Astec Engineer Guide

—————— ENGINEER'S GUIDE ——————
INTRODUCTION
The purpose of this Engineer's Guide is to present the engineering physics
associated with the energy interactions of ASTEC coatings on buildings. The heat
transfer equations, definitions, and property descriptions are intended as "review
material" for technically trained people, but the information should be comprehensible to
anyone with a college physics course background.

BACKGROUND SITUATION
Heat transfer through building roofs and walls, through petrochemical tanks, and
through other industrial structures can be very expensive, not only from an energy point of
view (i.e., cooling load cost, evaporation losses), but also from a maintenance and repair
standpoint.
Traditionally, we have attempted to manage heat after it penetrated the structure
by using construction materials with a good R-value (resistance to heat flow) and a low
K-value (conductivity). However, R-value is directly proportional to the thickness of the
construction material used, and increasing the R-value becomes unrealistic when cost
exceeds the value of the energy saved. Moreover, mass insulation such as fiberglass
wool is only effective if it is properly protected from humidity and water penetration.
Should the roof leak (and they all do at one point or another!), the mass insulation
becomes a compressed sponge with a greatly diminished R-value.
There are several factors which influence the heat transfer through a roof, a wall, a
building, or a structure in general. These include, but are not limited to, the following:

Environmental Factors, which cannot be manipulated:

• Ambient air temperature
• Solar radiation
•Wind

Building Material Factors which can be manipulated:

• Material resistivity (R-value)
• Surface solar reflectivity/absorptivity
• Surface thermal radiation emissivity

Also, the geometric structure of the building itself is important as to how much and
where heat will transfer. For instance, a 7-story building is exposed to more radiation on
its walls than on its roof. Similarly, a single story building receives 70% to 90% of its
radiation on the roof. Most industrial buildings, such as manufacturing plants, storage
areas, etc., are single story buildings with galvanized metal roofs, asbestos tile roofs,
built-up roofs (BUR), or concrete roofs. All of these construction materials absorb a high
degree of solar radiation and offer very little resistance to heat transfer.

Heat Management Rationale
In recent years, prevention has been the focus of heat management. It is more
effective and cheaper to prevent heat penetration than to deal with it once it has occurred.
This prevention approach is evident in NASA's space vehicle re-entry program where the
astronauts' capsule is protected from the atmosphere's intense heat with a ceramic tile
shield. The shield's highly reflective surface prevents heat penetration to a great extent,
and its high thermal emissivity quickly re-radiates any heat absorbed.

NASA's heat management through radiation control led to the development of
ASTEC, a ceramic liquid-applied elastomeric coating with high solar reflectivity and high
thermal emissivity. The effective use of radiation control coatings (RCC) is predicated on
two basic principles:

1. The best way to reduce heat transfer is to prevent it
from entering the building. High solar reflectivity
achieves this goal.

2. The best way to manage heat transfer is to re-emit as
quickly as possible. High thermal emissivity addresses this
issue.

The reflection and emission of radiation from a metal roof, a concrete surface, or
any other opaque material originates within a few microns of the surface; hence both
solar reflectivity1 (the fraction of solar irradiation reflected) and thermal emissivity2 (the
rate of radiation emitted by a given surface compared to a blackbody at the same
temperature) are functions of the surface state of a material rather than of its bulk
properties. For this reason, the solar reflectivity and the thermal emissivity of a coated
surface are characteristics of the coating (i.e., ASTEC) rather than that of the underlying
surface.
The measured values for ASTEC white-colored coatings are a solar reflectivity of
0.83 in the UV range, a luminous reflectivity of .90 in the visible range of the solar
spectrum, and a thermal emissivity of 0.92. ASTEC's average solar reflectivity of 0.86
means that only 14% of the incoming solar energy will be absorbed and converted to
heat energy. The surface, to keep itself cooler, will be emitting radiation at 92% the rate
of a "perfect emitter" (blackbody radiator) at the same temperature.

DEVELOPING THE MODEL
The approach taken in this guide is to develop a heat transfer model and
equations for an outside roof (or wall) structure. The model will take into account the
environmental factors of solar radiation, outside air temperature, and wind velocity, plus
specific roof/wall construction, material properties, and indoor temperature, with and
without ASTEC coating.
Conservation of Energy
The first Law of Thermodynamics is known as the law of the conservation of
energy. It stipulates that for a given system, energy is always conserved; it is never lost.

The energy balance is expressed as follows:

[Net Amount of Energy Added to System] = [Net Change in Stored Energy of
System]
Or
Energy In - Energy Out = Increase or Decrease in
Energy of System

However, this conservation of energy equation is further simplified if the system (a roof or
a wall, for instance) is already heated up. If the temperatures within the system are not
changing, then the stored energy is not changing, and the right side of the above equation
is equal to zero. This situation is called the "steady state" condition and allows us to write
the steady state conservation of energy equation as:

Energy In = Energy Out

The second Law of Thermodynamics states that heat always travels from a "hot" region to
a "colder" region. The terms "hot" and "cold" are relative terms in that an object with a
lower temperature is "colder" whereas an object with a higher temperature is "hotter".

Thermodynamics:

1. Energy is always conserved; it is never lost
a. What goes in... must come out
2. Heat always travels from a "hot" region to a "colder" region.

