One of my respondents to my question about vacuum panels is very high on
"Heat Shield" (www.heatshieldmarine.com) - a mostly radiant barrier, to my
expectations, but their claim is that in conjunction with foam, it has the
effect of tripling the foam R value.

As I don't know what's inside these foil separators (1/2, 3/4 and 1 inch
material) I can't judge the insulating value of that part. However, what I
*think* I know (see Mark Twain's quotation about facts for perspective) is
that a radiant barrier can be any shiny surface - such as on the outside of
Tuff-R or other building supply foam board, or simple home aluminum foil -
including, I suppose, those Mylar "space blankets" available cheaply in
camping stores Despite their assertions that their 1" is equivalent to 5 or
6" of urethane foam, as their site seems to place a great deal of importance
on the radiant barrier, I don't know how much value to place on *their*
radiant barrier over any other. It seems to me that if this premise were
so, houses would be insulated with silver Mylar film outside instead of the
usual tyvek wrap as it seems - at least from the premise of their claims -
it would improve the thermal barrier multifold. Not being a thermal
engineer, I don't know whose claims to believe...

So, again, I'm looking for real-world experience. Anyone had an
installation of Heat Shield they'd care to comment on?

Thanks.

L8R

Skip and Lydia

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

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

For what it's worth:

I am, among other things, a "Certified Infrared Thermographer"
(Infraspection Institute). I have several years experience with using
infrared cameras to inspect electrical systems, building envelopes, and
industrial processes. In addition, I have taught these skills to others in
formal classes.

In simple terms, there are three methods of transferring heat: 1) Conduction
2) Convection 3) Radiation

1) Conduction - If two materials are touching each other heat will be
transferred from the warmer to the cooler.
2) Convection - If two materials are separated by a liquid or gas the heat
can be transferred from one material to the other through the motion of the
liquid or gas.
3) Radiation - All materials give off infrared radiation from their
surfaces. This radiation is just below the lower end of visible light and
extends down to microwave frequencies. The qualities of the surface
determine the "Emissivity" of the surface. A perfect radiator has an
emissivity of one. A perfect cold dark body has an emissivity of zero. Real
world objects are between these two extremes. Highly reflective surfaces
usually have a very low emissivity and will not radiate heat efficiently nor
absorb very much heat energy. This is why gold foil is used to cover certain
areas of satellites. It protects them from the suns infrared radiation.

It's also why the space shuttle must roll over with it's top facing earth
and it's bay doors open soon after reaching orbit. It's cooling radiators
(high emissivity) are inside the cargo bay and they must be kept exposed to
the outside and facing away from the sun at all times. Since they have no
means of removing heat by conduction or convection in outer space, they must
do it by infrared radiation.

After that very simplified beginning, on to reflective barriers.

A reflective barrier can greatly reduce the heat gain to a cool object from
infrared radiation. The question is, where to put it? If you have an
insulated ice box you could put it on the outside surface. It would then
reduce heat gain from infrared radiation. However, it would do nothing to
reduce heat gain from convection. The warm air surrounding the outside of
the box would transfer heat to, and through, the reflective surface just as
if it was painted flat black. In addition, since the reflective foil was in
contact with the outside of the box, conduction would just move the heat
right into your ice box.

You could put it on the inside of the box, with the shiny side facing out.
In this case the foil would be in contact with the material forming the box
and again conduction would pass the heat right through the foil. The same
problem occurs no matter where you place the foil. Conduction or convection
always wins.

The only solution I know would be to build an inner box, cover it with shiny
foil, and surround that with a layer of vacuum to eliminate convection and
conduction. Even then, heat gain through infrared radiation would be the
least of your concerns. The closest practical solution is to use insulated
vacuum panels like those built by Glacier Bay and others. They have a real
life insulating rating of R50 per inch. But, you will pay for that luxury.

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.

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.

Rusty O


Reflective barriers
"Skip Gundlach" skipgundlach sez use my name at earthlink dot fishcatcher
(net) - with apologies for the spamtrap wrote in message
...
One of my respondents to my question about vacuum panels is very high on
"Heat Shield" (www.heatshieldmarine.com) - a mostly radiant barrier, to my
expectations, but their claim is that in conjunction with foam, it has the
effect of tripling the foam R value.

