Camper Thermal Engineering for Extreme Cold & High-Altitude: Arctic Antarctica Tibet

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OptimusPrime: My apologies. This "photo-esssay" of possible thermic solutions for very large windows in extreme cold climates is running a bit longer than I expected, and I had to sort of "go around you"...... I will respond to your post properly once I am done with this series, later on Sunday afternoon.


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11. Insulating the Front Windshield


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Now even if the front windshield has to be single-pane, the solution is fairly simple: for maximal insulation (as well as privacy), blinds would fold down to insulate the cab-area at the very front:





This is a photo of the pull-down blinds in the Concorde "Charisma" -- see http://www.concorde.eu/en/models/charisma-iii/description/ . For added insulation in extreme-cold climates (below -20 C), perhaps all of the windows of the camper should be equipped with “thermal blinds”.

The expression “thermal blinds” seems to be standard usage in the industry. But they are also called “thermal silver window screens” and “thermal window matts”. See for instance http://www.reimo.com/en/D-accessories_store/DU-windows_skylights/DUU-thermal_blinds/ , http://www.reimo.com/en/M37290-thermomatte_luxus_vw_t4/ , http://www.swcampers.co.uk/shop/ , http://www.reimo.com/en/M37240-isoflex_thermal_shield_mercedes_207_410_for_driver_s_cabin/ , http://www.swcampers.co.uk/product-category/thermal-silver-window-screens/ , http://www.campervanconversion.co.uk/van-window-insulation-mats , http://www.kiravans.co.uk/left-side-screens-vw-t5.html , http://www.kiravans.co.uk/campervan...s/thermal-silver-screens-for-camper-vans.html , http://www.leisureshopdirect.com/caravan/caravan_accessories/motorhome_thermal_screens.aspx , http://www.leisureshopdirect.com/ca...milenco_universal_internal_thermal_blind.aspx , http://www.rvworldstore.co.nz/universal-thermal-blind-set-for-motorhome-cabs , http://www.milenco.com/products/universal-thermal-blinds/ , and http://www.milenco.com/products/universal-thermal-blinds/universal-internal-thermal-blind/ .

In smaller and less expensive vehicles, these these thermal window matts are just fitted into place:






[video=youtube;xOtJy1a0V2I]https://www.youtube.com/watch?v=xOtJy1a0V2I [/video]


One of the more popular products of this kind seems is "Reflectix", or "reflective insulation" -- see http://www.reflectixinc.com , http://www.reflectixinc.com/basepage.asp?pageIndex=622 , and http://roadtreking.com/keeping-cool-in-rv-reflectix/ :


[video=youtube;Lb2GRIwttxI]https://www.youtube.com/watch?v=Lb2GRIwttxI [/video]
[video=youtube;FMKb4Tr3bUM]https://www.youtube.com/watch?v=FMKb4Tr3bUM [/video] [video=youtube;mxgq9IOJCrU]https://www.youtube.com/watch?v=mxgq9IOJCrU [/video]


But there are other products on the market, like "AtticFoil" -- see for instance http://www.atticfoil.com/applications-a-uses/exterior.html and http://www.atticfoil.com/products-2/attic-tent.html :


[video=youtube;1x-heDn9JQQ]https://www.youtube.com/watch?v=1x-heDn9JQQ [/video]


In a well-designed integrated motorhome, perhaps this kind of thermal insulation should be incorporated into retractable blinds, as pictured in the photo of the Concorde above?


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12. MCD Roller Shades


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Retractable thermal blinds could also be described as “thermal roller shades”. One of the more popular brands in the United States is MCD, which claims that it is the “leader in roller shade technology” for RV's – see http://mcdinnovations.com , http://mcdinnovations.com/index.php/american-duo , and http://mcdinnovations.com/index.php/installation-gallery . Here are some fairly detailed photographs of MCD roller shades installed at the front of a Prevost coach:








But perhaps in order for the thermal insulation to be really effective, it has to be much thicker than these MCD blinds? So a “thermal roller shade” solution like MCD probably will not work. It might be good for cutting out sunlight and heat gain, but not very good for retaining heat in very cold climates?


