Has anyone heard or used this product on the roof of a caravan or motor home ?
They claim reduces temperatures by up to 45%
converts rust and increases metal life
reduces roof maintenance by up to 80%
I can be contacted on togo4950@gmail.com if any one can find further information
mezza56 said
06:50 PM Apr 4, 2018
If you find out anymore info pass it on here on the forum mate
Bagmaker said
09:21 PM Apr 4, 2018
just cover the roof in solar panels. Shimples
IAN zzz said
09:52 PM Apr 4, 2018
hahaha ...
Bagmaker must be spying on me :)
Stay safe
ramblegambol said
07:51 AM Apr 5, 2018
I painted the roof of my motorhome with this 3 years ago. before I put on extra solar panels. Don't know about 45%, but it does make a significant difference. Easy to use with brush or roller, fairly thick stuff so does a great job of sealing up minor blemishes. One proviso, buy more than you think you'll need, as it doesn't go as far as they say- but 2x 5litre tins gave me 3 coats on my 6m motorhome. I reckon it's good stuff!
El Gringo said
10:24 AM Apr 5, 2018
john tog wrote:
Has anyone heard or used this product on the roof of a caravan or motor home ? Yes on my 11mt bus
They claim reduces temperatures by up to 45% Does reduce temp, but not that much in practice - you can definitely notice the difference though.
converts rust and increases metal life Does NOT convert rust, it's just an acrylic emulsion with ceramic micro balls, not a rust converter. Any paint prolongs metal life.
reduces roof maintenance by up to 80% Compared to what?
If your existing paint is loose or flaking you will need to prepare it very well.
I completely bare metaled my roof, then etch primed it, then 2 very thick coats of Thermoshield (30lts sprayed on with an airless gun) then 2 coats of Weathershield Gloss (same application).
If you don't top coat the Thermoshield with something it will yellow and powder off.
I actually mixed my Weathershield with Bondcrete, a trick I learned doing roof restorations many years ago.
-- Edited by El Gringo on Thursday 5th of April 2018 05:19:15 PM
robol said
05:11 PM Apr 5, 2018
I used THERMALATE, which is in a crystalline form. I mixed this ( app. 1.5 bags ) in with the two pack paint and applied it by roller, two or three coats. I left the sides above gutter line smooth and ran a line of masking tape along the edge of the curve. This looks better and is easier to keep clean. I also covered as much of the roof with solar panels as possible and left enough room underneath them to clean the roof.
I am not sure if it's the Thermalate or the solar panels but I am happy so far.
Worth the effort.
hako said
06:34 PM Apr 5, 2018
Solar panels actually make the roof of the caravan hotter, not cooler - the backside of a PV solar panel is typically about 30C hotter than ambient, assuming 0.8 kW/m^2 irradiance.
Thanks for the feedback i shall try the application when we get two days of fine weather in a row
yobarr said
10:05 AM Apr 6, 2018
hako wrote:
Solar panels actually make the roof of the caravan hotter, not cooler - the backside of a PV solar panel is typically about 30C hotter than ambient, assuming 0.8 kW/m^2 irradiance.
Rubbish......Solar panels on the roof of a house,with around 150mm clearance to allow air to circulate,will keep that house up to 38% cooler than if the sun shines straight onto the roof.Fact.We all know that panels run about 25 degrees hotter than ambient.I have 1520 watts of Solar on my van to run my 2.5kw AC,which I rarely have to use because of the panels keeping the sun off the roof.Think about it.....hot air rises,and with a van under 6 metres long,there is not much roof uncovered. Safe,and cool,travels. Cheers.
-- Edited by yobarr on Friday 6th of April 2018 10:11:30 AM
robol said
11:05 AM Apr 6, 2018
I agree with yobarr. I have around 100mm. from bus roof to underside of panel, this allows enough room to slide a soft broom under for cleaning the roof and gives plenty of ventilation for the panels. I mounted the panels on the same extrusion as they use on domestic applications. The panels work better if you can keep them a bit cooler.
