Quote:
Originally Posted by haz.matt.1960
Are we more concerned about the marginal heat loss/cold incursion via ribs that are snugly surrounded by insulation, or condensate collection in an enclosed medium that can encourage the propagation of potentially toxic mold, & metal oxidation?
I frankly don't see more than some minor annoyance condensation from the screw heads. If the interior is heated, the cold will be driven towards the roof as temperatures shift towards equilibrium, effecting negation of the condensation situation.
(I suppose there may be suitable connectors that are less thermally conductive, if dealing with a few drips proves a problem.
(And I'm not acting as an advocate for that condition simply because I can be a drip, too)
The bridge will still be there, however conduction will be isolated to the ribs' walls. Since the open void within no longer acts as thermal variant reservoir, it ought make for a more rapid, and considerably narrower, thermal bridge profile.
While I don't specialize in bio-haz, if mold is a common problem in converted buses, I, for one, prefer facing some minor temperature vagaries over breathing in an enclosed, toxic atmosphere.
An ounce of prevention is worth the pound of cure(d foam).
Just sayin'
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Fly slow. Stay low.
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Your arguments here don't negate mine, they extend them.
We insulate to prevent heat transfer. My whole point was that current methods have some flaws. Whether they are major or minor is something you find out in use, and the way you use an RV affects how minor or serious the problem is.
That said, the only real way to address your suggestion would be to insulate directly below the ceiling in an unbroken sheet, and leave the void above empty, but ventilated.
Mold is an issue in school buses, but it only seems to be an problem in the roof where the seal has broken and moisture allowed to collect. We have all seen video of mouldy batts pulled from ceilings, mainly around hatch exits. We have also seen perfectly clean batts pulled from 20-year-old roofs. I guess the answer to that is to seal the exterior and interior correctly, which most folk seem to manage pretty well. Spray foam is good here because moisture can't collect.