Rusty, you take measurements for a living, but are not a design eng. a couple
of things to make note of:

1.) "shiney" is shiney from both sides, as far as radiation is concerned.
shiney out or shiney in, same same.

2.) shiney on the outside does NOT make for greater (or lesser) conductivity
or convectivity. shiney on the outside makes for reflection of the radiant
heat **from the outside** (where heat is in a reefer system). shiney on the
inside means some of the radiant heat is absorbed on the way through the
insulation (makes for warmer insulation) and then is reflected back into the
insulation where some of it is also absorbed (making for even warmer
insulation).

3. You, Rusty, sound like a shill for N. Bruce Nelsen of Glacier Bay, a man who
over the years has made one hell of a lot of claims that don't stand close
examination.

4.) "vacuum" panels are not vacuum at all, but rather are panels with a plastic
latice inside (to hold the sides of the panel apart) with much, but by no
means all, of the air removed. (air pressure is 14.7 pounds PER SQUARE INCH,
so a 1 square foot panel encasing a true vacuum would have over 2,000 pounds
pressure trying to collapse the sides.

For what it's worth:

I am, among other things, a "Certified Infrared Thermographer"
(Infraspection Institute). I have several years experience with using
infrared cameras to inspect electrical systems, building envelopes, and
industrial processes. In addition, I have taught these skills to others in
formal classes.

In simple terms, there are three methods of transferring heat: 1) Conduction
2) Convection 3) Radiation

1) Conduction - If two materials are touching each other heat will be
transferred from the warmer to the cooler.
2) Convection - If two materials are separated by a liquid or gas the heat
can be transferred from one material to the other through the motion of the
liquid or gas.
3) Radiation - All materials give off infrared radiation from their
surfaces. This radiation is just below the lower end of visible light and
extends down to microwave frequencies. The qualities of the surface
determine the "Emissivity" of the surface. A perfect radiator has an
emissivity of one. A perfect cold dark body has an emissivity of zero. Real
world objects are between these two extremes. Highly reflective surfaces
usually have a very low emissivity and will not radiate heat efficiently nor
absorb very much heat energy. This is why gold foil is used to cover certain
areas of satellites. It protects them from the suns infrared radiation.

It's also why the space shuttle must roll over with it's top facing earth
and it's bay doors open soon after reaching orbit. It's cooling radiators
(high emissivity) are inside the cargo bay and they must be kept exposed to
the outside and facing away from the sun at all times. Since they have no
means of removing heat by conduction or convection in outer space, they must
do it by infrared radiation.

After that very simplified beginning, on to reflective barriers.

A reflective barrier can greatly reduce the heat gain to a cool object from
infrared radiation. The question is, where to put it? If you have an
insulated ice box you could put it on the outside surface. It would then
reduce heat gain from infrared radiation. However, it would do nothing to
reduce heat gain from convection. The warm air surrounding the outside of
the box would transfer heat to, and through, the reflective surface just as
if it was painted flat black. In addition, since the reflective foil was in
contact with the outside of the box, conduction would just move the heat
right into your ice box.

You could put it on the inside of the box, with the shiny side facing out.
In this case the foil would be in contact with the material forming the box
and again conduction would pass the heat right through the foil. The same
problem occurs no matter where you place the foil. Conduction or convection
always wins.

The only solution I know would be to build an inner box, cover it with shiny
foil, and surround that with a layer of vacuum to eliminate convection and
conduction. Even then, heat gain through infrared radiation would be the
least of your concerns. The closest practical solution is to use insulated
vacuum panels like those built by Glacier Bay and others. They have a real
life insulating rating of R50 per inch. But, you will pay for that luxury.

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.

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.

Rusty O


Reflective barriers
"Skip Gundlach" skipgundlach sez use my name at earthlink dot fishcatcher
(net) - with apologies for the spamtrap wrote in message
...
One of my respondents to my question about vacuum panels is very high on
"Heat Shield" (www.heatshieldmarine.com) - a mostly radiant barrier, to my
expectations, but their claim is that in conjunction with foam, it has the
effect of tripling the foam R value.