Jaahn said
05:06 PM Apr 6, 2018
El Gringo
------then 2 very thick coats of Thermoshield (30lts sprayed on with an airless gun) then 2 coats of Weathershield Gloss (same application).
If you don't top coat the Thermoshield with something it will yellow and powder off.
-------
-- Edited by El Gringo on Thursday 5th of April 2018 05:19:15 PM
Hi El Gringo et al
As I understand the theory of Thermoshield, it relies on the surface properties of the 'special' paint to achieve the reduction in roof temperature. So if you over coat it with a normal paint that will not work. The micro spheres etc and the thickness has just a minor effect to make the temperature lower. I would say do not do it like that IMHO.
I have researched it a bit and have not been convinced it is better than pure white roof paint. Being much more expensive it may not be worth it. The comparison results claimed are made often, as usual, by comparing apples with oranges. As El Gringo said it has no other magic properties that will make the roof better than new.
Jaahn
El Gringo said
05:15 PM Apr 6, 2018
Jaahn wrote:
El Gringo
------then 2 very thick coats of Thermoshield (30lts sprayed on with an airless gun) then 2 coats of Weathershield Gloss (same application).
If you don't top coat the Thermoshield with something it will yellow and powder off.
-------
-- Edited by El Gringo on Thursday 5th of April 2018 05:19:15 PM
Hi El Gringo et al
As I understand the theory of Thermoshield, it relies on the surface properties of the 'special' paint to achieve the reduction in roof temperature. So if you over coat it with a normal paint that will not work. The micro spheres etc and the thickness has just a minor effect to make the temperature lower. I would say do not do it like that IMHO.
I have researched it a bit and have not been convinced it is better than pure white roof paint. Being much more expensive it may not be worth it. The comparison results claimed are made often, as usual, by comparing apples with oranges. As El Gringo said it has no other magic properties that will make the roof better than new.
Jaahn
Yes they go on a bit on the website about the surface properties, but as you said it's virtually the same as any white paint.
The thermal properties are the ceramic microballs mixed into the paint, this is the only advantage over any other white paint, and surprisingly they do actually work - and perhaps not surprisingly they work better the more (thicker) you put on.
As far as overpainting affecting it, well they even offer a clear coat to help prevent the discolouring and oxidising of the paint themselves.
So for me (and I am a painter by trade) I have the benefit of the insulating paint and the benefit of the glossy white Weathershield on top - 3 years now and going very well.
Cheers,
hako said
09:53 PM Apr 6, 2018
Yobarr and robol - you are both correct and I agree that solar panels can reduce roof temperatures. My apologies for making an incorrect assumption.
Regards
Craig1 said
10:10 PM Apr 6, 2018
Bloody hell Denis, you have lowered the tone of this forum! You , admit you are wrong and then apologies. keep up the good work and may it be 30.10 and rising in your world.
cheers Craig
yobarr said
07:25 AM Apr 7, 2018
hako wrote:
Yobarr and robol - you are both correct and I agree that solar panels can reduce roof temperatures. My apologies for making an incorrect assumption.
Regards
Hi Denis....All is good and this shows how easy it is to draw incorrect assumptions from from what was essentially a truthful statement.....the panels do run 25 degrees hotter than ambient,but the shading effect more than compensates,aided by the fact that heat rises.Life goes on! Have a great day,and safe travels. Cheers.
Cupie said
02:48 PM Apr 7, 2018
Hi ..
I was interested in the discussion of the cooling effect of roof mounted solar and having a bit of time on my hands I decided to put it to the test.
I have one 200w panel installed on the roof of my old Jayco Westport using the commercial panel fixing shoes in the centre & some aluminum brackets on the outside edges to keep the panel level & allow for the curved roof.
The results of a series of temperature readings using my Digital Infrared thermometer on a beautiful Autumn day in Brisbane are on the attached s/sheet.