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13. Insulating the Front of the Vehicle Against Solar Gain: MCD Day Semi-Transparent Day-Shades


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However, here it is worth noting that MCD shades have two parts: the completely opaque “night shade”, and a semi-transparent “day shade”. Here is a window inside an RV, above a couch, with just the semi-transparent MCD “day shades” lowered:





Here is the window, with the opaque MCD night-shades partially lowered:





And here is the same window with the night-shades completely lowered:





Here is as similar sequence for the combination of MCD day-shades and night-shades in the cockpit:





So the semi-transparent “day shade” portion of the MCD product seems to make lots of sense.

Brief Disclaimer: please note that I am German, and so my design sensibilities tend to be European. So when I use photo examples of American products, please do not mistakenly imagine that I actually like the interior designs of American motorhomes. In most cases I do not. In fact, I very much dislike the interior designs of most American mainstream motorhomes, with only a few major exceptions, like Airstream or Newell Coaches. Airstream and Newell both know how to design interiors well.

So too, the interior designs of American expedition motorhomes are generally very good, for instance, those made by Earthroamer or Tiger. But for some reason, more mainstream American motorhomes by Fleetwood, Winnebago, etc., tend to have interiors best described as “grandma's kitchen”, or “colonial kitsch”. They are not Hymers, and they are not Concordes.....


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14. Protecting the Front of the Vehicle Against Solar Gain: Smart Glass


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One other possible way to reduce solar gain during the day might be the use of a recent innovation called “smart glass”, “switchable glass”, “privacy glass”, or “electrochromic glass” – see http://en.wikipedia.org/wiki/Smart_glass and http://www.youtube.com/playlist?list=PLEFCF7BA5FB5A3C1C . This idea is best illustrated with videos:


[video=youtube;7DbP0zqEVN4]http://www.youtube.com/watch?v=7DbP0zqEVN4&index=11&list=PLEFCF7BA5FB5A3C 1C[/video]


Honestly, I don't know if this will work. It probably won't work as well as Reflectix, the product already discussed above. Again, as a thermal specialist, campo, you would be in a much better position then me to say whether smart glass can help significantly in reducing solar gain.


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Now there are regulatory challenges facing the use of smart-glass in vehicles, because in many countries the front windshield especially cannot be tinted so as to reduce light transmission by more than 25 % -- see for instance https://www.gov.uk/tinted-vehicle-window-rules . So it is probably illegal in most countries to fit smart-glass film to the front windshield of a fully integrated motorhome. In many countries it may also be illegal to fit smart-glass film to the side windows of a car or motorhome.

But for the other windows in a motorhome, a smart-glass layer could replace the need for MCD-type roller blinds. Here are some videos about “smart film” fitted to the side windows and sunroofs of cars:


[video=youtube;ZiT9U7R809g]http://www.youtube.com/watch?v=ZiT9U7R809g&list=PL5E83ACA8B2587CEB&index= 2[/video] [video=youtube;itLqUDlw2tk]http://www.youtube.com/watch?v=itLqUDlw2tk&list=PL5E83ACA8B2587CEB&index= 4[/video]


Also see the Youtube Playlists at http://www.youtube.com/playlist?list=PLZcplsxGuxXl1059zkV2jFwozRqotYxHd and https://www.youtube.com/playlist?list=PLGClgtMl7AyhBhlKNu4dMBXfdwMmTaV7R .


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Here is what BMW did with smart-glass, in a car whose sunroof changes pattern:




What smart-glass cannot replace, however, is the need for additional thermal insulation. If the front and side “bonded” windows of an integrated motorhome are still single-pane glass, then adding a smart-film layer might only prevent solar gain.


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15. Thermal Curtains


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So perhaps the front windows need to be fitted with much thicker “thermal curtains”.





Or perhaps they need to be fitted with a “Thermo Separation Curtain”, like this one from Reimo:





See http://www.reimo.com/en/37318-thermo_separation_curtain_for_ducato_from_model_year_2007/ .


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16. Conclusion


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You get the picture: I am imagining a TerraLiner with lots of natural daylighting. As I wrote in post #104, for me lots of natural daylighting is a symbolic as well an aesthetic requirement:

....the light-filled “open-ness” of the VW Microbus seems to symbolize that it has nothing to hide; that it is curious about the world; and that it wants to “see” the world through as many windows as possible (no less than 23, in the Samba version). So for me, generous windowing is as much a symbolic, psychological, and almost "political" consideration, as it is an aesthetic one, a matter of designing an interior that will be filled with lots of natural daylight.