Therefore, the issues are:
• Flow of Heat in Buildings
• Temperatures in Buildings

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1
Solar reflectivity defines the ability to return or to bounce away incident radiation. In practice, it is the ability of a surface to
reflect all or a percentage (86% in the case of ASTEC) of incident radiation such as solar radiation. The reflectivity of a surface
is a measure of the amount of reflected radiation. However, solar reflectivity is wavelength dependent. ASTEC's solar
reflectivity ranges from 0.83-0.92, the reflectivity being dependent primarily on the UV, visible, and IR wavelengths. Assuming
a conservative average solar reflectivity of 0.86, this would indicate that 86% of the solar radiation is being reflected back into
the atmosphere and that only 14% of the remaining solar radiation would be absorbed (cf. "absorptivity") and converted to
heat energy.
Thermal emissivity is the ratio of the radiation intensity of a non-blackbody to the radiation intensity of a blackbody at the
same temperature. This ratio, which is usually designated by the Greek letter e, is always less than or just equal to one. The
emissivity characterizes the radiation or absorption quality of non-blackbodies. Emissivity is a physical property... just like
weight, color, shape, etc. All materials have emissivity ranging from zero to one.

Roof/Wall Heat Transfer Model

The steady state conservation of energy equation (energy balance) is used to examine
the outside surface of a roof or wall, where the "system" is considered the roof or wall surface.
The surface is hot already (steady state condition) due to the solar energy absorbed by the
surface. Also, because the surface is hot, it is losing energy to the air (by convection and by net
thermal radiation) and through the roof or wall to the inside of the building (by conduction).

Wall/Roof Heat Transfer Model

An "energy balance" (steady state conservation of energy) equation is written
for the outside surface of the wall or roof:

Energy entering surface = Energy leaving surface
Solar energy absorbed by surface = Heat lost to outside air from surface (net
thermal radiation + convection) + Heat conducted through wall from surface to
inside

The flow of heat to, from, or through a roof, a wall, or a petrochemical tank will occur via one
or more of the three modes of heat transfer:

Mode Factors
Radiation Solar Reflectivity Thermal Emissivity
Conduction Resistivity (R-value) Conductivity (K-value)
Convection Temperature Velocity

Conduction is defined as heat flow through matter resulting from the physical contact or the
transmission of heat by molecular motion. Conduction is also explained as the "transfer of
energy caused by physical interaction among molecular, atomic, and subatomic particles of a
substance at different temperatures." Heat Transfer, Lindon C. Thomas - Professional Version,
p.5.

Hence, the effectiveness of insulation intended to reduce conduction heat transfer is inversely
proportional to the conductivity (K-value) of the material and is directly proportional to the
thickness of the material. Together, these two parameters determine the thermal resistance
(R-value) of the material. For the rate of heat flow through a roof or wall, the conduction heat
transfer (qconduct) is directly proportional to the surface area (Ax) of the roof, the material's
conductivity (K), and the temperature difference (T1-T2) through the roof, and is inversely
proportional to the roof's thickness (L). A heat flux is defined as the rate of heat transfer per
unit area (q"=q/ A).

One-dimensional molecular conduction heat transfer

qx = -kAx (∂T / ∂x)

qx = kAx ( [T1 – T2] / L)

q”conduct = k ( [T1 – T2] / L)

One-dimensional conduction heat transfer in a plate
with T1 > T2,qy = 0 and qz = 0.

Convection occurs with the transfer of thermal energy by actual physical movement from one
location to another of a substance in which thermal energy is stored. Convection heat transfer
is the "special" case of conduction heat transfer at the surface between a solid and a fluid. The
fluid flowing next to the solid surface develops a slow moving boundary layer (film layer), and
heat is conducted through this film to or from the solid surface. The heat flux for convection
heat transfer depends directly on the film coefficient (hfilm/ similar to conductivity) and directly
on the bulk fluid solid surface temperature difference (Tsolid – Tfluid).

Convection Heat Transfer
Convection Heat Transfer is the "special" case of conduction heat transfer at the surface
between a solid and a fluid.

• The fluid develops a slow-moving boundary layer (the film) next to the solid surface.

• Heat is "conducted" through this film - the process is called Convection Heat Transfer.

Convection Heat Flux
• Heat flux for convection through a film (Newton's Law of
Cooling):
q convect = h film (T solid – T fluid)
Where
hfilm = Film coefficient
= Value depends on fluid properties and how fast fluid is moving (faster velocity gives
bigger h, more convection heat transfer)
Tfluid = Bulk fluid temperature
Tsolid = Wall temperature at fluid interface

Radiation heat transfer refers to the electromagnetic energy radiated by solids, liquids, and
gases. Such radiant energy is in the form of electromagnetic waves covering the entire
electromagnetic spectrum from the radio-wave portion of the spectrum through the infrared,
visible, ultraviolet, x-ray, and gamma-ray portions.

For practical purposes, we can consider two types of radiation: solar radiation (energy
emanating from the sun) and thermal radiation (energy emanating from objects on earth).
However, all radiation heat transfer is proportional to the fourth power of a material's surface's
absolute temperature and directly related to the surface's emissivity (fraction of a perfect
"black" emitter).

