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 > Anyone interested in 83 Pace Arrow Tear down and Rebuild?

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fulltimin

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Posted: 06/12/18 08:48am Link  |  Quote  |  Print  |  Notify Moderator

Bruce Brown wrote:

I can't help you with how the Reflectic worked in the warm weather, I never used it when it was warm.

We've also since sold it so I can't even check for you.



Thanks for the update, Bruce.


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fulltimin

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Posted: 06/12/18 08:50am Link  |  Quote  |  Print  |  Notify Moderator

joerg68 wrote:

Dual roofs with air circulating between the layers are a thing in bus/coach construction.

See this one for example: http://uploads.tapatalk-cdn.com/20160118/21c313db9a4a55ea533d33e38f1e998c.jpg

(if the link does not work, do a google search for "Dual Roof MC-5Cs")

It is done for cooling. How well it works when an RV is stationary, I don't know. Some use their solar modules as a second "shadow roof".


Thanks for the post. I had seen some of the MC-5C's with the double roof. They were originally bound for Saudi Arabia. I figure it it helps there, it would help here during the warmer months.

fulltimin

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Posted: 06/12/18 08:57am Link  |  Quote  |  Print  |  Notify Moderator

fulltimin wrote:

Ideally, having an air space between the top of the roof and the insulation, would go a long way to eliminate the "oven" effect. Same thing with the walls.

If you look at how a "space blanket" works, there is very little "insulation value" to it. But the reflective properties of said blanket, can keep you from freezing in cold weather, by reflecting your own body heat back towards you.

Just thinking out loud here, but, using the space blanket principle, it would seem that if the roof and walls were constructed of an outer covering, then an air space, with "space blanket" reflective film and then insulation, then another "space blanket" reflective film, then another air space, and then the inside wall, (paneling or whatever), probably would be about as good as one could get.

That would apply reflective towards the sun in the summer, and reflective towards the inside heat during the winter. Sounds like the best of both worlds.


Now, before we go any farther, I just want to clarify something here. When I said using the reflective/space blanket technique, I was implying, but not stated, that the insulation between the two, would be a type of hard foam board, with the reflective glued to either side of that insulation.

It is NOT a good idea to use a vapor barrier, (which is what those reflective barriers would be), on both sides of the insulation, if you are using insulation like fiberglass, or something that will pass moisture. That will invite condensation and rot, mold, and whatever other bad things can grow there.

If the insulation is a moisture barrier/water proof, then gluing the vapor barrier/reflective surface on both sides should not be a problem, because the moisture won't pass through the hard foam board insulation anyway.

Clear as mud?

STBRetired

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Posted: 06/12/18 09:52am Link  |  Quote  |  Print  |  Notify Moderator

As clear as the Mississippi at flood stage. I believe you can get closed cell foam boards at the big box stores. Don't know if you need actual Reflectix or if you could just use a heat reflective mylar film. I suppose whichever is cheaper would be the proper choice.

Only real downside to that insulation construction that comes to mind right away is leak detection. If water were to penetrate the roof, for example, it would be stopped by the reflectix/foam/reflectix sandwich but would eventually fill the outer air space and proceed to do its dastardly deeds to your structure. How to deal with that issue is a question. Maybe it would be better to forego the air gap on the outside and put the sandwich in intimate contact with the outer surface.


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fulltimin

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Posted: 06/12/18 10:06am Link  |  Quote  |  Print  |  Notify Moderator

STBRetired wrote:

Only real downside to that insulation construction that comes to mind right away is leak detection. If water were to penetrate the roof, for example, it would be stopped by the reflectix/foam/reflectix sandwich but would eventually fill the outer air space and proceed to do its dastardly deeds to your structure. How to deal with that issue is a question. Maybe it would be better to forego the air gap on the outside and put the sandwich in intimate contact with the outer surface.


If you think about it, that is the situation that exists now with many an rv, without the reflective coating. We have fiberglass glued to plywood, glued to foam board, glued to paneling inside. When water does get in between the outer shell (fiberglass) and the foam board, it makes the plywood wet, and has no real good way of drying out, which is what causes rot, and delamination.

When I was suggesting an air space on the outside of the shell, I was thinking of a "ventilated" air space, not a closed air space. That would allow moisture a way out and it could dry out.

Even clearer mud?

STBRetired

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Posted: 06/12/18 02:47pm Link  |  Quote  |  Print  |  Notify Moderator

Sort of a Catch 22, I guess. Mine is old enough to have fiberglass insulation instead of foam board so mine will telegraph a roof leak pretty quickly. Getting that air space ventilated without allowing water in will be the challenge. How "bendy" is Azdel? Then you would not need to worry about delamination. But I bet that stuff is really pricey.

You coat everything with POR 15 and you will probably never have a leak to begin with.

fulltimin

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Posted: 06/12/18 08:34pm Link  |  Quote  |  Print  |  Notify Moderator

STBRetired wrote:

Sort of a Catch 22, I guess. Mine is old enough to have fiberglass insulation instead of foam board so mine will telegraph a roof leak pretty quickly. Getting that air space ventilated without allowing water in will be the challenge. How "bendy" is Azdel? Then you would not need to worry about delamination. But I bet that stuff is really pricey.

You coat everything with POR 15 and you will probably never have a leak to begin with.



Yea, I've been thinking the same thing. In that case, I need to order more Por 15. Lol.

fulltimin

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Posted: 06/12/18 08:37pm Link  |  Quote  |  Print  |  Notify Moderator

Here is another pic of the Mci 5c with a double roof.



[image]

fulltimin

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Posted: 06/12/18 08:43pm Link  |  Quote  |  Print  |  Notify Moderator

And here is a slightly closer shot of the double roof. Looking closely at the 2 arrows, we can see where the roof seems to be attached to the top of the main roof.

Taking a guess, there are probably about 5 of those attachment points from one side to the other, and the entire length. Plenty of holes to allow air to get in and out.

I'm not sure how to keep birds, and other critters from getting in there, unless the extra heat in between the 2, is sufficient enough to keep all but the most hardy ones out.

Just like anywhere else, a heat shield goes a long way to cut down on heat transfer.



[image]

fulltimin

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Posted: 06/12/18 08:52pm Link  |  Quote  |  Print  |  Notify Moderator

I think and have said before, that caulk should never be the first line of defense for keeping water out. If manufacturers were required to build an rv and were prohibited from using caulk or other sealants to keep it from leaking, they would surely be built differently than they are now.

Then again, they would also cost more. Exactly how much, is anybody's guess.

There are a lot of talented engineers out there and if they were forced to come up with new ideas, I'm sure we would see some creative thinking come into play. Thinking outside the box, can be a good thing. Maybe?

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