But I also understand how wanting so much window-surface, in a motorhome that is supposed to handle Arctic conditions, might seem a bit contradictory. I don't know if it can be done, or what is necessary to make it feasible. But if could be feasible, and the fuel-consumption that so much windowing might entail could be kept within acceptable limits, then this is what I would prefer to design.

Now the R-values for a bonded, curved, single-pane front window will be much worse than the R-values for the KCT windows. But this is true for all fully integrated motorhomes, as well as for van conversions. So the motorhome industry has come up with various solutions, as described above. Once again, perhaps the most elegant solution I've seen thus far are the blinds installed in the "Charisma" motorhome by Concorde:





I don't know the R-value of KCT windows, and could not find the information on their website. And of course the R-value of the windshield at the front of the motorhome will be anyone's guess. It will all depend on its thickness, the manufacturer, the glass technology used, etc…… This is very technical information, and it's probably not the kind of information that would be easily available on-line.

As things stand, however, you could probably do a pretty good rough-ballpark calculation for the TerraLiner using the following figures:


(1) Camper Box 9.5 m long, running from 1.6 m above grade to 3.95 m above grade, i.e. 2.35 m high.

(2) Double-pane or triple-pane windows: 10.83 m[SUP]2[/SUP]

(3) Single-pane front panoramic window: 5.5 m[SUP]2 [/SUP]

(4) Three skylights, double-pane or triple-pane, appox. 3.0 m[SUP]2[/SUP]


But as suggested above, all of these windows and skylights should be equipped with very effective "roller thermal shades", so that during the night they would be more effectively insulated against heat loss. And during the day, the same roller blinds and/or smart glass could render them opaque and resistant to solar gain.

In any case, I hope that the above thoughts help.

All best wishes,



Biotect

 

[campo]

Please Go On !!

 

[campo]

In between I allready give the results of my extra thermal calculations.
These concern my RV expedition truck MAN TGM as it is built today.
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The repartition of the thermal heating needs (=losses)
in the example of my expedition RV (at -30°C) are:
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walls 40%
exterior tanks and calorifier 29% (part is only temporary)
first heat up 20% (temporary)
ventilation 7%
windows (double thermic glass) 4%
hatches 3%
door 1%
Electrical -1%
2 persons on board -4%
Total heater need 100% = 6.908 Watt at -30°C
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When I use a better insulation on the walls (today 40mm) and do overall 60mm (k= 0,58W/m²K)
then I win 1.208 Watt on a total of 6.908 Watt needed or I will need 17% less heater capacity.
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When I go with the today vehicle to environments with outside temperatures of -40° instead of the in the example calculation -30°C then I will need an extra 810 Watt or 6.908+810=7.718 Watt
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I my personal opinion these differences are not big enough to adapt the chosen heaters and system layout.
There is enough reserve in the today system to cover this.

Campo

 

[biotect]

Hi Campo,

Thanks for those calculations! I am done for the night with the (very long) series of posts in which I work out the glazing requirements of my concept design, and discuss possible insulation solutions. Will resume finishing that series tomorrow morning (Monday, September 21st).

Just a few points that struck me:


1) Walls seem like a very potent area of heat loss: 40 %. It's interesting that going from 4 cm to 6 cm reduces heating needs 17 %. That's quite a bit, don't you think? Perhaps the doors do not have to be 6 cm thick, but it seems like a good idea if the walls are.....

2) Is your program able to calculate what the savings might be if you increased the thickness of the floor and roof even further? What would happen if the roof increased to 10 cm, and the floor to 14 cm, as per the Doleoni MAN KAT? Would you see significant savings?

3) Your windows (double thermic glass) account for only 4 % heat loss. What is their total surface in square meters on your camper?

In the integrated, "Liner Type" motorhome that I am imagining, with lots of big windows, this figure will certainly be much higher!! But it would also be interesting to do a calculation for triple-thermic glass. Many houses nowadays have triple-thermic glass, so it is in principle possible that a motorhome could have triple-thermic too. For all the windows except the one in the very front, i.e. the windshield.

