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ROOF COOLING TECHNOLOGIES /
HISTORY / PHYSICS
PRIMARY ROOF COOLING TECHNOLOGIES
Click
"E-Cool" to view or
download slide presentation of - Why the Roof /Roof Cooling Technologies in
Adobe Reader.
Roof Cooling Technologies fall into two categories: Re-Active and
Pro-Active. For purposes relating to the roof, there are two
distinct technologies for each category.
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RE-ACTIVE:
As the name implies, it reacts by
reflecting rather than dispersing or dissipating heat away from the building
component (roof) to which it is installed over or applied to. This
resistive effort usually comes at a price, in the form of decreasing efficiency
as the product ages. It not usually associated with Green Technologies, and is
primarily associated with prefabricated or manufactured products currently
utilized in standard roofing system or maintenance applications. Re-Active
estimated savings are more subjective, requiring long term monitoring, than Pro-Active systems, that
can actually measure anticipated reduction in energy dollars.
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PRO-ACTIVE: As
the name implies, it serves to utilize a combination of Green and either
Aerospace or Mechanical Technologies to dissipate/disperse rather than reflect heat
from the roof surface.
By using renewable energy sources, the ancillary benefits to the environment
can be taken into account. A Pro-Active system can more readily measure
anticipated savings, by taking building construction, occupancy and utility
rates and applying mechanical calculations. Pro-Active systems do not lose
efficiency over their life cycle.
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RE-ACTIVE -White Reflective Roof
Coatings
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Maintenance Oriented
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Formulation / Applicator Sensitive
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Coating versus Waterproofing
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Decreasing Efficiency
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Must be replaced with roof
replacement
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Subjective Savings Evaluations.
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RE-ACTIVE- Single Ply Roof
Membranes
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White PVC & TPO Systems
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Subjective Savings Evaluations
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Subject to Environmental
Degradation / Aging.
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PRO-ACTIVE - Mechanical Equipment
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Recycled Water / Evaporative
Cooling / Chiller Units
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Optimal Measured Reduction in
Cooling Costs
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Primary Usage / New or
Retrofit Equipment
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Limited Applications
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Good Payback / Return on Investment
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PRO-ACTIVE - Roof Cooling Equipment
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Ecoology PAIR System
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Optimal Measured Reduction in
Cooling Costs.
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Uses 100% Renewable Resources
(Potable, Recycled, Reclaimed Water)
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Patented Fail Safe Components
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Optimal Payback Period
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Optimal Return on Investment
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Extended Roof Life
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Extended Mechanical Life
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HISTORY OF EVAPORATIVE ROOF COOLING
TECHNOLOGY
Click "E-Cool" to view
complete History of Evaporative Roof Cooling and references.
A Ninety-Year Record Of Innovation,
Experiment And Scientific Fact
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The patent granted to the founder
of eCOOLogy, George Jerome builds on a remarkable record of
effort, experimentation and innovation. Nineteen previous patents are cited in
the Jerome patent. |
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The concept of PAIR,
evaporating water on the roof’s surface to remove solar energy and reduce roof
temperatures, has been tried before, the first patents on the subject dating
back to 1910. |
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On July 12, 1910, William
Crawford received a patent for a system that sprayed water on a roof, cooling
the roof and the interior of the building. He then caught the run-off in the
rain gutters, using the excess water, to water the adjacent lawn. |
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In 1987, S. Somasundaram,
Assistant professor of Mechanical Engineering at Texas A&M University, and his
Graduate Research assistant in the Energy Systems Laboratory, A. D. Carrasco,
conducted an extensive experiment of the effects of water based roof cooling,
using a 25,000 square foot building in Texas. |
-The results were published in a
report, AN EXPERIMENTAL AND NUMERICAL MODELING OF A ROOF-SPRAY COOLING SYSTEM.
While this is one of about 50 such experiments and subsequent reports, its
results are typical of all of the research efforts. As these gentlemen put it:
“This paper describes the design
and installation of a roof-spray cooling system on a large well-insulated office
building. . . . . The results showed a substantial reduction in the heat
transfer rates and the surface temperatures of the roof, together with a
reduction in the inside temperatures.”
"The present study was carried out
on a large one-story building in Bryan, Texas, with a flat roof
construction...... The building also has a good insulation blanket below the
roof (R-19) and is completely air-conditioned. ....... The experiment was
designed to quantify the amount of heat transferred through the roof under both
sprayed and unsprayed conditions. “
References And Other Scientific
Experiments And Reports On Roof Cooling:
The History Of Water-Based Roof
Cooling
Starting with William Crawford’s
early attempts to keep solar energy from super-heating a roof, there has been a
long progression of improvements and innovations.
