METHODS
UNDERSTANDING

SUPER THERM
Vs.
FIBERGLASS

Ceramic reaction to heat

HEAT TRANSFER TRAINING CLASS

In describing insulation effectiveness of building materials such as fiberglass, we often encounter words like Conductivity, Conductance and Transmittance. Quite often, these words are mistaken and mixed up with words like R-value, K-value, or Lambda value. As a consequence, a correct assessment of insulation effectiveness can not be made. This often leads to unnecessary confusion among field operators.

Heat Transfer mechanism inside Fiberglass

Fiberglass is an ‘air trapper’. The air is "trapped" in a great many small chambers called "cells". While each cell sets up its own convection current, heat transfer is reduced in direct proportion to the size of the cell. The smaller the cell, the greater the reduction in convection. The air inside each cell reacts together when one side of the containment chamber is heated. The air sets up an active circulation. The heated air rises and the cold air falls. This circulation constantly exposes the colder air to the warm wall, thus increasing the temperature gradient (delta-T) across that wall and greatly increases the rate of heat transfer through the chamber. As it is impossible to individually study the heat transfer in cell, most heat transfer study for fiberglass is conducted experimentally using average quantity of temperature levels and heat transfer rates. The measured values of heat transfer often reflect the properties of air rather than that of fiberglass itself.

What is R-Value?

Part of the confusion in dealing with insulation material comes from so-called ‘R-Value’. The R-value concept started with this electric wire analogy. The electric resistance (Ohm), voltage drop (Volt), and current (Ampere) corresponds to thermal resistance (R-Value), temperature drop (°F), and heat flux (Btu/hr) respectively. The smaller and the longer an electric wire, the higher its electric resistance. In the same way, the narrower and the thicker an insulation material, the higher the R-Value.

This R-Value concept was adopted specifically for the fiberglass material which Owens Corning Fiberglass Corporation developed in the middle of 70's. R-value is simply defined as the ability of a material to resist heat when it is transferred from the hot side to the cold side. Technically, it is defined as the amount of temperature drop (°F) per unit heat transfer rate (Btu/hr). For convenience, however, R-Value is often expressed as the inverse of the rate of heat transfer (Btu/hr) per unit temperature (°F).

The R-Value definition can be expressed as following:

R = 1/(kA/d)

Since U=k/d, the R-Value can also be expressed as

R= 1/(UA)

If the we consider a unit cross-sectional are, A=1 sq.ft, then,

R=1/U

where
R: R-Value (°F hr/Btu)
k: Thermal conductivity (Btu inch/hr sq.ft °F)
A: Cross-sectional area (sq.ft) (perpendicular to the heat transfer direction)
d: Insulation thickness (inch)
U: Thermal Conductance (Btu/hr sq.ft °F)

Please note that the following terms are all identical:

Thermal Conductance = U-value = K-value = Transmittance

The above terms are all associated with heat conduction through a material. If heat convection is included in a calculation in addition to heat conduction, we use the term Heat Transfer Coefficient (h). It has the same unit as above. Heat convection is a surface phenomena and associated with heating or cooling of the surface of a material by blowing air in general.

Note that, if Thermal Conductance (U), or any of the above, is divided by thickness (d), you have Thermal Conductivity (k).

Thermal Conductivity, k, is the measurement of the speed at which heat travels through a material by conduction. More specifically, it is the number of BTUs of heat which will travel through one sq. foot of material which is one inch thick when there is one degree of temperature difference across the material (ie. Delta T). Thermal Conductivity is a materials inherent property and does not change with material thickness.