4) Very interesting that two people inside your camper adds 4 %!!! I never would have thought that human bodies could generate so much heat.

5) It's also interesting that going from -30 C to -40 C does not increase the KW demand that much. Rouhgly 12 %.

6) Clearly wall thickness is not the only thing that's important; type of insulation also matters, right? Most expedition motorhome campers nowadays seem to be made out of "self supporting sandwich plate panels of fibre glass composite.... with polyurethane foam insulation, reinforces polyester." But I wonder: are better forms of insulation available? Have you heard of flexible Aerogels, for instance? See http://en.wikipedia.org/wiki/Aerogel or http://fr.wikipedia.org/wiki/Aérogel .


Last but not least: What is your primary language of communication? French? Dutch? German? If you let me know, then wherever possible I will try to provide links (for instance, for Wikipedia) to websites in your best language.

All best wishes,


Biotect

 

[campo]

Practical glass and hatches insulation values:
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The nice KCT solution has a very good reputation. Main reason is that it is one of the only ones offering such a product.
As you can already imagine I am not so impressed by the KCT window’s:
- Very pore glass insulation value (KCT announces Ug 1,3 W/m²K but we found out that the KCT double glass is probably more something like 3,0 W/m²K.
The window frame value Uf is not announced)
- Huege framework, almost 1/3 of the window surface
- High price
- Weight is high
- Integration of the rollo could be better
- High altitude solution is debatable
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Competitor for KCT today is Outbound in the Netherlands who offers better prices for similar products.
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Fiat OEM Ducato wind screen
Front wind screen Fiat Ducato (camping van RV):
isolation 5,71 W/m²K
lucent transmission 78,0 %
energy transmission 52,1 %
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Side screens OEM Fiat Ducato:
insulation 5,71 W/m²K
lucent transmission 83,8 %
energy transmission 86,2 %
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RV plexiglass Windows Seitz S4 and hatches Seitz (Acryl) double
insulation 2,4 W/m²K and 1,65 W/m²K with closed curtains
(so it is important to close them when cold or warm environment as by night)
lucent transmission 73,5 %
energy transmission 60,0 %
(laboratory values given by the producer and maybe a little optimistic ?)
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Double glazed windows GEBO Thermic Line :
(values from glass calculation program www.yourglass.com/configurator)
introduced values :
Exterior glass 6mm Planibel Dark grey
air gap 9 mm 100%
Interior glass 5 mm Planibel Clear
(you can introduce argon as gas for better results but double price)
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Results of the simulation Gebo double thermic glass:
Ug value : 3,0 W/m2°K according to EN 673
With mentioning the possibility for important improvement by closing the curtains.
Light transmission (Tv) 7 ... I do not know what that means
Total energy ABSORBTION 89% … strange absortion is not transmission
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Gebo low profile hatches 24mm (Flushline) similar to Lewmar used on boats.
I think you can use values for the GEBO hatches from acrylic simple glass 8mm Acryliques Gebo
with a coefficient of +/- 5,0 W/m²K. When you close the curtains it will be a lot better like 2,0 W/m²K

 

[campo]

Of course the insulation thickness walls, floor and roof are important.
The choice will always be a compromise.
Thick walls make less space available inside and less comfortable door, window and hatch opening.
There for my personal conclusion is to use 50mm for a standard all temperatures expedition vehicle.
Do not go thicker than 60mm for really extreme vehicles.
It is easy to compensate poor insulation by slightly more performant AC and heaters.
For the few days that you will turn them on…
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The roof is the most important part because of the sun penetration there is most difficult compensation with air conditioning
what consumes a lot more electrical energy than a gasoil (diesel) heater in winter

 

[campo]

Skylight is nice and usefull to get a comfortable interior.
But it is dramatic when the sun is shining and you have to get rid of the over temperature and solar load.
The AC system will then be consuming all your electrical energy

 

[campo]

Windows with double thermic glass (6/9/5mm).
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Total weight for the 4 units was 75 kg
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[campo]

And here you see the very flat hatches as they are used on sport boats
The 24mm stream line was more important for me than the insulation factor.
From the inside there is the combined moscito and darkness roller.
I did only want to choose between hatches that cannot easily be broken from outside.
No entrance through the roof !
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