Radiation Heat Transfer
Radiation heat transfer is the electromagnetic radiation emitted by a surface due to its temperature
(excitation of electron levels).
• Radiation heat flux equation:
q”rad = ε SURFACE σ T4 SURFACE

Where

Tsurface = Absolute temperature (˚Kelvin = 273 + C˚)
σ = Stefan-Boltzman Constant (5.670 x 10-8 W/m2 K4)
εSURFACE = Emissivity, a property of the surface indicating what fraction of a perfect (black)
emitter the surface is.

Solar radiation reaching the earth (i.e., the roof or walls of a building, or the surface of a tank)
has a high energy content (Ultraviolet, Visible, and Near Infrared rays). It is transmitted on
short wavelengths with high frequency. The higher the energy content, the higher the building
surface temperature. The solar radiation flux normal to a surface is called "irradiation," G, and
its value depends on time of year, time of day, location on earth, and local weather.

An opaque roof or wall will either absorb or reflect the solar radiation hitting it. The solar
absorptivity, αso|ar’ is the fraction of solar flux absorbed, while the solar reflectivity, pso]ar’ is the
remaining fraction of the solar flux, which was reflected. Thus,
αsolar + psolar =1

Radiation: Solar and Thermal
• Solar
o Emanating from the sun
o High energy content (U/V, Visible, NIR)
o Short wavelength, High frequency
• Thermal
o Emanating from every object on earth
o Low energy content (MIR, FIR, XIR)
o Long wavelength, Low frequency

Thermal radiation has lower energy content (Middle Infrared, Far Infrared, and Extreme
Infrared rays). This lower level energy travels on long wavelengths with low frequency.
Everything on earth above absolute zero (-459%F or -273%C) radiates energy in the form of
thermal radiation. Thus, not only is every surface emitting thermal radiation, but the surface is
also being hit by thermal radiation emitted from those materials surrounding it. The surface's
net thermal radiation flux, the emitted radiation minus the absorbed radiation from the
surroundings, must be taken into account.

Net Thermal Radiation Heat Transfer, q"NET THERMAL

Since all "earthly" objects emit thermal radiation at each other, the "net" thermal
radiation for a given surface is what is needed:

q"net thermal + q”emitted surface – q” absorbed surroundings { q” air + q” bldgs + q” ground + …}

Therefore:

q"net thermal = ε surface σT4 surface – α surface σT4 surroundings

and

ε surface thermal ≈ α surface thermal

T surroundings ≈ Tair

Therefore:

q"net thermal = ε surface σ (T4 surface – T4 air)

Since the thermal properties of absorptivity, reflectivity, and emissivity of a surface depend on
wavelength (i.e., the temperature), the solar radiation and thermal radiation properties should
not be expected to be the same (they aren't!). However, for thermal radiation surfaces, it can be
shown that thermal emissivity and thermal absorptivity are related by:

ε surface thermal ≈ α surface thermal

SURFACE TEMPERATURES AND BUILDING LOAD EQUATIONS

The development of the equations for calculating outside and inside surface temperatures and
heat gains through roofs, walls, and tanks is presented below.

Outside Surface Thermal Calculations

Looking at the equations below for calculating heat flux due to conduction3, convection4, and
net thermal radiation5, each equation has the surface temperature as an unknown value. If the
surface temperature can be determined, then the heat fluxes can also be calculated. By using
the energy balance equation and substituting in the individual heat flux relations, it is shown
below that the surface temperature of the wall or roof can be found.

An energy balance equation is written for the outside surface of the wall or roof:



An "energy balance" equation is written for the inside surface of the wall or
roof:


q”CONDUCT = q”NET THERMAL RADIATION + q” CONVECT

Then the individual equations are substituted for each of the heat fluxes:

Absorption Net Thermal Radiation Convection Conduction

(l-p)G = εtherm σ (T4surf - T4air) + hfilm (Tsurf - Tair) + (K/L)(Tsurf - Tinside)

(l-p)G = εtherm σ T4surf - εtherm σ T4air + hfilm Tsurf - hfilm Tair + (K/L)Tsurf - (K/L)Tinside

(K/L)(Tsurf)+hfilm Tsurf +(εtherm σ) T4surf = (l-p)G +εtherm σ T4air +hfilmTair +(K/L)(Tinside)

Tsurf (hfilm + (K/L)) + (εtherm σ) T4surf = (l-p)G +εtherm σ T4air +hfilmTair +(K/L)(Tinside)

Tsurf + (εtherm σ /hfilm + (K/L) T4surf = ((l-p)G +εtherm σ T4air +hfilmTair +(K/L)(Tinside))/hfilm + (K/L)

For a given set of environmental conditions (G, Tajr , T insjde , hfilm) and given roof or wall
properties (K, L, psolar, ethermal), rearranging the above equation allows us to solve for the
surface temperature:

Tsurf + [(εtherm σ) /(hfilm + (K/L))] T = [(l-p)G + hfilm Tair+ (K/L)Tinside air + εtherm σ T outsideair] / (hfilm + (K/L))
4 4
surf

(εtherm σ) /(hfilm + (K/L)) = C1
4
Tsurf + C1 T surf = C2

C1 and C2 are constants determined by the environmental condition values and material
property values, but Tsurface can be solved iteratively (by estimating — which is quick with a
computer!). Note that with the surface temperature determined, the heat flux through the wall
or roof is easily calculated using the conduction heat flux equation.

