EHP roll board???

[John316]

Is EHP roll board really worth it? They say, on their website, that it will cut heat down 50% to 75%. What does that mean? Does anybody have real life experience? How many R's does it have?

We are thinking about using it in the bedroom (in addition to the inch and a half foam) to keep the radiated heat down.

Let me know if I can supply any more info.

God bless,

John

[VanTare]

John316,on my coach the converter Vantare used a foil type to cover every sq in on the inside over the foam this is by far the best insulated coach I have owned.I do not know the proper name for it but it is called dead space foil,call Vantare in Sanford Fl and they  may give the name if it is not one of their trade secrets.Unless the EHP roll board has changed in the last few years it has no R value

David

[rv_safetyman]

John I used to sell roll board and other products from E.H.P (http://engineheatprotection.com/).  I decided not to continue selling the product, as it was a slow mover for me.

I am a firm believer in the product at least for some applications.  I use it on my exhaust components and it is fabulous.  I have seen demonstrations where you put some roll board in the palm of your hand, put some solder on it and melt the solder without burning your hand.  The product comes out of the space program.

Now, having said that, I am not sure how it works for insulating your bus.  Heat transmission is a complex science.  The E.H.P advertising in Bus Conversion magazine shows a bus that was insulated with roll board.  I talked to the owner at one of the Bus Conversion Rallies several years ago and he was very pleased.

To me it makes sense to use the product on the roof interior skin and then add "normal" insulation.  My plan when I do my ceiling (currently as it came with the bus) is to use the roll board and the use rigid foam.

I hope that someone with a "thermal science" background will reply to this thread.

Roll board is pretty darn expensive, but I think it is worth it.

Jim

[luvrbus]

Jim, I have a 1/2 roll of the board if you need it I will bring it to Quartzsite I think the stuff is good for engine compartments if you cover it with a protective materail I have it under the lead floors in the bedroom and it cuts the heat down but 50% to 75%  I doubt if that is fact         Good luck

[rv_safetyman]

Warning:  technical diatribe to follow 

Those of you who know me, know that my previous post was a bit shallow for an engineer .

Also, you probably know that I try to make sure that I post a response that will allow folks to dig deeper if they wish.  So here goes (skip this post if you don't like technical discussions)

As I mentioned, heat transfer is a complex science.  Most of us know that heat is transferred by three methods:  radiation, conduction and convection.  I found a pretty good site that explains these at a presentation level that is understandable:  http://sol.sci.uop.edu/~jfalward/heattransfer/heattransfer.html. 

Classic insulation calculations rely on a value called thermal conductivity.  In the past, when I tried to research thermal conductivity values for ceramic insulation, I found very little information.  When you look at the table on this site (http://matse1.mse.uiuc.edu/ceramics/prin.html) you will see that ceramic insulation does not rate all the great.  However, we know that it is a tremendous insulator (used on the space shuttle).

Most folks who sell any form of ceramic insulation will not give a thermal conductivity rating.

So, what am it trying to say?  I guess the easiest way to say it is that the ceramic insulation science does not lend itself to classic heat transfer calculation.  At least that is my take on it.

Jim

[rv_safetyman]

Clifford, I still get calls from folks who want small amounts of the product for special projects.  I have some left, but not as much as I need for when (if?) I get to the ceiling. 

If you will bring it to Quartzsite, I will be glad to buy it from you.

Jim

[JohnEd]

About those methods of heat transfer:

Windows admit heat mostly by radiation transfer.  Sun loading is a real killer.  That light reflective silver/gold coating reduces the solar heat throughput by 70 to 90% depending on mfr.  A must have!  Windows also admit and lose heat by "conduction".  Thermo pane reduces this by 50% or so.  In really spendy thermo pane windows the frame is also interupted with a thermo barrier as the frame can "conduct" a lot of heat either way.

The roof is a serious issue.  Pure white will reflect something like 50% of the heat load from sunlight.  As you move away from white you must increase the tonnage of the AC and at flat black you have arrived at the "uncoolable".  Pure white roof is a must.  That is the way to reduce the heat input by radiant loading of the roof.  Conductive throughput is defeated by R value.  Lets repeat that...R value!  The conductive aspect is there 24/7 and heat trans will be inhibited going either way.  The radiant load is simply added to it.  You need more R value in the ceiling because it will get higher loads than any other part of the coach.  Foam is the ticket for conduction and has no peer and, in addition, the foam board has foil backing to reflect radiant heat.  Still the spray foam out performs the board in terms of R value but I don't think the radiant factor of the foil is included.