Draw your own conclusions & perhaps do some readings on your own set up.
Oops .. left out a column of appx ambient temps
-- Edited by Cupie on Saturday 7th of April 2018 02:53:21 PM
Cupie - maybe I need to apologise for apologising.
Regards
Cupie said
08:30 AM Apr 9, 2018
Hi ..
I was interested in the discussion of the cooling effect of roof mounted solar and having a bit of time on my hands I decided to put it to the test.
I have one 200w panel installed on the roof of my old Jayco Westport using the commercial panel fixing shoes in the centre & some aluminum brackets on the outside edges to keep the panel level & allow for the curved roof.
The results of a series of temperature readings using my Digital Infrared thermometer on a beautiful Autumn day in Brisbane are on the attached s/sheet.
Draw your own conclusions & perhaps do some readings on your own set up.
Oops .. left out a column of appx ambient temps ... edit 3 Pasted in a wrong set of figures. Fixed & added a summary to make it easier to draw c
-- Edited by Cupie on Saturday 7th of April 2018 02:53:21 PM
robol said
11:20 AM Apr 9, 2018
Hi Hako. Thanks, but not necessary.
Cheers Rob.
Hi Cupie. Temp. difference might have something to do with the size of the air space between underside of the glass and the roof surface. I only have to feel the inside of the ceiling, both under the solar panels and where there aren't any to tell which is cooler. I do have a large air gap on mine as well as Thermoshield on the roof.
Cheers Rob.
-- Edited by robol on Monday 9th of April 2018 11:22:46 AM
yobarr said
11:41 AM Apr 9, 2018
robol wrote:
Hi Hako. Thanks, but not necessary.
Cheers Rob.
Hi Cupie. Temp. difference might have something to do with the size of the air space between underside of the glass and the roof surface. I only have to feel the inside of the ceiling, both under the solar panels and where there aren't any to tell which is cooler. I do have a large air gap on mine as well as Thermoshield on the roof.
Cheers Rob.
-- Edited by robol on Monday 9th of April 2018 11:22:46 AM
Hi Rob...that is indeed correct.Set the panels up so there is about 100-125mm clearance underneath the panel and the difference is amazing....up to 38% cooler,according to my research.Too many panels installations have the panels almost touching the roof.....obviously they will transfer heat to the van!! My roof is almost fully covered in Solar,and the van is a lot cooler than it was before I installed them.....and if needed,I can run the AC whenever I want!
Cheers
T1 Terry said
03:43 PM Apr 9, 2018
Something missed by all those comparing house mounted panels to RV roof mounted panels, the angle they are mounted. On a house roof there is a natural heat removal as the air moves from the cooler lower end of the panel to the hotter higher end of the panel, heat rises.
Now look at the flat mounted RV panel, if heat rises where can it go? There is a frame around the panel underside that traps the hot air so it can not shift the heat away. Try taping a thermocouple on the underside of a solar panel and see just how hot it gets, that 50mm clearance does reduce the convection heat transfer to the roof, 100mm would have an even greater effect but the risk of a large array turning into a sail in high wind and ripping it off the roof must also be taken into consideration.
As far as the product "It's So Cool" one of the heat reflecting paints on the market, my Kombi, 36 ft bus, Mazda T3500 and Hino RB145A all have their roofs painted with it and the difference is quite amazing. It comes with a product called Prolon, a clear coat to stop the dirt embedding itself into the off white paint. The instructions say to apply one coat, we all know better than to follow the instructions and there was a heap spare, so I applied 3 coats to the Kombi pop-top roof ... it looks like it has suffered severe sunburn and the clear skin is peeling in spots, but not the first coat cause it soaked into the white paint. I learnt my lesson and the other vehicles only got one coat of the Prolon :lol:
T1 Terry
Cupie said
11:49 PM Apr 9, 2018
robol wrote:
Hi Hako. Thanks, but not necessary.
Cheers Rob.