Inside Surface Thermal Calculations
The above equation calculates the outside surface temperature when the inside surface
temperature is known. However, generally, the inside air temperature is known (or can be
assumed) and the inside wall or roof temperature is an unknown. The inside surface
temperature can be determined in conjunction (solved for simultaneously) with the outside
surface temperature by writing another equation for the energy balance at the inside surface of
the wall or roof:


An "energy balance" equation is written for the inside surface of the wall or
roof:


q”CONDUCT = q”NET THERMAL RADIATION + q” CONVECT

Then, substituting the individual heat flux equations with the inside conditions (h film inside, T air
inside)
and inside wall or roof emissivity (ε thermal inside) gives the equation:

(K/L)(Tsurfout - Tsurf jn) = εinα(Tsurfin - Tairin) + hfilmin(Tsurfin - Tairin)

Thus, two independent equations have been developed with two independent unknowns (T
surface outside, T surface inside). The equations are able to be solved iteratively together (again estimating
with the computer), and the inside wall or roof ceiling temperature is calculated. Note that
more information is needed now: inside surface thermal emissivity, inside film coefficient, and
inside room air temperature. Also, the heat flux radiated into the room and the heat flux
convected to the inside air may be calculated separately, which may be important in thermal
comfort determinations.

Roof or Wall Thermal Resistance
In the heat flux conduction equation above, the "K/L" term represents the thermal conductance
for a solid wall or roof. For a composite multi-layer wall or roof, this "K/L" is replaced by the
"overall conductance" U, which is the inverse of the sum of the thermal resistances of each
sublayer. So the "K/L" term in all the equations above can be replaced by (for the generalized
case) becomes:

K/L → U = 1/ΣR

Using this R-approach, any type of wall or roof can be analyzed by determining its ΣRthermal
value. It is only necessary to know the individual R's for the solids and air spaces, and/or the
attic conditions.

Approximate Building Loads
As mentioned earlier, poorly protected single story industrial buildings may receive 70-90% of
their total heat load through their roof. By using the above equations to determine the roof heat
flux for such a building, q"roof non-ASTEC , we can assume the roof is 80% of the total load and
thus estimate the total building load as:

q"building non-ASTEC = q"roof non-ASTEC / 0.80

To compare the effect on building load when ASTEC coating is used, the roof heat flux with
ASTEC, q"roof ASTEC , would be determined from the equations. To this ASTEC roof heat flux
would be added 25% of the non-ASTEC roof heat flux, which represents the estimated load
from the walls (untreated) of the building. This is calculated as:

q"building ASTEC = q"roof ASTEC + 0.25 q"roof non-ASTEC

Thus, the building's cooling load reduction due to using the ASTEC coating is the difference in
the two building heat fluxes multiplied by the roof area:

Cooling Load Reduction = (q”building non-ASTEC – q” building ASTEC ) x Roof Area

Roof Thermal Expansion
For metal roofs, the expansion and contraction of the metal is often a maintenance and repair
concern due to possible fastener and seam damage. The fractional change in length of a
material due to a one-degree change in temperature is given by the coefficient of expansion, β.
To calculate the extension (or contraction) of a material due to a temperature change, the
change in length is given by:

Length Change = β x Length x Temperature Change

It should be noted that if the temperature change is sudden, as can happen with a
sun-and-clouds situation, the material can be quickly expanding and contracting - and the

higher the roof temperature, the greater this change in length. This effect is known as "thermal
shock."

Using the above mathematical formulations for all three modes of heat transfer we can
calculate the heat transfer through a surface with and without ASTEC.

q" SOLAR ABSORBED = q" NET THERMAL RADIATION + q" CONVECTION + q" CONDUCTION
We can solve heat flux problems for a given environmental condition (G, Tair , and Tinside) and
given surface properties (psolar , εthermal) and determine the roof surface temperature, the inside
temperature, the heat flux reduction, the cooling load reduction, and the energy savings in
Kilowatt-hours.
Input Values Needed
For the calculation of outside and inside surface temperatures and the heat flux
through the roof or wall, site specific values are needed for the elements in the three
following groups:

Roof/Wall Thermal Properties Reference
1) Outside surface solar reflectivity Table 1
2) Outside surface thermal emissivity Table 1
3) Inside surface thermal emissivity Table 1
4) Total surface-to-surface thermal resistance Table 1

Environmental Conditions Reference
1) Outside air temperature Specified by User
2) Inside air temperature Specified by User
3) Solar radiation flux Tables 4 / 5

Other Values Reference
1) Outside air film coefficient Given
2) Inside air film coefficient Given

Values for these input variables are presented in tables found at the end of this guide.
Examples:

The following two examples illustrate ASTECs energy analysis of:

1. A metal roof without insulation or air conditioning but with ASTEC protection.

2. A metal roof with insulation, air conditioning, and ASTEC protection.

Calculations can be produced for similar energy savings for any kind of surface
(concrete, galvanized metal, asbestos tiles, etc.) with and without ASTEC.