A-men brother.

The Heat Shield folks do a demo at boat shows where they wrap an Igloo
cooler in the stuff and compare the ice melt to a bare cooler. The problem
is they sit the coolers in the sun where 90% of the load is radiant. That
will not be the case in the galley.

One place I do plan to use a Heat Shield like product in between the head
liner and the cabin top where the load will be mostly radiant. But I will
be using that silver Mylar and bubble wrap duct insulation from Home Despot.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Rusty O" wrote in message
ink.net...
For what it's worth:

I am, among other things, a "Certified Infrared Thermographer"
(Infraspection Institute). I have several years experience with using
infrared cameras to inspect electrical systems, building envelopes, and
industrial processes. In addition, I have taught these skills to others in
formal classes.

In simple terms, there are three methods of transferring heat: 1)
Conduction
2) Convection 3) Radiation

1) Conduction - If two materials are touching each other heat will be
transferred from the warmer to the cooler.
2) Convection - If two materials are separated by a liquid or gas the heat
can be transferred from one material to the other through the motion of
the
liquid or gas.
3) Radiation - All materials give off infrared radiation from their
surfaces. This radiation is just below the lower end of visible light and
extends down to microwave frequencies. The qualities of the surface
determine the "Emissivity" of the surface. A perfect radiator has an
emissivity of one. A perfect cold dark body has an emissivity of zero.
Real
world objects are between these two extremes. Highly reflective surfaces
usually have a very low emissivity and will not radiate heat efficiently
nor
absorb very much heat energy. This is why gold foil is used to cover
certain
areas of satellites. It protects them from the suns infrared radiation.

It's also why the space shuttle must roll over with it's top facing earth
and it's bay doors open soon after reaching orbit. It's cooling radiators
(high emissivity) are inside the cargo bay and they must be kept exposed
to
the outside and facing away from the sun at all times. Since they have no
means of removing heat by conduction or convection in outer space, they
must
do it by infrared radiation.

After that very simplified beginning, on to reflective barriers.

A reflective barrier can greatly reduce the heat gain to a cool object
from
infrared radiation. The question is, where to put it? If you have an
insulated ice box you could put it on the outside surface. It would then
reduce heat gain from infrared radiation. However, it would do nothing to
reduce heat gain from convection. The warm air surrounding the outside of
the box would transfer heat to, and through, the reflective surface just
as
if it was painted flat black. In addition, since the reflective foil was
in
contact with the outside of the box, conduction would just move the heat
right into your ice box.

You could put it on the inside of the box, with the shiny side facing out.
In this case the foil would be in contact with the material forming the
box
and again conduction would pass the heat right through the foil. The same
problem occurs no matter where you place the foil. Conduction or
convection
always wins.

The only solution I know would be to build an inner box, cover it with
shiny
foil, and surround that with a layer of vacuum to eliminate convection and
conduction. Even then, heat gain through infrared radiation would be the
least of your concerns. The closest practical solution is to use insulated
vacuum panels like those built by Glacier Bay and others. They have a real
life insulating rating of R50 per inch. But, you will pay for that luxury.

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.

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.

Rusty O


Reflective barriers
"Skip Gundlach" skipgundlach sez use my name at earthlink dot fishcatcher
(net) - with apologies for the spamtrap wrote in message
...
One of my respondents to my question about vacuum panels is very high on
"Heat Shield" (www.heatshieldmarine.com) - a mostly radiant barrier, to
my
expectations, but their claim is that in conjunction with foam, it has
the
effect of tripling the foam R value.

Jax, you still don't understand the principle that it is better to keep your
mouth shut and have people think you are stupid than opening it and
confirming the fact.

