rather than absolute R values.

------------
A simpler and maybe more accurate method is to pick a cold, calm night (no sun) and take 1) outside temperature, 2) inside glass or surface temperature, and3) the inside air temperature a few inches inside the glazing or curtain.

Then the heat loss out the glazing or curtain is directly proportional to the difference in temperature between the inside air temp and the curtain or glazing surface temp. That is, the warmer the inside surface temp, the better job the glazing or curtain is doing. If you get a difference of 20F with your single glazed glass window (maybe the back window or windshield) and with your double glazed window with curtain the difference is 10F, then your double glazing and curtain cutting the heat loss in half - I suspect you will find it even better than that.

Tips:

• Use painters tape where you take measurements with an IR temp gun (this is to get an emissivity close to the 0.95 that most assume)
• Use an accurate thermometer.
• Pick a cold calm night (this eliminates sun which can make it impossible to get usable readings, eliminates wind effect on outer air layer R value, and the cold makes the temp differences larger and easier to measure).
• Try to do it all over a fairly short time interval so things don't change.
• Take separate inside air measurements for each window that are inside that window and separated from the window by the same amount.

In the end, what you get is just an estimate, but its fun
Please let us know how the double glazed windows do.

Gary

 

[larry barello]

I did a quicky. I turned on the heater (webasto) and let the van sit for 2 hours to reach equilibrium (hah!) My I/R gun (HF) is crap. I use it for the pizza oven and tend to leave it out in the weather. I now understand using blue tape to measure the surface temperature, NOT the reflected temperature of a low-e surface! So, in very rough terms since I had to guestimate a bunch of stuff - mainly correcting the I/R sensor +6. Ambient was measured with aquarium thermometers - within a 1 C error band and a third sensor (meat thermometer), so probably ok.

Ta-out 40 (ambient)
Tg-out 40 (outside of glazing)
Tg-in 55 (inside glazing)
Ts-in 61 (inside, shade down - probably didn't wait long enough)
Ta-in 67 (not measured in proximity of the other measurements so bogus)

I measured a bunch of other places on the van and insulated panels were in the 61 range so with a first order approximation, the windows are doing as well as 1.6" Thinsulate and paneling. The cab area (OEM) was a few degrees cooler. Of course, the big heat sink is the cab windows which were not covered

I should have pulled out the I/R camera and taken some pictures. That would have shown the differences! Maybe tomorrow morning crank the webasto on high and wait a couple hours to get the interior into the 75-80 range to accentuate the difference (and get a new I/R thermometer)

I'm gonna repeat this tomorrow and check the windshield as a reference and take some thermal images as well (after visiting HD or HF for a new I/R thermometer.

Fun stuff!

P.S. rather than thermometers for ambient, how about a square of black paper suspended near the window and then use the I/R gun? That should be accurate and a lot faster, right?

 

[Dennis CampMaker]

On my current van build I had to create deeper window sills and this allowed me to also create solid window covers out of 1/4 plywood, 1/2 inch polyiso foam, 1/8 closed cell foam and fabric. My guess is they are about R7. I'll try Gary's method and see what R values I come up with.

 

[GaryBIS]

I did a quicky. I turned on the heater (webasto) and let the van sit for 2 hours to reach equilibrium (hah!) My I/R gun (HF) is crap. I use it for the pizza oven and tend to leave it out in the weather. I now understand using blue tape to measure the surface temperature, NOT the reflected temperature of a low-e surface! So, in very rough terms since I had to guestimate a bunch of stuff - mainly correcting the I/R sensor +6. Ambient was measured with aquarium thermometers - within a 1 C error band and a third sensor (meat thermometer), so probably ok.

Ta-out 40 (ambient)
Tg-out 40 (outside of glazing)
Tg-in 55 (inside glazing)
Ts-in 61 (inside, shade down - probably didn't wait long enough)
Ta-in 67 (not measured in proximity of the other measurements so bogus)

I measured a bunch of other places on the van and insulated panels were in the 61 range so with a first order approximation, the windows are doing as well as 1.6" Thinsulate and paneling. The cab area (OEM) was a few degrees cooler. Of course, the big heat sink is the cab windows which were not covered

I should have pulled out the I/R camera and taken some pictures. That would have shown the differences! Maybe tomorrow morning crank the webasto on high and wait a couple hours to get the interior into the 75-80 range to accentuate the difference (and get a new I/R thermometer)

I'm gonna repeat this tomorrow and check the windshield as a reference and take some thermal images as well (after visiting HD or HF for a new I/R thermometer.

Fun stuff!

P.S. rather than thermometers for ambient, how about a square of black paper suspended near the window and then use the I/R gun? That should be accurate and a lot faster, right?

Nice.

The IR camera is good for this, but be sure to use the painters tape in a few places in the picture. If on the IR picture, the painters tape is not the same color as the material its on, it means the material has a different emissivity than 0.95, and the temperature the IR camera shows for that material will be wrong. A lot of materials (nicely) do have emissivities close to 0.95, but some materials (eg bare metals) are way different and you either have to use the painters tape or adjust the emissivity (if the camera allows), or get bad temperatures.

If the IR camera software allows you to place tags with the actual temp at that location is helpful also.

But, if the IR camera shows a warmer temp in one area vs another than the warmer area is losing less heat - it does really show up well on IR pics.

I've heard of the idea of waving a piece of paper around in the air until its at the air temp, and then using the IR gun on it. Seems like it should work, but I've never tested the accuracy. If you wave the paper around to get it to the air temp it might effect the R value of the still air layer and then the curtain surface temp, so, give it a little while to settle down I guess.

One thing on your quick run is that the outside glazing surface temp being the same as the air temp raises a flag - the glass surface should be warmer as there is the R value of the stillish air next to the glass. Maybe try a couple times or a couple places if this happens. If there is wind, the glazing and air temps will be closer.

Gary

 

[GaryBIS]

On my current van build I had to create deeper window sills and this allowed me to also create solid window covers out of 1/4 plywood, 1/2 inch polyiso foam, 1/8 closed cell foam and fabric. My guess is they are about R7. I'll try Gary's method and see what I come up with. View attachment 82239
View attachment 82237
View attachment 82238

Really like those window frames!
Functional and aesthetic.

Gary

 

[MsNomer]

Well, so much for repeat measurements this morning. It was so dark we slept through sunrise. 🙄

I think if I didn’t have windows, I would need a bigger van.

@GaryBIS, what's your take on my initial numbers? If they don’t look right, what should I do differently?