Calculating Roof Top and Bottom Temperatures
With Roof Heat Flux
(metric units input)

Case 1: Metal Roof without insulation but with ASTEC protection and A/C

Input Roof Thermal Properties

top reflectivity = 0.8
top emissivity = 0.9
bottom emissivity = 0.25
total resistance = 0.002 (m °K)/W 0.011357 (hr ft °F)/Btu

Input Environmental Conditions
outside air temp = 35 °C 95 °F
inside air temp = 20 °C Aircon1 68 °F
solar radiation = 750 W/m2 237.96 Btu/(hr - ft2)

Other Values Used
stefan-boltzmann =5.67E-08 W/(m2 °K4) 1. 71E-09 Btu/(hr ft2 ° K4)
outside air film coeff =5.7 W/(m2 °C) 1.003786 Btu/(hr ft2 °F)
inside air film coeff =5.7 W/(m2 °C) 1.003786 Btu/(hr ft2 °F)

Solution Procedure
Step 1: Guess a roof surface temp => 37.6 °C 99.68 °F
If calculated surface temp is lower, guess bigger surface temp in Step 1

Step 2: Compare calculated surface temp => 37.61306 °C
Roof surface temp = 37.61306 °C 99.70351 °F
Roof bottom temp = 37.36105 °C 99.24989 °F
Roof heat flux = 126.0075 W/m 2 39.97967 Btu/(hr - ft2)

1. Building is air conditioned

With Roof Heat Flux

Case 2: Metal Roof without insulation and without ASTEC but with A/C



inside air temp = 20 °C Aircon1 68 °F

Other Values Used

Solution Procedure


Astec, The Total Solution

Case 1 Roof Heat Flux with Astec = 126.0075 W/m2 39.97967 Btu/(hr -
ft2)
Case 2 Roof Heat Flux without Astec = 342.9916 W/m2 108.8244 Btu/(hr -
ft2)
Heat Flux reduction with Astec = 63.26221 %


Cooling Load Reduction with ASTEC
Q building non-astec = Q roof non-astec / 0.8 428.7395

Q building astec = Q roof astec + 0.25 Q roof non-astec 211.7554

AC Reduction = Q building non-astec + Q building astec 216.984

Case 1: Metal without insulation but with ASTEC protection and A/C

AC Reduction = 428.7395 W/m2 - 211.7554W/m2

Cooling Load Reduction = 216.984 W/m2 68.84469 Btu/(hr - ft2)

Sample Area: 1000 m2
Sample Savings: 216984 Watts or 740414.6 Btu/hr or 61.71332 tons of refrigeration


With Roof Heat Flux

Case 3: Metal Roof without insulation or A/C but with ASTEC protection



inside air temp = 40 °C No A/C1 104 °F

Other Values Used

Solution Procedure


1. Building is not air conditioned


With Roof Heat Flux

Case 4: Metal Roof without insulation or A/C and without ASTEC protection



inside air temp = 40 °C No A/C1 104 °F

Other Values Used

Solution Procedure

Roof heat flux = 268.8753 W/m2 85.30875 Btu/(hr - ft2)

Astec, The Total Solution

Case 1 Roof Heat Flux with Astec = 34.5584 W/m2 10.96469 Btu/(hr -
ft2)
Case 2 Roof Heat Flux without Astec = 268.8753 W/m2 85.30875 Btu/(hr -
ft2)
Heat Flux reduction with Astec = 87.14705 %

1. Building is not air conditioned

Inside Temperature Reduction with ASTEC
(Assume 80% heat flux through roof, 20% through walls in non-ASTEC building)

Tinside astec = Toutside + (Tinside non-astec – Toutside) X (Q roof astec + 0.25Q roof non-astec) / (Q roof non-astec/0.8)

Tinside astec = 35 + 1.314118

Tinside astec = 36.31412 °C 97.36541 °F

MARKET DEMAND
Some of the brightest ideas and some of the smartest inventions never made it to the
market simply because they did not meet customers' requirements.

Unfortunately, some great concepts have also been exaggerated by quasi-manufacturers who
sell on the basis of marketing rather than real benefits.

Informed consumers have become more demanding. In order to meet customers' expectations,
this new approach using radiation control technology had to provide a total solution to roof
management as well as heat management. Above all, to meet customers' expectations, radiation
control technology has to do more than claim heat management efficiency, it has to be proven case
by case with a clear measurement of heat flux reduction and a specific statement of cooling load
reduction based on scientific evidence.

Educated consumers have been able to distinguish between unsubstantiated marketing claims
and scientifically proven systems. Furthermore, it is now well accepted that an experienced
manufacturer has to demonstrate the effectiveness of his system not only in laboratory conditions
but in actual field applications with world-class end users.

The marketplace has since dictated the criteria for a successful solar radiation control system:

1. Energy saving radiant heat barrier
The radiation control coating should be based on proven technology and it should
maintain a high solar reflectivity with a high thermal emissivity. Energy savings should be
calculated using recognized energy balance equations.

2. Reduced heat transfer
Heat reduction based on scientific energy balance equations must be measured in specific
terms (W/m2orBTU/ft2-hr).

3. Better heat management
A high thermal emissivity is the only cost effective way to re-radiate absorbed solar heat.

4. Reduced cooling load
The ability to calculate the cooling load reduction on a structure will provide the means to
determine the payback period and the real lifecycle cost of a system. Cooling load reduction can be
expressed in financial savings per Kilowatt-hour based on the reduction in power requirements
(W/m2 or BTU/ft2 - hr or in terms of tons of refrigeration).

5. Protection against ultraviolet degradation
Specific ASTM or other internationally recognized testing methods can quantify the
U/V resistance of radiation control coatings (RCC).

6. Long lasting waterproofing
Protection against solar heat penetration is insufficient when considering a total solution.
Proper surface waterproofing is necessary to "make the system complete."