Most vacuum panels are filled with Instil, an inert open celled silica based
foam board from Dow. It has a crush strength of about 50 PSI, well above
the 14.7 atmospheric pressure, and an R value at standard pressure of about
5. At 1 milibar vacuum the R value is about 25 and at .1 milibar it is
about 30. Glacier Bay uses a special reinforced aerogel material called
Nanogel made by Cabot (the Cabosil people) with an R value at standard
pressure of about 15. While the bare material is extremely delicate its
latticework structure makes it very strong under even compression. At 10
milibar the R value is about 30 and at .1 milibar it is about 50. The curve
of vacuum to R value is flatter with Nanogel than with Instil. The obvious
advantage is that as the panel loose vacuum the Nanogel will maintain more
insulation value. The disadvantage is that Nanogel is much more expensive
and harder to work with.

The problem with all vacuum insulation is that it is impossible to
maintained a high vacuum with a low conductivity flexible membrane. Air
molecules will slowly find a way in. Back in the 80s
a vacuum panel made of a stainless envelope packed with precipitated silica
was popular in refrigerated containers and some high end European
refrigerators. It was only effective in large sizes because the steel
conducted a lot of heat around the edges. In the mid 90s Toyo and Dupont
developed films consisting of several layers of various UHMW plastics coated
with a very thin layer of aluminum that made smaller panels practical and
easier to fabricate. Those films have been greatly improved over the last 5
years. Around the same time SAES introduced a room temperature getter
material to absorb stray gas molecules and packages it in small inexpensive
pucks to be inserted in the panels.

The net result is that you can reasonably expect 10 to 15 years of R values
better than 25 per inch from almost any well constructed vacuum insulation
panel. The Glacier Bay Panels will last about 30% longer and have the
distinct advangate of maintaining a reasonable level of insulation even with
no vacuum. The down side is that they are about twice as expensive.
Regardless, marine refrigerators made with vacuum insulation should be built
with the need to eventually replace the panels in mind. I am counting on 8
to 10 years and will probably replace them even if they are still reasonably
effective. At the present rate of improvement by then the technology will
be far better and the prices significantly lower.

BTW, you should NOT use two part pour in place foam to fill gaps between
vacuum panels. Two part foams produce a lot of heat as they cure. The
vacuum panels are so effective that they will trap the heat and possibly
damage the plastic film. Moisture curing spray foam like Great Stuff is a
lot safer.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"JAXAshby" wrote in message
...
Rusty, you take measurements for a living, but are not a design eng. a
couple
of things to make note of:

1.) "shiney" is shiney from both sides, as far as radiation is concerned.
shiney out or shiney in, same same.

2.) shiney on the outside does NOT make for greater (or lesser)
conductivity
or convectivity. shiney on the outside makes for reflection of the
radiant
heat **from the outside** (where heat is in a reefer system). shiney on
the
inside means some of the radiant heat is absorbed on the way through the
insulation (makes for warmer insulation) and then is reflected back into
the
insulation where some of it is also absorbed (making for even warmer
insulation).

3. You, Rusty, sound like a shill for N. Bruce Nelsen of Glacier Bay, a
man who
over the years has made one hell of a lot of claims that don't stand close
examination.

4.) "vacuum" panels are not vacuum at all, but rather are panels with a
plastic
latice inside (to hold the sides of the panel apart) with much, but by no
means all, of the air removed. (air pressure is 14.7 pounds PER SQUARE
INCH,
so a 1 square foot panel encasing a true vacuum would have over 2,000
pounds
pressure trying to collapse the sides.

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

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

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?

That is correct. It is opencell foam either side of a rubber membrane
imbedded with lead and a foil face. I don't think you really have that
option though. You would have to rip everything off that front engine room
wall and having seen it I do not believe you really want to do that. :-)

A little clarification: Once the radiant energy is absorbed it becomes
conductive and the metal actually speeds up transmission. If the foil is
behind another layer that absorbs radiant energy, like the wood face of the
refrigerator it looses much of its effectiveness because the radiant energy
has already been converted to conductive. The foil side on foam or
fiberglass insulation goes on the warm side. It reflects some of the
remaining radiant load but mostly it acts as a moisture barrier.