Thermal Conductance, U, on the other hand, is same as Thermal Conductivity, k, except that it is thickness-dependent. What it means is that, for a given material, Thermal Conductance is different for different thicknesses for the same material, As an example, let's say, a 6-inch fiberglass material has R-value of 19 (°F hr/Btu). Then,

where

R=19 (°F hr/Btu)
UA=1/R=1/19 (°F hr/Btu)=0.0526 (Btu/hr°F)
For A=1 sq.ft (cross area), U=0.0526(Btu/hr°F)/1(sq.ft)=0.053(Btu/hr sq.ft °F)
For d=6 inches (thickness),
k= Ud=0.0526 (Btu/hr sq.ft °F) x 6 (inches) = 0.316 (Btu inch/hr sq.ft °F)

For this given Thermal Conductivity, k, we can back-calculate Thermal Conductance, U, and R-Value, R, for any thickness. As an example, for 12” fiberglass, we get the following:

where

k= Ud=0.0526 (Btu/hr sq.ft °F) x 6 (inches) = 0.316 (Btu inch/hr sq.ft °F)
U=k/d=0.316 (Btu inch/hr sq.ft °F) / 12 (inches) = 0.026 (Btu/hr sq.ft °F)
For A=1 sq.ft (cross area), UA=0.026 (Btu/hr sq.ft °F) x 1(sq.ft)=0.026(Btu/hr °F)
R = 1/(UA) = 1 / 0.026(Btu/hr °F) = 38 (°F hr/Btu)

This illustration clearly shows that while Thermal Conductivity does not change with thickness, R-Value is directly proportional to insulation thickness and Thermal Conductance is inversely proportional to insulation thickness. If insulation thickness increases two fold from its original value, its R-Value increases two fold and Thermal Conductance decreases to one half from its original value.

Why Fiberglass can not have a Fixed Material Property?

When we say property, we usually have a fixed property in mind. By definition, the property may change slightly with temperature or pressure but not with the size. As they say, size shouldn't matter for property.

Then why don't we use Thermal Conductivity instead of R-value for fiberglass? Unfortunately, fiberglass can not have a fixed property such as Thermal Conductivity. This is because fiberglass is nothing but a flexible ‘air trapper’. Essentially its property is air property. Air is a very good insulator. The more air volume a fiberglass retains within, the higher its R-Value.

During fiberglass installation, however, the fiberglass wrapper gets torn and allows the outside air and moisture to migrate into the fiberglass wool pack. A small amount of moisture or externally induced air pocket can cut down fiberglass’ R-value by more than 50% easily. When the fiberglass is squashed and loses its air, its R-Value diminishes significantly. When it is exposed to wind, its value also changes drastically.

The fiberglass wrapper itself also affects R-value. Its function is to protect fiberglass and maintain it at a certain thickness. Not only does its thickness vary depending on how it is squashed or pulled, the wrapper material itself affects the R-value significantly. Foils can not be used as a wrapper material. If it is used to reflect radiation, all heat reaching the foil barrier is conductive and passes straight through making the barrier useless. If R-value measurement is made including the fiberglass wrapper, the wrapper thermal properties, thickness, and how it bonds with fiberglass all affect the results.

Comparison of SUPERTHERM and Fiberglass

Fiberglass and SUPER THERM should not be compared for R-Value for any practical purposes especially because of R-Value's thickness dependence. As an example, one coat of SUPER THERM insulation is 0.01 inch (10 mil) thick. Compare this with one layer of fiberglass of 6 inches (6,000 mils). Fiberglass's R-value is 600 times more than SUPER THERM independent of insulation property simply because of the way R-value was defined. This is like comparing apples with oranges.

Fiberglass was developed for Conduction only. In real life, all heat transfer phenomena takes place by Conduction, Convection, and Radiation. Without taking all these three heat transfer modes into account, a realistic comparison of insulation effectiveness can not be made for any material.

Radiation is a surface heat transfer mechanism like convection. But radiation works in a very different way because the heat transfer is made as the fourth power of temperature. What this means is that the magnitude of heat transferred by radiation is much higher than that transferred by convection or conduction especially when the temperature level of the heat source is high. However, most insulation material such as fiberglass is designed only for conduction.

