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boondockdad · 06-27-2010, 08:18 AM

I'm all for making the 'stream more efficient... so I did some simplified calculations, based on my 30' S/O, to get some perspective

640 s.f. insulated metal panel
72 s.f. single pane glass
19 s.f. rib channel

If we assume R values of 3.25 for the insulated metal panel, .91 for the glass, and .61 for the ribs, using BTU/hr=area(temp delta)/R value

2,484 BTU/hr for insulated metal panel
1,028 BTU/hr for the single pane glass
404 BTU/hr for the rib channels

So, yeah, when you're dealing with compact units like our 'streams, every little bit helps, but the infiltration alone on my unit would blow-away any small efficiencies gained in providing a thermal break at the structural channel and skin.

2airishuman · 06-27-2010, 09:24 AM

Quote:

Originally Posted by finalcutjoe

... the infiltration alone on my unit would blow-away any small efficiencies gained in providing a thermal break at the structural channel and skin.

agree completely, and don't forget the ceiling vents, furnace and misc storage doors.

or the completely OPEN AIR fridge venting and loose install.

also keep in mind YOUR unit already has butyl tape between the ribs and OUTER SKIN...

it has "thermal break" tape, a/s has been using that approach since the mid 90s.
__________

the real issue for most of the older streams at the monty stage is reducing how HOT the inner skin gets in blazing sun.

that's really the issue many are trying to improve (hot to touch inner skin)

along with the cost of heating/cooling older units.

cheers
2air'

Bob Thompson · 06-27-2010, 10:38 AM

The real key is in the equasion listed as delta "t" or difference in degrees between the outside skin and the inside air temperature. It doesn't matter to the calculation if it's 110 degrees outside or 38 degrees outside if the inside temperature is set to be 74 degrees. There was a time when I was fluent in these calculations but that knowledge has long since escaped me, but I do remember that the conducted heat or cold was a larger portion than just the R-Value of the rib.

mbattin · 06-28-2010, 01:52 PM

Bob, you are dead on there...R-Value has little to do with the thermal break, its two different thermal conditions. (I know that stuff is in some books I have but the bottom line is, R-value is one thing, thermal bridging is another, you can have an R-60 wall, that with alum to alum conections outside to in is the equiv of having radiator fins built into your wall.

reinergirl · 10-01-2013, 05:55 PM

I realize this is an older thread but was wondering what you all are currently using for a thermal break on the ribs?

If you have used a thermal break, what did you use and are you happy with it?

I'm thinking of using a ceramic insulating paint like this.
Buy Hy-Tech Insulating additive for paint and make your paint INSULATE

cwf · 10-01-2013, 07:02 PM

Quote:

Originally Posted by reinergirl

I realize this is an older thread but was wondering what you all are currently using for a thermal break on the ribs? If you have used a thermal break, what did you use and are you happy with it? I'm thinking of using a ceramic insulating paint like this. Buy Hy-Tech Insulating additive for paint and make your paint INSULATE

Hmmm. Smart thinking there Lady!

Wabbiteer · 10-01-2013, 07:20 PM

I have that paint & the additive powder and was considering priming the whole inside of the shell with a bonding paint with the beads in it, but sealing the seams and rivets probably will be enough. Where it excels is dodging sun heating as a first layer of defense, or covering a huge expanse of interior surfaces for some small degree of near-painless energy savings. The lower temperature differentials in small spaces may not be the best use - though painting the both sides of the liner sheets might yet be in my trailers plan... except...

Using those as a thermal break? The spheres are pretty tough so in between aluminum it'd be like sandpaper, the soft liner sheets would conform to the the texture with vibration and temperature changes and ever-so-slightly loosen, and/or black aluminum oxides would be produced blah blah..

But wait, there's more! Painting the liners and having a mouse-fur-soft foam tape on the rib to protect the paint.... You've got me thinking, THANKS

Also - note they recommend spraying it to help the micro-spheres to settle in an orderly matrix. Just a note when you're wish-booking on the product

reinergirl · 10-12-2013, 05:14 PM

Quote:

Originally Posted by Wabbiteer

But wait, there's more! Painting the liners and having a mouse-fur-soft foam tape on the rib to protect the paint.... You've got me thinking, THANKS

Also - note they recommend spraying it to help the micro-spheres to settle in an orderly matrix. Just a note when you're wish-booking on the product

Thanks for the ideas Wabbiteer! No way am I masking off the ribs to spray lol.

Aren't you concerned that a soft foam tape will cause the rivet bond to be weak, not to mention you might end up with dimples..... Hmmm

I'm still trying to find something.....

Wabbiteer · 10-12-2013, 09:17 PM

The pre-dimpled 40-year-old liners in my trailer might consider 1/16" extra-soft foam tape an elective surgical facelift.

The 'pull' clamping force of a 1/8" rivet is minimal, yet is additive to the physical force of the gorilla pressing the rivet/sheet assembly home. Thus a 2-4psi force for 25% compression over a birdseye circle around each rivet (not much more to collapse the foam completely) will, with a (my) nearly disposable trailer project, not be a problem in this instance. Let's insert the standard disclaimer 'not recommended for anyone else' certainly.

No need to mask off the rib face - who is gonna see the overspray? The work will be preparing the aluminum so something will permanently bind to it, it takes chemically bonding a passive & inert layer between aluminum and your flavor of paint/sealer/adhesives to enjoin a lasting union. For your little-bit 26' trailer that's only about 425 linear feet or 28-30sqft of rib face to coddle...

FC7039 · 10-12-2013, 09:50 PM

I would put any break on the ribs, both on the inner and outer faces of the ribs, but not at the rivets. The heat transfer through the rivets and close to them will still happen but you will retain the rivet clamp and strength. Refrain from any coating on the skins as this defeats aluminum's poor radiation of heat. The cleaner the skins and even better, shinier to lessen surface area the better. But do seal the rivets and seams but do not over do it. Fill the gap with an insulation and if you can add a foil barrier as it's surface will be a better radiant barrier than either of the skin surfaces unless you polish the inward not visible skin and who would do that.