7. Surface structural integrity
Roof surfaces require a monolithic application in order to maintain a uniform
quality of insulation and waterproofing. Finish coats should not chip, crack, or flake.

8. Corrosion control
In the case of galvanized metal a proven rust inhibitor is essential to protect the metal from
corrosion due to high levels of relative humidity water penetration, leaks, etc. The metal priming
coat should neither penetrate nor discolor the finish coat.

9. Environmentally friendly products
The preservation of the environment is no longer a debatable issue. Radiation control coatings
should be water-based.

10. Low lifecycle cost factors

a) Longevity. It is not sufficient to have a short payback period. Lower lifecycle cost requires a.
system to guarantee a longer surface life for several years.

b) Low installation cost Initial installation cost should also be supported by a labor warranty
offered by a factory-trained applicator.

c) Low surface maintenance and repairs. This is particularly true of roof surfaces. Adequate
surface preparation (corrosion control and waterproofing) plus an effective finish coat with
exceptional thermal properties will create the condition for a more stable roof surface temperature.
Lower and more stable roof surface temperature will prevent thermal shock and minimize
maintenance and repair costs.

d) Reduced capital expenditures. Cooler surface temperatures mean less heat transfer and more
energy savings. Less heat transfer also minimizes the need for additional capital investments (i.e.,
air conditioning equipment).

How Does ASTEC Meet Customers' Needs?

Criteria ASTEC

Energy Savings Provides high solar reflectivity: more than 0.86
Limits radiant heat absorption to below 14%
Reduces surface temperatures by as much as 20" C
Reduces energy consumption by 40% to 65% ASTEC's
Harmonized Classification Code: 6R06.90.000

Reduced Heat Transfers Measured and calculated heat transfer reductions: 50% to
70%
Better Heat Management Thermal Emissivity: 0.92

U/V Protection Uses high density ceramic component to resist ultraviolet
penetration and to maintain its color. ASTM C-25
Accelerated Weathering

Long-lasting Waterproofing WPM #8: Tensile Strength: 167 PSI
Elongation: 245% break
WPM #9: Tensile Strength: 792 PSI
Elongation: 683% break

Structural Integrity Every component of the ASTEC system is highly flexible
and provides a strong adhesion for a monolithic
application.
Corrosion Control ASTEC's metal primer seal (B-16-71) inhibits corrosion and
prevents oxidation from air and humidity. Salt-spray/
Salt-fog resistance ASTM B-117-90.

Protection of the Environment ASTEC products are waterbased and offer a clean and
aesthetic architectural appearance.

Lifecycle Cost Minimal labor cost due to ease of application; 7- to 10-year
product amortization cost due to warranty; reduced
maintenance and repair costs due to stable surface
temperatures; and energy savings due to cooling load
reductions.

Sound Attenuation ASTEC is proven to dampen vibration and to deaden
sound.

Cost-effective Installation Application by brush, roller, or power spray equipment.

Warranty Manufacturer's Product warranty. Labor warranty by
factory-trained ASTEC applicators.

Low-cost Maintenance Easy do-it-yourself repair. Annual inspection during
warranty period.

Lower Roof Repair Cost Virtual elimination of thermal shock on metal surfaces.

Brand Name Recognition ASTEC is #1: It was the first ceramic-based liquid-applied
RCC , and it remains the world leader with a strong
technical support team dedicated to its exclusive
factory-trained dealers in every continent of the world. A
20-year proven record.
Prestigious client reference list:
Industrial sector
Commercial sector
Petrochemical sector
Residential sector
Military sector

Fire-safe Products Self-extinguishing, Class A fire rating. ASTM D-1360.

Mildew/Fungus Resistance ASTM D-3273-73T

ASTEC is the Total Solution

TABLES
Table 1 Building Material Properties
Table 2 Roof's Airspace Resistances
Table 3 Attic's Airspace Resistances
Table 4 Clear Day Solar Radiation Values
Table 5 Cities and Solar Radiation

Table 1
Building Material Properties
Ref: Chapter 22,1989 ASHRAE Fundamentals Handbook

Material Type and Description Material Density Thermal Resistance Solar Thermal
R-Value Reflectance Emittance
(Kg/m3) (Ibm/ft3) K m2/W (h ft2°F)/BTU
Roofing

Aluminum sheet 0.55 0.1
Galvanized iron, oxidized 0.2 0.25
Asbestos cement shingles 1900 118.61 0.037 0.210112 0.27 0.89
Asphalt roll roofing 1100 68.67 0.026 0.147646 0.07 0.9
Asphalt shingles 1100 68.67 0.077 0.437259 0.07 0.9
Wood shingles 0.166 0.942663 0.41 0.9

Masonry

Brick, fired clay 2000 124.86 1.00* 5.679* 0.93
Clay tile, one cell (102 mm / 4.02 in.) 0.2 1.136 0.35 0.85
Concrete, stone aggregate 2200 137.34 0.60* 3.407* 0.35 0.87
Concrete, low density aggregate 1200 74.91 2.00* 11.357* 0.35 0.87
Concrete, foam/cellular 1000 62.43 3.00* 17.036* 0.35 0.87
Cement plaster, sand 1860 116.12 1.39* 7.893* 0.35 0.88
Gypsum plaster low-density (127 mm / 5.0 in.) 720 44.95 0.32 1.817 0.8 0.9
Gypsum plaster, sand (127 mm/5.0 in.) 1680 104.88 0.09 0.511 0.8 0.9