The real issue in dealing with building insulation is to prevent ambient heat entering into or leaving a building. Once the heat enters the substrate, various building materials like fiberglass reduce the rate of heat transfer. This heat is not prevented from entering into or leaving a building – it is simply ‘slowed down’ so to speak. Thermal Conductivity is simply a measure of a material's ability that determines the rate of heat being transferred across the material. A high or low thermal conductivity of a material simply makes the heat transferred faster or slower. But, at the steady state in the real world, the total amount of heat transferred is eventually the same no matter what the conductivity value is. It is literally a matter of ‘time’ when this steady state is reached.

Preventing heat from entering into the substrate is clearly a much more effective solution that allowing the heat to enter into a substrate and then trying to slow the heat transfer rate down. SUPERTHERM was designed to ‘prevent’ heat entering into a substrate. This is accomplished by SUPER THERM repelling more than 95% of incident radiant heat. When 95% of heat input into a substrate is blocked and only less than 5% of heat is allowed to enter into a substrate, the overall benefits from different material insulation properties for this 5% are trivial.
SUPERTHERM works as the most effective radiation reflector to prevent heat entering into a substrate. Fiberglass works as an insulator to slow down the heat transfer rate ‘after’ the radiation heat enters into the substrate. If radiation is included in R-Value calculation (although doing so may not serve the purpose correctly), SUPER THERM's R-value equivalence would go up 'significantly' because radiation heat transfer increases by 4-th power of temperature difference. Then we will be able to say that one coat of SUPERTHERM can be equivalent or even exceed 6-8 inches of fiberglass batt insulation.

Conversion between British and Metric Units

There has been confusion between British units and Metric units in dealing with insulation properties. . The following table shows conversion factor when British units are converted into Metric units.

Note (1): 1 (kilo-calorie/hr) is 3.9657 Btu/hr, or 0.0011622 KW.

Note (2): The R-Value conversion unit 0.526 is based on 1 sq.ft area. Use the conversion unit 5.66 to get Metric R-Value based on 1 sq.m unit area directly from British R-Value. (1 sq.m. = 10.76 sq.ft)

(Example) 6” Fiberglass Properties in British & Metric Units

Note: The R-Value 36 (°K/W) is based 1 sq.ft area. The R-Value 3.36 (°K/W) is based 1 sq.meter area.

Thermal Conductivity in Metric Units is Lambda Value.

Please note that the actual number for R value is totally different depending on which units are used. It must be defined with units. As far as the units are consistent, it really doesn’t matter which definition we use. If one wants to see whether people who use these words actually mean the same thing, you can check the units and see whether they are consistent. The same goes for K-value or ? (Lambda) value. If units are converted from British to metric units, we can easily see that it is the same thing.

Defeating R-Value based Building Insulation Assessment

For heat transfer in buildings, there are basically three heat transfer mechanisms involved.

Radiation (Reflectivity)
This is the most dominant heat transfer mechanism. In this case, repelling heat is the most effective way to prevent the heat coming into or leaving a building. If 100% of heat were repelled, there is no heat transfer taking place, which means a perfect insulation. SUPER THERM repels better than 95% of heat.

Conduction (Thermal Conductivity)
This is the main heat transfer mechanism after part of heat is absorbed by a substrate. The heat transfer takes place through the enclosing walls. In this case, a good insulation material is one with the lowest Thermal Conductivity. Fiberglass is an air trapper and air has a low Thermal Conductivity. R-Value applies only to Thermal Conduction.

Convection (Heat Transfer Coefficient)
This is the main heat transfer mechanism after part of the heat penetrates through the building walls. The heat is now transferred into the interior of a building by indoor air current movement. This has little to do with any insulation material properties.

It is obvious that it is most effective to ‘prevent’ incident heat entering into a substrate to begin with than allowing the heat to enter into a substrate and then use a super insulation material to ‘slow down’ the heat entering inside or leaving a building. What I mean by ‘slowing-down’ is the time rate, i.e. the entire heat enters into or leaves a building no matter what but at different time rate for different insulation material. Fiberglass never prevents heat entering into or leaving a building. SUPERTHERM does. Therefore SUPER THERM is a true and much more effective insulator than Fiberglass.

