Skip, rusty is a temperature measurer NOT a design engineer. If rusty were
correct, all that pink insulation you see in Home Cheapo would not have the
shiny foil backing it does. Maybe rusty has never seen insulation in HD or any
place else?

Rusty, thank you so much for your informed and concise presentation. It's
very complete, and answers most of my questions, but generates a couple of
others. Please indulge me? And, since you're spamtrapped, I can't ask you
directly, but may I quote you in the various mailing lists to which I posed
the same question(s)?

A reflective barrier can greatly reduce the heat gain to a cool object
from
infrared radiation. The question is, where to put it?

(exposition clipped)

The bottom line: Most heat gain to a refrigerated box is through
convection
and conduction, not infrared radiation. There is no free ride and
reflective
foils will not noticeably improve the insulating qualities of the typical
boat ice box.

So, effectively, without a vacuum (or, at least, a free-space non-touching
environment), the addtion of aluminum foil merely acts to accelerate
(aluminum being an excellent heat conductor) heat transfer?

Thus, for example, the foil-faced building insulation products are no better
than the level of vacuum behind them?

I'd been migrating to the thought of layering heavy foil between the highest
R-value foam I could find, and then doing a heat-sealed vapor barrier wrap,
evacuated to the best of my ability. However, your comments suggest that's
a waste of time.

I *think* I understand you to say that foil is counterproductive if not
faced with a vacuum. If so, from that, if I'm not going to spring for the
vacuum panels, simple block foam, encapsulated to prevent moisture, is the
best?

My box exterior (which is a single layer of roving over the hard urethane
2") is currently exposed for most of two sides. I'd thought to put foil on
that exterior surface. If I understand you properly, that's
counterproductive?

On to the last:

I can think of one place a reflective foil might help. If you had a
freezer
or refrigerator, with adequate vacuum or foam insulation, that had one
side
facing the inside of you engine room then foil on that surface facing the
engine would reduce infrared heat gain to the box when running the engine.
But that can also be covered with Mylar faced noise control foam with even
better results.

Is that like the lead foam used in noise control, nearly as expensive as
heat shield :{)) ? Or is there some other noise abatement of which I'm not
aware (there are probably encyclopediea worth of info of which I'm not
aware!)? Is this an application where a foil-backed insultion board would
help?

Thanks again for your knowledgeable input.

L8R

Skip and Lydia

Rusty O


--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

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