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In 1940, F. C. Houghton, director
of ASHVE, the forerunner of ASHRAE, and several associates, conducted a study
of roof cooling and issued a report entitled "Summer cooling load as
affected by heat gain through dry, sprinkled and water covered roofs."
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In 1941, patent 2,266,321 was
issued to Leonard Holder for a device that addresses the “prevention of
excessive heat accumulation in exposed surfaces such as roofs.” Importantly,
Holder recognizes that evaporative cooling efficiently removes energy, while
the excessive application of fluid on the surface decreases the effect. |
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Patent 2,506,936, to Alfred
Murray in 1950 continues the refinement of the cooling process by first
reiterating the correct statement; “If only a small amount of water is placed
on the roof, the evaporation is highly accelerated as compared to what would
be if the roof surface were flooded with water.” |
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Patent 2,660,863, to Carlton
Gerhart in 1953 utilizes a porous hose to effectively drip-irrigate the roof.
As in other patents, the potential for rot and mildew precludes use of this
concept. |
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Finally, in 1988, Stephen Viner
patented a technological advancement in his patent 4,761,965. He describes a
very specific arrangement of an evaporative roof cooling system, including a
“plurality of water distribution ...nozzles, a “conduit means”, a solenoid
valve, and a “temperature measurement means comprising a thermistor”. Viner,
like his predecessors, espouses the need to apply water in a thin film, allow
it to evaporate, and then repeat the application. Also like his predecessors,
Viner falls into the trap of presuming that a timed cycle of water on/ water
off will achieve the goal of optimum application of water. This timed sequence
will never account for the variations in temperatures, variations of the water
absorption of the roof. |
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It would be 13 years after the
Viner patent that the eCOOLogy patent, encompassing nine decades of research
and innovation, coupled with the aero-space background of its founder, would
bring together unique technologies and answers to problems that eluded all of
these pioneers. |
PHYSICS 101-
EVAPORATIVE ROOF COOLING
Click "E-Cool" to view
complete Physics 101.
Part I - It has to work, It's the law
of physics.
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Gravity requires rain to fall to
the ground, fire heats and water cools. This statement is not based upon data
compilation for accelerated weathering testing, monitoring installation
techniques / manufacturing processes or long-term product field performance.
This statement is based upon the law of physics. These same laws of physics
govern the operation of eCOOLogy! |
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One gallon of water will remove a
given number of BTU's of heat. As long as water is H2O, the laws of physics
mandate that ECOOLogy works. |
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The eCOOLogy system is an anomaly
in the world of energy savings and roof cooling systems. It is generally
assumed that the eCOOLogy system falls under the same blanket criteria as
reflective roof coatings. Apples and Oranges, nothing could be further from
the truth: |
eCOOLogy Systems Inc. (ESI)
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ESI manufactures roof
level equipment systems, using patented aerospace technology, to deliver
metered amounts of water to cool the roof surface for the purpose of reducing
energy consumption. |
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ESI equipment is installed
over a roof system, not applied to it. |
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ESI is a delivery system
for water (H2O) to disperse roof heat. |
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One gallon of water
disperses 8,265 BTU's of heat. |
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ESI maintains the roof at
about 99 degrees. The amount of water necessary to achieve this, determines the
amount of energy that must be disbursed. |
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ESI utilizes potable or
reclaimed water and existing water hookups. |
Part II - How Does it Work.
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The roof receives energy from the
Sun - solar energy. This energy comes through the atmosphere, heating it as it
penetrates, finally impacting the roof. Some of this energy heats the roof
surface, and some is reflected back into the atmosphere. The energy reflected
back further heats the air as it move up from the roof. Air movement
convectively carries some heat energy away. |
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You can visually see this
phenomenon. Look at the roof of your car on a hot day. The air directly above
the roof will shimmer with the added heat energy it absorbs from the solar
energy. The "boundary layer" of this heated air will be between an inch and
two inches thick. On a large roof, this layer will generally be considerably
deeper. |
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The energy absorbed by your roof
surface increases its temperature dramatically, heating the roof structure and
insulation below your roof surface. |
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According to our physics
professor, and the laws of physics, one gallon of water requires [absorbs]
8,265 BTUs to evaporate - go from a liquid state to a gaseous state. |
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Water, properly applied to your
roof, will remove most of that solar energy heating your roof. Instead of 165
degrees, your roof will be kept at a much cooler 95 to 100 degrees.
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LAW OF PHYSICS
Some important conversion factors:
1 gallon of water absorbs 8,265
BTUs in evaporation
1 Ton of air conditioning = 12,000
BTUs
1 Ton of air conditioner operating
for one hour, consumes about 1.25 KwH
The Sun delivers 344 BTU/ft2/Hr
to the Earth’s surface
An average roof, on a 90 degree
day, can reach 185 degrees F. |
