Greetings, you can build an even more efficient wall( and ceiling) by using 2x4 studs with type three radiant barrier (RB) (fifoil.com) between studs, type two RB over inside surface of studs, steel 1/2" dry wall furring strips Across the studs, drywall.
Even on hottest days the Btu figures at about 2btu/hr/sf/
Plus you have better humidity levels in the hous since RB do not cause condensation.
Cellulose holds much more moisture than other types of insulation. In fact the effects of moisture can increase heat transfer to a point where it is less effective than FG.
HERE IS AN ARTICLE i WROTE SOME TIME AGO ABOUT INSULATION PERFORMANCE.
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MicrosoftInternetExplorer4
George Himmeger 224 SOUTH St TROY, IL 62294 CELL
618 698 8393 HM 618 667 4222 e-m [email protected]
Information and opinions by
George Himmeger : The chart data enclosed is taken from a mechanical
engineering handbook along with
opinions from thirty years
field experience
EXPLORING THE
LEGITIMACY OF CLAIMS OF CHARACTERISTICS, TEST PROCEDURES AND “R” RATINGS FOR
THERMAL INSULATIONS USING MECHANICAL ENGINEERING HAND
BOOK DATA AND FORMULA
Fiber glass FG - Radiant Barriers RB
Confusion
about the performance of various insulation materials is not a recent
phenomenon. Some of the confusion comes
from the fact that various materials
control heat energy transfer according to the specific physical properties of
the materials and their assembly for use.
Another problem is that large manufacturers, with government
sanction, literally control the methods used to test their product and
competing products. This has been an ongoing fight for over fifty
years in this country. Some products, commonly
used here, are not allowed in other countries because of low performance and
serious health issues. The most common
testing problems are:
(1) The tests do not reflect actual “installed summer / winter conditions”,
which can reveal up to fifty percent
difference in performance compared to “accepted tests”.
(2) Most tests
favor conductivity resistance and
limit the effects of radiant energy. Most homes have about 12-15% conductive
surfaces, about 7% is convection and air spaces accounting for up to 80% radiant energy gain or loss.
(3) Some tests
do not reveal the serious performance degradation from condensation, actually storing and increasing heat flow,
and how it affects the interior humidity levels.
(4) Some tests do not reveal possible mold
and other problems.
(5) Some tests, or labeling, do not reveal the
health problems due to toxic chemicals.
This information is classified as proprietary information and given only
to the government.
(6) The tests or labels do not reveal the ratio of
material to air volume This ratio can be as low as 1% mass to 99% air
volume allowing radiant energy to travel
through like an open door, plus air infiltration. The exception to this is radiant barriers
which rely on the air space to perform efficiently. If insulation tests were performed with the
best interest of the consumer at heart, there would probably be only two
insulations available to the consumer.
(7) The other
subject ignored by the bulk insulation manufacturers is the approximate 80%
heat gain/loss in buildings through radiant heat, infrared energy. This can be
expected because most bulk insulations are only about 10 – 20% efficient in
rejecting radiant energy, compared to about 97% for radiant barriers.
(8) The “R” factor for bulk insulations are based on
the reciprocal of a “u” factor, a
conductive test ( for a material that is about 99% air spaces?). The efficiency of RBS are based on a “k”
factor. You cannot obtain a “R” value from a
“k” factor.
The
independent, non competitive, method
presented here is based on long established data of energy exchange
between two surfaces, ceiling/floor, at a given Delta T” (temperature difference
between two surfaces) and will tell you what amount of heat energy is radiated
into and out of the home summer and winter.
This method depends on no tests and incorporates the characteristics of
the insulation, building materials and the effects of any climate condition. It can be performed by anyone with a
thermometer. Conventional “R” factor
calculations cannot tell you this, due to the problems mentioned above and that
the calculations are usually for material only.
With “R” factors you can calculate for one set of condidtions and then
find out the calculations had no reference to what is actually going on in the
structure.