Now that silver bubble wrap has a lot of radiant heat rejection but not much R value.  Logically, if you applied it to the exterior of the coach you could reduce the radiant loading by 50% or so.  That is really significant but you can do that with white paint.  If you apply it to the "inside" surface of the foam you can get a benefit from it reflecting heat back into the coach.  Probably as much as laying in al. foil, but the board already has that on it.  The white roof will already reduce the load and bubble wrap under the metal sees mostly conducted heat and it does little with that.  The inside of an engine bay is a terrific spot for the silver bubble stuff and will seriously cool the BR and interior foam will do the rest back there.

I said before that if the stuff doesn't have a R value advertised as "R VALUE" without qualifiers such as "apparent", "effective" or "equal", etc. then it has no R value and has very limited applications.  Does NOT mean that it is worthless, just that it has limited apps.  I find it difficult to believe that ceramic wool has no specified R value but its application is with insulating items that are heated to in excess of one thousand degrees.  It replaced asbestos, mainly and has no way near the R value of poly foam which ignites.

Floors are a problem also and typically have a higher R value applied than the walls.  Conduction flow only so here again R value rules no matter what color you paint it.

It is OK with me if I am wrong.  I am not an engineer and do not take crit. professionally.   Make any counterpoint you can and please clarify any blunders.

HTH,

John

Spray foam your ceiling or at least foam board it and paint the exterior white. 

[rv_safetyman]

Hi John.  I don't disagree with almost everything you said. 

As I mentioned, classical heat loss calculations are based on thermal conductivity values.  Your r-value is the reciprocal of the K-value (thermal conductivity).  The relationships are as follows:

Thermal Conductivity (k-values) Units = W/mK
Thermal Resistivity (r-values) Units = mK/W
Both of these equations are for 1 meter thick material.  You will often see thermal conductivity equation in the form of W/m(squared)K so that thickness of the material is easier to address.  R values also are described by using square meters (to address thickness).  The word description is:  "The world-wide definition of R-value is kelvin square meters per watt (K·m²/W), using the SI system"

Now all of that sounds very scientific, and I guess it is.  However, there are some folks that will challenge the science a bit.  For example, log homes defy the calculations.  Wood is not a terribly good insulator and yet log homes can be fairly energy efficient.  There are lots of theories why this is.  Take a look at:  http://www.nachi.org/loghomes.htm

I have followed heat transfer theory a bit over the years, and the more I read, the more confused I get.  The building industry takes a very cut and dried approach to the subject.  That works well with conventional materials.  However, the basic theory may get a bit off target for more advanced materials.

Another example that came up on this board (I think) was a coating with ceramic beads.  We could all buy into the fact that it would help with reflection of the heat off the roof.  However, someone on this board painted the inside of the bus and reported a very large reduction of radiated heat.  I don't think that basic heat transfer theory would describe what this person experienced.

Bottom line, R-values and K-values are good tools, but my opinion is that it takes more advanced theory to address non-traditional materials. 

So, lets leave the door open for "alternative insulation"

I am going to try to reach my contact at EHP (I think they may have changed ownership in the last few years) and see if he can give us a better answer

Can you all tell that you have my "engineer juices flowing"

Jim

[niles500]

**** For example, log homes defy the calculations.  Wood is not a terribly good insulator and yet log homes can be fairly energy efficient

Jim - I think that can be explained as "thermal massing", i.e. materials such as adobe - HTH

[gus]

My understanding of R value is that air is the best insulator. I'm not talking about radiant barriers, a different thing entirely to me.

If this is true, anything that traps air is a good insulator. This makes me think that bubble foil is pretty good. On the other hand, since the foil is Al it is also a very good conductor of heat.

So, I'm pretty confused about bubble foil. The PO installed it in my airplane but I'm not sure if it is worthwhile since it is installed under the fabric airframe cover which won't ever get very hot?