With your galley layout you have two places where the fridge will be subject
to radiant load. The side of the stove where it sits beside the outboard
end of the box and the back side against the engine room. You are cutting
down the size of the box (Seriously folks, this box is big enough to fit two
coffins in.) so if you go with vacuum insulation you might consider turning
that far end into pot storage. The front wall of the engine room might be a
good candidate for some foil insulation. (Not nessacarily Heat Shield) It
will be easier to install than SoundDown and sound insulation is useless
unless you completely cover all the room surfaces.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

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?

Yes, the heat would tend to conduct right through the aluminum. However,
given that the materials on each side would tend to have lower levels of
conduction, the aluminum probably has no effect either way. In other words,
if you sandwiched a layer of foil between two layers of insulation, the
overall conduction would be nearly the same as the insulation layers alone.

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

I'm not sure what the advantage of foil-faced foam board is over non-faced
foam board in housing applications. I have a call in to my brother who is a
building materials guru. I will pass on the information when I hear from
him.

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.

Yes, I believe that would be a waste of time. My hot tub cover had a heat
sealed vapor barrier around the foam insulation. After a few years it got so
heavy from trapped moisture, I had to replace it. And, that was after
unwrapping it and letting it dry in the sun for three months.

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?

Yes, the foam is then the best way.

Some other thoughts:
1) Wet insulation is an excellent heat conductor
2) When insulation gets wet, it can be almost impossible to dry out.
3) It's almost impossible to totally encapsulate the insulation around a
boat ice box.
4) Imperfections will allow air to move in and out of the insulation.
5) When the air is cool and dense it will migrate into the insulation.
6) When the air is warmed it will expand, release its moisture, and move
out.
7) After enough cycles of cooling and warming, the insulation will be wet
from the released moisture.

This is why you have a vapor barrier in your house between the interior and
the insulation, but not on the outside.

These problems can be minimized by not trying to encapsulate the insulation.
Give it a way to dry out between cycles. Also, try to use closed cell foam
instead of open cell. You can test your insulation before installing it buy
breaking off a small piece, carefully weigh it, put it in a glass of water
for a few days, take it out and weigh it again. If there's no appreciable
weight gain, it should work okay on your boat.

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?

Unless the exterior is exposed to a strong radiant heat source, the foil
won't help.

On to the last:
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?

Yes, it's like the lead & foam sound insulation. I'm using a sound blocking
product with a back layer of foam, a layer of some type of semi-rigid
plastic, a thicker layer of foam , and faced with shiny Mylar. About an
inch and a quarter overall thicknes. I don't remember the brand name but the
price was not out of line. My local rubber products retailer carries it in
stock.

Foil faced insulation in an engine room would work to keep radiant and
convected heat away from living spaces. But shiny-faced sound control
products with their 'decoupled' layer would do a better overall job.

Low emissivity surfaces are very effective at minimizing heat gain from
non-contact radiant sources. This includes the sun or even a hot engine
block. They are not a solution to other problems.

Rusty O

Thanks again for your knowledgeable input.

L8R

Skip and Lydia

I talked with my brother about the different types or foam board.

The non-faced insulation boards, colored pink, blue, or green, are extruded
polystyrene. Because of the nature of the extrusion process the boards have
enough structural strength to be handled, cut, and installed without any
additional coverings. (The color tells you who made it.)

The foil-faced yellow looking foam boards are (poured) expanded
polyisocyanurate. The facings applied to these boards are there to provide
structural strength during the manufacturing, handling & installation
processes. Otherwise they would tend to just break apart at random
locations. (It's natural yellow color is difficult to dye to any other
color.)

White styrofoam board is also available.

He also mentioned the foil faced air bubble plastic material. He said the
manufactuers of this product have not been able to prove that it has any
real 'R' value of any kind. The salesmen even suggested a good use would be
to stuff it in your shoes to keep your feet dry. He refuses to distribute
this product for these reasons.