Hi Cupie. Temp. difference might have something to do with the size of the air space between underside of the glass and the roof surface. I only have to feel the inside of the ceiling, both under the solar panels and where there aren't any to tell which is cooler. I do have a large air gap on mine as well as Thermoshield on the roof.
Cheers Rob.
-- Edited by robol on Monday 9th of April 2018 11:22:46 AM
Yes, I agree with the air gap comment but assumed that the commercial mounting feet would be the optimal size. Also agree with Ti Terry's comment about the sail effect.
I don't think that I read any supplier's mounting instructions. Learnt as a Techo many many years ago that you only read instructions when everything else fails. LOL But I have them in a lovely folder in the van with all of my other 12v paperwork including my complete wiring diagrams, just in case. Might be of help to the van's next owner.
rockylizard said
03:58 PM Apr 10, 2018
Gday...
Jest fer interest, praps. Cupie's Temperature Readings -
Cheers - John
yobarr said
10:39 AM Apr 12, 2018
rockylizard wrote:
Gday...
Jest fer interest, praps. Cupie's Temperature Readings -
Cheers - John
Hi John...Very nice pretty pictures,but they are the results of one mans experiment.I have no doubt that the the intentions were good,but the results fly in the face of the facts! Sorry. Cheers.
T1 Terry said
12:44 PM Apr 12, 2018
Hi Yobarr, do you have other actual tests and results that show different facts so the two results can be compared?
T1 Terry
yobarr said
05:10 PM Apr 12, 2018
T1 Terry wrote:
Hi Yobarr, do you have other actual tests and results that show different facts so the two results can be compared?
T1 Terry
Hi Terry....I dont have tests,but I have had dealings with Solar installers etc for many years.It is generally accepted that panels will keep a house significantly cooler than it was before panels were installed,and I have actually had friends cover the whole roof of their tin-shed workshops to keep temperatures down.I am unaware of what gap the OP has under his panels,but I have 6 (150mm to younger readers!) under mine.Surprisingly,they havent acted like a sail and gone walkabout,nor have they had air trapped under them
If the panels are mounted straight onto the roof,which I have seen,then common sense would dictate that the heat may be trapped,and the roof surface will see an increase in temperature,but if there is a decent gap there will be no problem. Happy,and safe,travels. Cheers.
T1 Terry said
06:09 PM Apr 14, 2018
Yeah, a sloping roof will get air movement as I mentioned before, but flat mounted on an RV roof will not get the same amount of air movement so trying to compare a house or shed roof to an RV roof isn't quite the same comparison. Yes, you could mount the panels 150mm above the roof, but not many RV owners would see that as an attractive addition to their rig. In fact I have a lot of them who request the panels to be mounted so they can't be seen from the sides, front or rear, so 150mm above the roof would just about eliminate any spots on the roof. Most of these jobs generally go for the light weight flexible panels because they mount about 16mm above the roof in total, 3mm aluminium foot plate, 10mm Lexan thermoclear sheet and 3mm thick panel. Tests using a thermocouple placed under the Lexan sheet http://www.ampelite.com.au/products/lexan-multiwall-polycarbonate/lexan-thermoclear/ and a second thermocouple placed in the shadow but taped to the aluminium roof sheeting show the roof under the thermoclear is actually cooler than the roof in the shade, yet the underside of the panel resting on the top face of the thermoclear is 70*C. In this case it is the Lexan Thermoclear providing the insulation, not the shade from the solar panel.