Defeating Fiberglass Claims

Then why do we see so many people who are tangled up with the idea of R-Value of Fiberglass?
This perception is based on a deep-seated blind acceptance of the 1970's fiberglass general concept of how insulation works. These rules of insulation principles developed by Owens Corning are seriously limited as they do not take into account the contribution of radiation, which is the most significant component of heat transfer for insulation for buildings.

Most all insulation guidelines are currently built on fiberglass claims and calculations. These claims are short sighted, disputed and can easily be shown invalid. This, of course, leaves the engineering and architectural groups with a responsibility for determining true and accurate numbers to be used for quotations on insulation requirements for buildings and facilities nationwide and worldwide under their review.

As an example, ASTM R-test was designed by a committee to give us measurement values that hopefully would be meaningful. However, the test does not account for air movement (wind) or any amount of moisture (water vapor). In other words, the test used to create the R-value is a test in non-real-world conditions. If a fiberglass is assigned an R-value of 3.5, it can achieve this R-value if tested in an absolute zero wind and zero moisture environments. And zero wind and zero moisture are not the real-world.

Why SUPERTHERM ?

Totally repel radiation
SUPER THERM is most effective when coated on roofs and ceilings. It repels more than 95% of radiation to begin with. This ability alone is sufficient to beat fiberglass as the most effective heat barrier. Therefore debating the effectiveness of conduction heat transfer with R-value for the remaining 5% of energy input into or out of a building is not practical. Besides, R-value comparison without taking real-world conditions into account is totally meaningless. In addition although UV radiation only contributes 3% of the exterior heat load; it is the primary contributor to roofing failure. SUPERTHERM blocks better than 99% of UV radiation.

Prevent air penetration, free water, and moisture
In a nut shell, it is very likely that insulating the roof can handle more than half of the insulation needs for the entire building. This is because the primary heat transfer in nature always takes place vertically, i.e. hot air goes up and cold air comes down. Therefore roofing insulation is much more effective than sidewall insulation. By applying SUPER THERM on top of roofs and, if necessary, in the attic, and on the ceiling, air penetration can be stopped, free water can be blocked, and moisture migration can be prevented.

Corrosion Protection
SUPERTHERM will not allow corrosion to develop under it. The ceramics bond tight to the substrate surface preventing the passage of moisture, air and atmospheric conditions to affect the surface. In all fiberglass wrapped pipes found in industrial or petrochemical plants, the pipes are all corroded when the fiberglass is removed. Fiberglass breaths the air, moisture and conditions into the air pockets and holds this mixture causing the surface of the pipes walls, etc. to become corroded in a short amount of time. From industry testing, 1.5% of moisture in fiberglass will kill 35% of its effectiveness. 1.5% is breathing on it. Most climates range from 40% to 80% humidity and given it's ability to absorb this moisture, the fiberglass is worthless in a matter of days.

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Evaluation of Hot Box Test & TPRL’s Thermal Conductivity Test

TEST #1
For BTU and K value of heat flow through a wall unit:

“ASTM C-236 Standard Test Method for Steady-State Thermal Performance of Building Assemblies by Means of a Guarded Hot Box
This test was requested by Bombardier Transportation and Engineering Group. Testing performed by VTEC Laboratory, Inc. and National Certified Testing Laboratories. This test is used to establish R value for fiberglass and other batt materials as determined from these results. Control is the fiberglass test density board of 3 inch thickness. Result of applying SUPER THERM over the standard fiberglass test density board. Thermal Conductivity, ke, was measured.

3 inch high-density fiberglass board tested: k = 0.52 (Btu inch/hr sq.ft °F); R=5.77 (hr/Btu inch)

• 10 mils of SUPERTHERM tested: ke = 0.31(Btu inch/hr sq.ft °F) ; RE=9.7 (hr/BTU inch)
One coat on heat source side of board. This implies that SuperTherm helps prevent radiation from the heat side (heat source), thus making 40% improvement.