I have an engineering degree too, but I usually try to keep it quiet!! Engineers tend to write things few people can understand, much like computer nerds!! Their method seems to be to never use a word where a paragraph or page will do!

[John316]

Thanks for all of the posts and info. I can't say what I really think, as I am still digesting the info. Thanks Jim and John for the detailed answers.

We have sprayed foam inside (2.5in on the roof, and 1.5in on the walls). Our bus is painted white.

I will post more later.

Thanks again.

God bless,

John

[JohnEd]

Whew!   What a relief!

John

[JohnEd]

Gus,

Air is not the best insulator, vacuum is.  Air beats out most everything else, though.  I foam you have a series of bubbles stacked up and that slows down the transfer.  Foams are all excellent and spray foam seems to be at the top.  I wonder if that is because it is the least dense and has the greatest ratio of bubbles to solid material?  My problem with bubble wrap is that it is only one bubble thick and that shouldn't be expected to approach the resistivity of something like foam.  Given that fiberglass impedes the convection flow I would think that a few inches of fiber glass would out perform bubble.  Did you get that "think" part?

After all that, I was in camping world the other day and they had a display for the silver bubble wrap.  The display had a closed tube that you were supposed to insert your hand into to "experience" how well bubble material worked.  I inserted my hand and it got so hot so fast that I inspected the tube for batteries.  I have no explanation for this stuff and what little I know of physics doesn't help.

Aluminum is a great conductor and that foil backing is as well.  It isn't there for the R value and it counts little either way as its thickness is measured in "mils".  It provides a "reflective" performance factor that can't be added to the R value but is valid and usefull never the less.  I don't think it would help much with keeping you bus cool but I think it would contribute to your keeping the place warm in winter when the heat radiates out of the living area.

[Dallas]

John,
Actually, my bus is lined inside with Reflectix™ which is foil-bubble-foil and it works quite well at both cooling and heating.
When I was installing it in the bedroom the outside temp was a little over 100° and the inside temp, even with a 8KBtu window air going was 115° about 5 minutes after I had the Reflectix™ installed the temp had dropped to around 95° and 20 minutes later was in the 80° range. I used my IR temp gun on the inside and outside of the Reflectix™ and the temp difference was over 40°.
By the way, this is under 1.5" of Blue polystyrene insulation board with around 1/4" dead air space between the Reflectix™ and the insulation.

I hope that helps.

Dallas

Gus,

Air is not the best insulator, vacuum is.  Air beats out most everything else, though.  I foam you have a series of bubbles stacked up and that slows down the transfer.  Foams are all excellent and spray foam seems to be at the top.  I wonder if that is because it is the least dense and has the greatest ratio of bubbles to solid material?  My problem with bubble wrap is that it is only one bubble thick and that shouldn't be expected to approach the resistivity of something like foam.  Given that fiberglass impedes the convection flow I would think that a few inches of fiber glass would out perform bubble.  Did you get that "think" part?

After all that, I was in camping world the other day and they had a display for the silver bubble wrap.  The display had a closed tube that you were supposed to insert your hand into to "experience" how well bubble material worked.  I inserted my hand and it got so hot so fast that I inspected the tube for batteries.  I have no explanation for this stuff and what little I know of physics doesn't help.

Aluminum is a great conductor and that foil backing is as well.  It isn't there for the R value and it counts little either way as its thickness is measured in "mils".  It provides a "reflective" performance factor that can't be added to the R value but is valid and usefull never the less.  I don't think it would help much with keeping you bus cool but I think it would contribute to your keeping the place warm in winter when the heat radiates out of the living area.

[JohnEd]

Dallas,

It does help.  Really!  It doesn't explain it but it helps to KNOW that there are exceptions to the rules, at least the ones that I am vaguely aware of, that provide alternatives.  I sure hope some of the engineers can chime in and clear the air.  At this point I can imagine some nontechys having trouble "figuring" which way, how thick and etc.

I don't know what "blue foam" is.  Considering that the spray stuff is touted as the absolute best, I assume that it performs to some degree less well than spray.  And that might well be a fraction not worth considering.  What is the R value on the blue?  Does that Reflectex have a R value?

Thank you for your comment and information.  Hope to hear more from you and others.  It helps all.

John