The common
denominator for all insulations is; what
is the temperature of the drywall and the floor it is radiating to? This “in situ” method incorporates all the
variables because the drywall
temperature determines your heating / cooling costs. You can use either Btu calculations or
temperature calculations. You can see
why the manufacturer of low efficiency insulation will not want to use this
method. The drywall emission rate, about
90%+, is used in the following chart because that is the most commonly used
material. The source of this
information, and the following chart, is from an emissivity chart and formula
of a mechanical engineering handbook. You
may not be familiar with this source of information. It is a manual of materials charts,
characteristics, formulas and numerous other factors used by engineers to
manufacture most every thing you use.
For many professional engineers it is the engineer’s “bible”.
THE HUMAN FACTOR The average person believes that the air
temperature is the dominant factor in comfort.
This might be true if it wasn’t for the energy radiating into and out of
the building with its effects. It is this energy ratio between the interior
surfaces and the surface of the body that ultimately determines the comfort
factor and energy consumption.
For maximum
energy savings you want the lowest rate of absorption and re-radiation of
energy. Lower is better. The determining factors of any insulation’s
performance are:
1
The rate of absorption and re-emittance ( radiating
) of energy. From the “bible” we see
that wood (cellulose), and glass (fiberglass) is about 90%+ efficient in absorbing and re radiating energy. Base foam materials are about 20% efficient. Aluminum foil about .03%.
2
Other than the basic material and its construction
features, moisture, either from humidity or condensations can cause substantial
energy flow. Using the ratio or 5%
increase per 1% of moisture by weight, data published by the National Bureau of
Standards shows that fiberglass and cellulose can increase energy flow about 45 / 72% due to moisture in an
uninhabited structure. Even the relative humidity can account for a dramatic
increase in energy flow. Increased
humidity levels in an inhabited structure can cause even more energy lose /
gain along with the 1,000+ btu used to convert vapor to liquid. Since radiant
barriers do not cause condensation and are superior vapor barriers, the
interior humidity levels can be lower than with other insulations.
3
The low quality of installation can also be a
detriment to the effectiveness of insulation.
The following
chart shows Btu transfer for various ceiling temperatures. Calculations for infiltration, doors and
windows are separate as they will be the same for any insulation
installed. To increase the envelope
efficiency even more, Insulation Specialists has developed a simple method of
installing RB to reduce to about 1% the conductivity surfaces of studs and
ceiling joists from the normal 12-15 % surface
area. In summer you can measure the
drywall temperature which can reach up to 110 degs on a 95 deg day with the
lower efficiency insulations and no roof shading. If the floor temperature is 75 degs the
ceiling, using temperature figures, will radiate about 99 degs/sf/hr. The
110 deg ceiling temperature is about 25 degrees hotter than a winter radiant heat system, causing the air conditioner to
run continuously to try to compensate.
Without the air conditioner the interior temperature could exceed 100
degs. If the RB is 110 degs it will
radiate about 2-3 degs /sf/hr. In a
properly designed ranch home the interior temperature, with RB, will be about
80-81 degs without air-conditioning. The humidity levels can also be lower as the
RB does not cause condensation which can be forced into the home by the high
temperatures in the structure as with some of the lower efficiency materials. Question;
if the indoor temperature can be hotter inside than outside without the
air-conditioned, how can the manufacturer claim their material is insulation?
As you use
the chart keep in mind these two questions;
1
If bulk insulations are about 99% airspaces and
radiant energy travels through space at about the speed of light, and the base
material absorbs and re-radiates the energy at about an 80-90 percent
efficiency, how can a manufacturer claim their material is an insulator? More importantly how can an “R” value be
assigned to them ?
2
If the function of a RB is to reflect energy, how
can an “R” factor be assigned to it? How can the government and the
manufacturers of bulk insulations legitimately force the use of “R” factors in
evaluating radiant barriers? More
importantly, why?
3
Why has the US Senate interfered with, at least
twice, the governments fair trade polices, including FTC regulations, when it
comes to insulations? Regulations which
would have provided for a fair playing field.