Note: Asterisk (*) indicates R-value per meter (ft) of thickness and needs to be reduced for actual thickness used

Building Material Properties

Material Type and Description Material Density Thermal Resistance Solar Thermal
R-Value Reflectance Emittance
(Kg/m3) (Ibm/ft3) K m2/W (h ft2°F)/BTU

Building Board

Asbestos-cement 1900 118.61 1.73* 9.823*
Gypsum/plaster (12.7 mm / 0.5 in.) 800 49.94 0.079 0.449 0.91
Plywood (12.7 mm/0.5 in.) 540 33.71 0.11 0.625 0.33 0.9
Vapor/permeable felt 0.011 0.062
Hardwoods 700 43.7 6.0* 34.071* 0.41 0.9
Softwoods 500 31.21 7.5* 42.59* 0.41 0.9

Insulating Materials

Mineral fiber batt (90 mm / 3.54 in.) 25 1.56 2.63 14.935 0.93
Glass fiber 100 6.24 27.7* 157.3*
Expanded polystyrene 2 0.125 4.35* 24.702*
Mineral fiberboard
- Core/roof insulation 260 16.23 20.4* 115.84*
- Acoustical tile 290 18.1 19.8* 112.44*
Loose-fill pertite, expanded 90 5.62 21.0* 119.25*
Spray polyurethane foam 32 1.998 41.0* 232.82*

Note: Asterisk (*) indicates R-value per meter (ft) of thickness and needs to be reduced for actual thickness used

Table 2
ROOF'S AIRSPACE RESISTANCES

Parameters: t = airspace thickness; EI, E2 = emissivity values of surfaces facing airspace

There are two cases for which the airspace resistance will be found:

Case 1: Normal materials give an effective emissivity of 0.82 (Ei = E2 = 0.9)
Case 2: One surface has low emissivity (Ei = 0.25, i.e. galvanized iron) and the other surface has regular emissivity (E2 = 0.9). This
situation provides an effective emissivity of 0.20

ROOF AIRSPACE R-VALUE
Thickness of Airspace

cm in. cm in. cm in. cm in.
1.27 0.5" 1.91 0.75" 3.81 1.5" 8.89 or 3.5" or>
>
2 2 2 2 2 2 2 2
(m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu
Horizontal
Airspace
Case 1:E = 0.82 0.136 0.77 0.15 0.85 0.166 0.94 0.176 1
Case 2: E = 0.20 0.294 1.67 0.37 2.1 0.491 2.79 0.601 3.41
45° Sloped
Airspace
Case 1:E = 0.82 0.136 0.77 0.148 0.84 0.16 0.91 0.159 0.9
Case 2: E = 0.20 0.294 1.67 0.37 2.1 0.451 2.56 0.439 2.49

Table 3
ATTIC'S AIRSPACE RESISTANCES

Rtotal = Rroof + Rattic air + Rceiling

Parameters: Attic ventiliation, outside air temperature (OAT), ceiling R-value, roof surface temperature.

AIR ATTIC R-VALUE
OAT Roof
Temp No Ventilation Case Natural Ventilation Case Forced Ventilation Case
Ceiling R Values Ceiling R Values
2 2 2 2 2 2 2 2 2 2
(m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu (m K)/W °Fft hr/Btu
1.76 10 3.52 20 1.76 10 3.52 20
32 °C/90 °F
49°C/120°F 0.1057 0.6 0.211 1.2 0.264 1.5 0.845 4.8 1.532 8.7
60°C/140°F 0.1057 0.6 0.229 1.3 0.317 1.8 1.109 6.3 1.884 10.7
71°C/160°F 0.1057 0.6 0.247 1.4 0.37 2.1 1.268 7.2 2.236 12.7
38°C/100°F
49°C/120°F 0.1057 0.6 0.158 0.9 0.176 1 0.475 2.7 0.828 4.7
60°C/140°F 0.1057 0.6 0.194 1.1 0.247 1.4 0.792 4.5 1.303 7.4
71°C/160°F 0.1057 0.6 0.229 1.3 0.335 1.9 1.039 5.9 1.708 9.7
NOTE: If two reflective surfaces are used on the inside attic surfaces, ADD the next values; if only one reflective surface is used, then ADD only
half of the following values: 0.81 4.6 0.898 5.1 0.989 5.1 1.057 6 1.057 6

Table 4
Clear Day Solar Radiation Values For a Horizontal Surface

The ASHRAE "Clear Sky/Day" method of calculating solar radiation (insolation) values is based
on a standard (low moisture) atmosphere model. The parameters used to determine the radiation
values on an hourly basis are:

1 Time of year (earth's declination angle)
2 Time of day (hour angle)
3 Location on earth (latitude angle)

The radiation values calculated below have set two of the above parameters at the following
values:

(a) Mid-summer is chosen: June/July for the Northern Hemisphere
January/Feb. for the Southern Hemisphere
This means the declination angle is set at 22°

(b) Solar noon-time is chosen: the highest point in the sky each day at the location.