T1 Terry
yobarr said
09:24 PM Apr 14, 2018
T1 Terry wrote:
Yeah, a sloping roof will get air movement as I mentioned before, but flat mounted on an RV roof will not get the same amount of air movement so trying to compare a house or shed roof to an RV roof isn't quite the same comparison. Yes, you could mount the panels 150mm above the roof, but not many RV owners would see that as an attractive addition to their rig. In fact I have a lot of them who request the panels to be mounted so they can't be seen from the sides, front or rear, so 150mm above the roof would just about eliminate any spots on the roof. Most of these jobs generally go for the light weight flexible panels because they mount about 16mm above the roof in total, 3mm aluminium foot plate, 10mm Lexan thermoclear sheet and 3mm thick panel. Tests using a thermocouple placed under the Lexan sheet http://www.ampelite.com.au/products/lexan-multiwall-polycarbonate/lexan-thermoclear/ and a second thermocouple placed in the shadow but taped to the aluminium roof sheeting show the roof under the thermoclear is actually cooler than the roof in the shade, yet the underside of the panel resting on the top face of the thermoclear is 70*C. In this case it is the Lexan Thermoclear providing the insulation, not the shade from the solar panel.
T1 Terry
Hi Terry...yeah,I can understand your comments about aesthetics ,and peoples concerns,but I am not so precious! I have 3x190 watt panels across the front sloping section of the van,and another 6x190 panels on the roof.(Van is just under 6 metres) Only 8 panels are connected,with the other one simply being a spare.Along with the 4 seasons (?) vent,a vent above the ensuite,and the satellite TV aerial (Satking) there is very little of the roof that is exposed to the sun! Heaps cooler than it was before I fitted them all! Cheers.
T1 Terry said
02:19 PM Apr 15, 2018
Sounds like you've had a win yobarr, no wife complains and a cool van, can't ask for more than that eh :lol:
Has anyone heard or used this product on the roof of a caravan or motor home ?
They claim reduces temperatures by up to 45%
converts rust and increases metal life
reduces roof maintenance by up to 80%
I can be contacted on togo4950@gmail.com if any one can find further information
If you find out anymore info pass it on here on the forum mate
Bagmaker must be spying on me :)
Stay safe
Has anyone heard or used this product on the roof of a caravan or motor home ? Yes on my 11mt bus
They claim reduces temperatures by up to 45% Does reduce temp, but not that much in practice - you can definitely notice the difference though.
converts rust and increases metal life Does NOT convert rust, it's just an acrylic emulsion with ceramic micro balls, not a rust converter. Any paint prolongs metal life.
reduces roof maintenance by up to 80% Compared to what?
If your existing paint is loose or flaking you will need to prepare it very well.
I completely bare metaled my roof, then etch primed it, then 2 very thick coats of Thermoshield (30lts sprayed on with an airless gun) then 2 coats of Weathershield Gloss (same application).
If you don't top coat the Thermoshield with something it will yellow and powder off.
I actually mixed my Weathershield with Bondcrete, a trick I learned doing roof restorations many years ago.
-- Edited by El Gringo on Thursday 5th of April 2018 05:19:15 PM
I used THERMALATE, which is in a crystalline form. I mixed this ( app. 1.5 bags ) in with the two pack paint and applied it by roller, two or three coats. I left the sides above gutter line smooth and ran a line of masking tape along the edge of the curve. This looks better and is easier to keep clean. I also covered as much of the roof with solar panels as possible and left enough room underneath them to clean the roof.
I am not sure if it's the Thermalate or the solar panels but I am happy so far.
Worth the effort.
Solar panels actually make the roof of the caravan hotter, not cooler - the backside of a PV solar panel is typically about 30C hotter than ambient, assuming 0.8 kW/m^2 irradiance.
The source of this data is:
https://www.quora.com/Is-the-underside-of-a-solar-panel-hot
Good Luck.
Thanks for the feedback i shall try the application when we get two days of fine weather in a row
Rubbish......Solar panels on the roof of a house,with around 150mm clearance to allow air to circulate,will keep that house up to 38% cooler than if the sun shines straight onto the roof.Fact.We all know that panels run about 25 degrees hotter than ambient.I have 1520 watts of Solar on my van to run my 2.5kw AC,which I rarely have to use because of the panels keeping the sun off the roof.Think about it.....hot air rises,and with a van under 6 metres long,there is not much roof uncovered. Safe,and cool,travels. Cheers.