• 20 mils SUPERTHERM tested: ke = 0.21(Btu inch/hr sq.ft °F) ; RE= 14.3 (hr/BTU inch)
One coat on each side of board (heat source and cold side) total of 2 coats or 20 mils. This implies that SUPER THERM helps prevent radiation heat from hot side (heat source) and from convection from cold side, thus making 60% improvement.

Note: k: Thermal Conductivity; ke: Equivalent Thermal Conductivity

Note: R-value is defined as R=d/kA. For 3” thickness (d) and 1 sq.ft. cross-sectional area (A), the fiberglass board has R=5.77 (hr/Btu inch) as shown above. Now as SUPERTHERM coating adds almost no thickness (0.01 & 0.02 inches) and SUPER THERM conductivity is more than 10 times of Fiberglass, the only major contribution of SUPERTHERM to cutting down the heat flow in above test is by blocking radiation and convection. Therefore we can safely conclude that the conductivity of SUPER THERM-coated fiberglass board above is actually an Equivalent Conductivity (radiation effect included in the conductivity). The Equivalent R-Value (RE) above was obtained by the same definition: RE=d/keA where d is thickness (inches), ke is Equivalent Thermal conductivity (Btu inch/hr sq.ft °F), and A is cross-sectional are (ft2).

TEST #2
BTU conduction test to determine the BTU conduction block performance for SUPERTHERM.

ASTM E-1461-92 Thermal Diffusivity
ASTM E-1269 Specific Heat

BTU value measurement testing of SUPER THERM alone as a single coating film at 100 C or 212 F. Metal Plate was tested without the coating to allow 367.20 BTU/sq.ft./hour/F to Pass through. SUPERTHERM was tested in one coat at 14.9 mils over the metal plate and allowed 3.99 BTU/sq.ft. /hour/F (this is U-Value) to pass through. ASTM E 1269 Specific Heat and ASTM E-1461-92 Thermal Diffusivity used to find these results.

This test was done to calculate Thermal Conductivity from:
Thermal Conductivity = Thermal Diffusivity x Density x Specific Heat.
The heat input and output values have nothing to do with the standard steady state 1-D conduction test as this test was conducted to get property values when temperature rises with time (unsteady state). SUPER THERM Conductivity calculated in this test is in the range 3.77-4.51 (Btu inch/hr sq.ft °F) for various thicknesses. Please note that Thermal Conductivity is independent of thickness but slightly dependent on temperature and mass. The deviations of conductivity values are associated with these dependencies.

Summary

The 1997 TPRL Report that shows ASTM E-146 & 1269 Test was conducted to get SUPERTHERM's Thermal Conductivity by using Flash Method. This method is totally different from Steady-State Method we are familiar with.

In Steady-State Method, we used a device such as a guarded hot box. In this case, the temperature does not change with time so we call it a steady-state method. Thermal Conductivity or R-Value may be calculated from this kind of test.

In Flash Method, an instant laser energy input is given and the consequent temperature rise in time is measured to determine Thermal Diffusivity and Thermal Conductivity. The heat flux value used in Flash Method can NOT be used to calculate Thermal Conductivity or R-Value using the traditional energy balance method.

The following summarizes two cases where SUPER THERM's Thermal Conductivity can be looked at from two different aspects. The 3 columns represent Thermal Conductivity in 3 different units.

Note: k: Thermal Conductivity; ke: Equivalent Thermal Conductivity

The values in these tables indicate that:

1. Test 1 shows SUPER THERM's ‘Effective” Thermal Conductivity. These thermal conductivity values were obtained in engineering-controlled test environment.

2. Test 2 gives SUPER THERM's “Actual” Thermal Conductivity. These thermal conductivity values were obtained in a scientifically-controlled test environment.

3. At any rate, given these values, please note that 10-mil thickness is the same as 6" fiberglass in Thermal Conductivity.

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