This means the hour angle is (0°) zero degrees

Thus, the calculation of "Clear Day" summer noon-time radiation is reduced to only one
parameter: The latitude angle for that location

Summer Noon-Time Radiation on a Horizontal Surface

Latitude Zenith Clear Sky Hourly Conservative Hourly
(degrees) Angle (1) Radiation Radiation(2)
W/m2 Btu/(h ft2) W/m2 Btu/(h ft2)

0° 22° 950 301 855 271
10° 12° 1000 317 900 285
20° 2° 1018 323 915 290
30° 8° 1012 321 910 288
40° 18° 980 311 880 279
50° 28° 900 285 810 257
60° 38° 775 246 700 222
(1)
Notes: Zenith angle is the angle between the incoming solar radiation and
a vertical line.(2) The “conservative Value is 90% of the clear sky
value to account for moisture, pollution, etc.

Using Table 4 with a city’s latitude gives the solar radiation value for that city.

Table 5

CITIES and SOLAR RADIATION
Clear day, summer, noon-time

City Country Latitude Solar Radiation
W/m2 Btu/(hr ft2)
AFRICA
Cairo Egypt 30° 910 288
Johannesburg S. Africa 26° 912 289
Lagos Nigeria 6° 880 279

ASIA
Bangkok Thailand 13° 905 287
Bombay India 18° 912 289
Colombo Sri Lanka 7° 887 281
Hong Kong China 22° 914 290
Jakarta Indonesia 6° 882 280
Kuala Lumpur Malaysia 3° 865 274
Manila Philippines 14° 907 288
New Delhi India 13° 905 287
Singapore Singapore 1° 860 273

MIDDLE EAST
Dhahran Saudi Arabia 26° 906 287
Muscat Oman 23° 913 289
Kuwait City Kuwait 29° 909 288

EUROPE
Budapest Hungary 48° 825 261
Izmir Turkey 38° 885 281
Lisbon Portugal 38° 885 281
Prague Czech Republic 50° 810 257

CARIBBEAN
Nassau Bahamas 25° 918 291
Montego Bay Jamaica 18° 912 289
Sto Domingo Dominican Republic 18° 912 289
San Juan Puerto Rico 18° 912 289
Port of Spain Trinidad & Tobago 10° 900 285

NORTH AMERICA
Acapulco Mexico 17° 911 289
Merida Mexico 21° 916 290
Mexico, D.F. Mexico 20° 915 290
Ottawa Canada 45° 850 269

SOUTH AMERICA
Bogota Colombia 5° 877 278
Buenos Aires Argentina 35° 895 284
Caracas Venezuela 10° 900 285
Guyaquil Ecuador 3° 870 276
Lima Peru 12° 903 286
Manaus Brazil 3° 870 276
Montevideo Uruguay 35° 895 284
Recife Brazil 9° 891 282
Salvador Brazil 13° 905 287
Santa Cruz Bolivia 17° 911 289
Santiago Chile 35° 895 284
Sao Paulo Brazil 23° 913 289

CENTRAL AMERICA
Belmopan Belize 17° 911 289
Guatemala, DF Guatemala 15° 908 288
San Pedro Sula Honduras 16° 909 288
Tegucigalpa Honduras 14° 907 288
San Salvador El Salvador 13° 905 287
Managua Nicaragua 12° 903 286
San Jose Costa Rica 10° 900 285
Panama City Panama 9° 891 282

USA (Detailed Listing)
Albuquerque NM 35° 895 284
Atlanta GE 34° 898 285
Baltimore MD 39° 883 280
Bismarck ND 47° 831 831
Boise ID 44° 852 270
Boston MA 42° 866 275
Burlington VT 44° 852 270
Charleston SC 33° 901 286
Charleston WV 38° 886 281
Cheyeen WY 41° 873 277
Chicago IL 42° 866 275
Cincinnati OH 39° 883 280
Concord NH 43° 859 272
Dallas TX 33° 901 286
Denver CO 40° 880 279
Des Moines IA 42° 866 275
Detroit Ml 42° 866 275
Fairbanks AK 33° 901 286
Hartford CT 42° 866 281
Honolulu HI 21° 914 290
Indianapolis IN 40° 880 279
Jakson MS 39° 883 280
LasVegas NV 36° 892 283
Little Rock AR 35° 895 284
Los Angeles CA 34° 898 285

Louisville KY 38° 886 281
Memphis TN 35° 895 284
Milwaukee Wl 43° 859 272
Minneapolis MN 45° 845 268
Montgomery AL 32° 904 287
Newark NJ 41° 873 277
New Orleans LA 30° 910 288
New York NY 41° 873 277
Oklahoma City OK 35° 895 284
Omaha NE 41° 873 277
Ortando FL 29° 911 289
Philadelphia PA 40° 880 279
Phoenix AZ 33° 901 286
Pierre SD 44° 852 270
Portland ME 44° 852 270
Portland OR 46° 838 266
Providence Rl 42° 866 275
Raleigh NC 36° 892 283
Richmond VA 38° 886 281
Salt Lake UT 41° 873 277
Seattle WA 48° 824 261
St. Louis MO 39° 883 280
Washington DC 39° 883 280
Wichita KS 38° 886 281
Wilmington DE 40° 880 279

Astec Engineer Guide

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Astec Engineer Guide

Semelhante a Astec Engineer Guide (20)

Mais de Tony Loup

Mais de Tony Loup (20)

Último

Último (20)

Astec Engineer Guide