-- Edited by yobarr on Friday 6th of April 2018 10:11:30 AM
Hi El Gringo et al
As I understand the theory of Thermoshield, it relies on the surface properties of the 'special' paint to achieve the reduction in roof temperature. So if you over coat it with a normal paint that will not work. The micro spheres etc and the thickness has just a minor effect to make the temperature lower. I would say do not do it like that IMHO.
I have researched it a bit and have not been convinced it is better than pure white roof paint. Being much more expensive it may not be worth it. The comparison results claimed are made often, as usual, by comparing apples with oranges. As El Gringo said it has no other magic properties that will make the roof better than new.
Jaahn
Yes they go on a bit on the website about the surface properties, but as you said it's virtually the same as any white paint.
The thermal properties are the ceramic microballs mixed into the paint, this is the only advantage over any other white paint, and surprisingly they do actually work - and perhaps not surprisingly they work better the more (thicker) you put on.
As far as overpainting affecting it, well they even offer a clear coat to help prevent the discolouring and oxidising of the paint themselves.
So for me (and I am a painter by trade) I have the benefit of the insulating paint and the benefit of the glossy white Weathershield on top - 3 years now and going very well.
Cheers,
Regards
cheers Craig
Hi Denis....All is good and this shows how easy it is to draw incorrect assumptions from from what was essentially a truthful statement.....the panels do run 25 degrees hotter than ambient,but the shading effect more than compensates,aided by the fact that heat rises.Life goes on! Have a great day,and safe travels. Cheers.
Hi ..
I was interested in the discussion of the cooling effect of roof mounted solar and having a bit of time on my hands I decided to put it to the test.
I have one 200w panel installed on the roof of my old Jayco Westport using the commercial panel fixing shoes in the centre & some aluminum brackets on the outside edges to keep the panel level & allow for the curved roof.
The results of a series of temperature readings using my Digital Infrared thermometer on a beautiful Autumn day in Brisbane are on the attached s/sheet.
Draw your own conclusions & perhaps do some readings on your own set up.
Oops .. left out a column of appx ambient temps
-- Edited by Cupie on Saturday 7th of April 2018 02:53:21 PM
Cupie - maybe I need to apologise for apologising.
Regards
Hi ..
I was interested in the discussion of the cooling effect of roof mounted solar and having a bit of time on my hands I decided to put it to the test.
I have one 200w panel installed on the roof of my old Jayco Westport using the commercial panel fixing shoes in the centre & some aluminum brackets on the outside edges to keep the panel level & allow for the curved roof.
The results of a series of temperature readings using my Digital Infrared thermometer on a beautiful Autumn day in Brisbane are on the attached s/sheet.
Draw your own conclusions & perhaps do some readings on your own set up.
Oops .. left out a column of appx ambient temps ... edit 3 Pasted in a wrong set of figures. Fixed & added a summary to make it easier to draw c
-- Edited by Cupie on Saturday 7th of April 2018 02:53:21 PM
Hi Hako. Thanks, but not necessary.
Cheers Rob.
Hi Cupie. Temp. difference might have something to do with the size of the air space between underside of the glass and the roof surface. I only have to feel the inside of the ceiling, both under the solar panels and where there aren't any to tell which is cooler. I do have a large air gap on mine as well as Thermoshield on the roof.
Cheers Rob.
-- Edited by robol on Monday 9th of April 2018 11:22:46 AM
Hi Rob...that is indeed correct.Set the panels up so there is about 100-125mm clearance underneath the panel and the difference is amazing....up to 38% cooler,according to my research.Too many panels installations have the panels almost touching the roof.....obviously they will transfer heat to the van!! My roof is almost fully covered in Solar,and the van is a lot cooler than it was before I installed them.....and if needed,I can run the AC whenever I want!