Rusty O

Glen, I was trying to say that $1,000 a square foot "vacuum" panels don't stand
up to close scientific scrutny. Buy 'em as is your wish.

btw, have you checked just how much cooling power is required to chill a air
temp six-pack or two as compared to how much cooling power is required to
remove heat passed into the reefer from the outside. hint: the difference in
total BTU's of cooling required is almost nothing when comparing R-4 with R-8,
and is virtually nothing when comparing R-8 with R-100. It ain't the heat
going through the side that gets you, it is the heat you put into the reefer in
the form of food.

something N. Bruce Nelsen kinda neglects to make mention of.

but if you feel you want to hug P. T. Barnum, have at it.

Jax, you still don't understand the principle that it is better to keep your
mouth shut and have people think you are stupid than opening it and
confirming the fact.

Most vacuum panels are filled with Instil, an inert open celled silica based
foam board from Dow. It has a crush strength of about 50 PSI, well above
the 14.7 atmospheric pressure, and an R value at standard pressure of about
5. At 1 milibar vacuum the R value is about 25 and at .1 milibar it is
about 30. Glacier Bay uses a special reinforced aerogel material called
Nanogel made by Cabot (the Cabosil people) with an R value at standard
pressure of about 15. While the bare material is extremely delicate its
latticework structure makes it very strong under even compression. At 10
milibar the R value is about 30 and at .1 milibar it is about 50. The curve
of vacuum to R value is flatter with Nanogel than with Instil. The obvious
advantage is that as the panel loose vacuum the Nanogel will maintain more
insulation value. The disadvantage is that Nanogel is much more expensive
and harder to work with.

The problem with all vacuum insulation is that it is impossible to
maintained a high vacuum with a low conductivity flexible membrane. Air
molecules will slowly find a way in. Back in the 80s
a vacuum panel made of a stainless envelope packed with precipitated silica
was popular in refrigerated containers and some high end European
refrigerators. It was only effective in large sizes because the steel
conducted a lot of heat around the edges. In the mid 90s Toyo and Dupont
developed films consisting of several layers of various UHMW plastics coated
with a very thin layer of aluminum that made smaller panels practical and
easier to fabricate. Those films have been greatly improved over the last 5
years. Around the same time SAES introduced a room temperature getter
material to absorb stray gas molecules and packages it in small inexpensive
pucks to be inserted in the panels.

The net result is that you can reasonably expect 10 to 15 years of R values
better than 25 per inch from almost any well constructed vacuum insulation
panel. The Glacier Bay Panels will last about 30% longer and have the
distinct advangate of maintaining a reasonable level of insulation even with
no vacuum. The down side is that they are about twice as expensive.
Regardless, marine refrigerators made with vacuum insulation should be built
with the need to eventually replace the panels in mind. I am counting on 8
to 10 years and will probably replace them even if they are still reasonably
effective. At the present rate of improvement by then the technology will
be far better and the prices significantly lower.

BTW, you should NOT use two part pour in place foam to fill gaps between
vacuum panels. Two part foams produce a lot of heat as they cure. The
vacuum panels are so effective that they will trap the heat and possibly
damage the plastic film. Moisture curing spray foam like Great Stuff is a
lot safer.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"JAXAshby" wrote in message
...
Rusty, you take measurements for a living, but are not a design eng. a
couple
of things to make note of:

1.) "shiney" is shiney from both sides, as far as radiation is concerned.
shiney out or shiney in, same same.

2.) shiney on the outside does NOT make for greater (or lesser)
conductivity
or convectivity. shiney on the outside makes for reflection of the
radiant
heat **from the outside** (where heat is in a reefer system). shiney on
the
inside means some of the radiant heat is absorbed on the way through the
insulation (makes for warmer insulation) and then is reflected back into
the
insulation where some of it is also absorbed (making for even warmer
insulation).

3. You, Rusty, sound like a shill for N. Bruce Nelsen of Glacier Bay, a
man who
over the years has made one hell of a lot of claims that don't stand close
examination.

4.) "vacuum" panels are not vacuum at all, but rather are panels with a
plastic
latice inside (to hold the sides of the panel apart) with much, but by no
means all, of the air removed. (air pressure is 14.7 pounds PER SQUARE
INCH,
so a 1 square foot panel encasing a true vacuum would have over 2,000
pounds
pressure trying to collapse the sides.