Answer: Over $100,000,000,000.00 tax revenue per year
due to the excessive use of energy.
Because of this and other reasons the
American home owners is using up to two to three times the amount of energy to
heat a cool a home than what should be used.
In summer
you can determine the temperature of your ceiling drywall by taping a
thermometer to the drywall surface.
This chart
is based on a 75 deg floor temperature. The chart can be validated by using the
emissivity data and formula from Mark’s Mechanical Engineering Handbook. FG values are for insulation between joists
and include joist heat transfer. The RB
value is for the joists surfaces covered with the RB and a furring strip to
separate the RB from the drywall. “A”
is the dry wall temperature. “B”
represents the Btu’s radiated for the FG installation. “C” represents the Btu’s radiated for the RB
installation. “D” the Btu difference
between the FG and RB.
Although
the mechanics for side walls will be slightly difference this method can be
used foe approximate comparisons.
Summer Winter
“A” “B” “C” “D”
“A” “B”
“C” “D” 150 88 5 83 75
0 0
0
140 75 4 71 70
5 .3
5
130 61 3 58 60
14 1
13
120 49 3 48 50
22 1 21
110 37 2 35 40
31 2
29
100 26 1 25 30
38 2 36
90 15 1 14 20 45 3 42
80 5
.3
5 10
52 3 49
75
0 0 0 0 58 3 55
The 110 deg
is high lighted to represent a 95 deg day.
The 30 line is highlighted to show the similarities of the summer winter
conditions. Note the jump when the
temperature gets down to zero degs. Because
of the rapid drop off in FG efficiency as the material thickness is increased it
is difficult to extrapolate the RB and FG data for “R” value comparison. Compared to the advertised “R” value for
FG the RB “R” factor could exceed “R”100 value by a considerable amount, and it is
impossible to have a “R” value of 100
much less 100 plus.
Myth:
Dust adversely affects the RB performance. A: Dust has little or no effect on a
horizontally installed RB with airspace both sides. The top surface could be painted black and
the bottom surface might emit 1 or 2 extra Btus. Most ceiling installations have one or more
layers, so any increase in heat flow is doubtful. There is little or no dust on vertical
installations. Even with dust present the RB is superior to other materials. These comments never reveal the test material
type or test method or actual performance differences.
Myth:
Holes adversely affect the RB performance. A: Some RBs are manufactured with vapor escape holes. I know of no laboratory tests showing an
increase in heat flow, particularly in multi layer installations. Obviously you don’t want large holes, these
should be repaired.
Myth:
RBs are not as efficient on up heat (winter) as summer. A: The engineering handbook does not make such a
distinction. The mechanics of up heat vs
down conductive heat flow are different; therefore any given material may
exhibit slight differences for winter. However
these comments never note that the RB is still superior to other materials.
Myth:
Aluminum corrodes. A:
Pure aluminum, such as the 99.9% pure foil used in RB, does not corrode under normal
atmospheric conditions.
A light, invisible,
oxidation does occur preventing any further oxidation. You would not want to
breathe the fumes that could cause severe corrosion. Corrosion can and does occur in some unfinished alloy aluminum because of
the dissimilar metals used for alloying the metal.
Myth:
RB loses its insulation values over time. A: Since RBs do not corrode, the answer is self
evident. I know of installations over 30
years old that work just fine.
Myth: You can’t use
RB in very cold climates: A When Perry and other scientists went to the
poles they use aluminum foil to insulate the structures. The Navy SEALS used multi-layer
foil (mfg’d to mil spec HH I 1252) in
1964 in the Artic buildings where the mineral wool was failing. RB are used quite extensively and
exclusively, in severely cold conditions, such as, cryogenics and space
platforms.
Myth:
RB are not very efficient in attic add-on application. If the application is not proper then this is
a true statement. However, the retrofit
tests so far conducted are not the most effect application method. I have found that a double layer installation
directly over the existing material can reduce a/c run time 50% or more. Why test the most inefficient method?