Cheers
Now look at the flat mounted RV panel, if heat rises where can it go? There is a frame around the panel underside that traps the hot air so it can not shift the heat away. Try taping a thermocouple on the underside of a solar panel and see just how hot it gets, that 50mm clearance does reduce the convection heat transfer to the roof, 100mm would have an even greater effect but the risk of a large array turning into a sail in high wind and ripping it off the roof must also be taken into consideration.
As far as the product "It's So Cool" one of the heat reflecting paints on the market, my Kombi, 36 ft bus, Mazda T3500 and Hino RB145A all have their roofs painted with it and the difference is quite amazing. It comes with a product called Prolon, a clear coat to stop the dirt embedding itself into the off white paint. The instructions say to apply one coat, we all know better than to follow the instructions and there was a heap spare, so I applied 3 coats to the Kombi pop-top roof ... it looks like it has suffered severe sunburn and the clear skin is peeling in spots, but not the first coat cause it soaked into the white paint. I learnt my lesson and the other vehicles only got one coat of the Prolon :lol:
T1 Terry
Yes, I agree with the air gap comment but assumed that the commercial mounting feet would be the optimal size. Also agree with Ti Terry's comment about the sail effect.
I don't think that I read any supplier's mounting instructions. Learnt as a Techo many many years ago that you only read instructions when everything else fails. LOL But I have them in a lovely folder in the van with all of my other 12v paperwork including my complete wiring diagrams, just in case. Might be of help to the van's next owner.
Gday...
Jest fer interest, praps. Cupie's Temperature Readings -
Cheers - John
Hi John...Very nice pretty pictures,but they are the results of one mans experiment.I have no doubt that the the intentions were good,but the results fly in the face of the facts! Sorry. Cheers.
T1 Terry
Hi Terry....I dont have tests,but I have had dealings with Solar installers etc for many years.It is generally accepted that panels will keep a house significantly cooler than it was before panels were installed,and I have actually had friends cover the whole roof of their tin-shed workshops to keep temperatures down.I am unaware of what gap the OP has under his panels,but I have 6 (150mm to younger readers!) under mine.Surprisingly,they havent acted like a sail and gone walkabout,nor have they had air trapped under them
If the panels are mounted straight onto the roof,which I have seen,then common sense would dictate that the heat may be trapped,and the roof surface will see an increase in temperature,but if there is a decent gap there will be no problem. Happy,and safe,travels. Cheers.
Yeah, a sloping roof will get air movement as I mentioned before, but flat mounted on an RV roof will not get the same amount of air movement so trying to compare a house or shed roof to an RV roof isn't quite the same comparison.
Yes, you could mount the panels 150mm above the roof, but not many RV owners would see that as an attractive addition to their rig. In fact I have a lot of them who request the panels to be mounted so they can't be seen from the sides, front or rear, so 150mm above the roof would just about eliminate any spots on the roof.
Most of these jobs generally go for the light weight flexible panels because they mount about 16mm above the roof in total, 3mm aluminium foot plate, 10mm Lexan thermoclear sheet and 3mm thick panel. Tests using a thermocouple placed under the Lexan sheet http://www.ampelite.com.au/products/lexan-multiwall-polycarbonate/lexan-thermoclear/ and a second thermocouple placed in the shadow but taped to the aluminium roof sheeting show the roof under the thermoclear is actually cooler than the roof in the shade, yet the underside of the panel resting on the top face of the thermoclear is 70*C. In this case it is the Lexan Thermoclear providing the insulation, not the shade from the solar panel.
T1 Terry
Hi Terry...yeah,I can understand your comments about aesthetics ,and peoples concerns,but I am not so precious! I have 3x190 watt panels across the front sloping section of the van,and another 6x190 panels on the roof.(Van is just under 6 metres) Only 8 panels are connected,with the other one simply being a spare.Along with the 4 seasons (?) vent,a vent above the ensuite,and the satellite TV aerial (Satking) there is very little of the roof that is exposed to the sun! Heaps cooler than it was before I fitted them all! Cheers.
T1 Terry