SABS TESTS CONDUCTED AND RESULTS OBTAINED
Thermal Insulation Coating.
Test report 7222/ 2090038/v 76
Product was tested for:
Heat absorption of air inside treated and non-treated
containers.
Adhesion of thermal coating.
Test methods:
Adhesion - requirements in accordance with SABS ISO 2409 : 1992
Two containers - one coated one non-coated.
Inside temperatures measured with thermocouple at 1 hour
intervals
Between 11:00 and 15:00.
Test window:
12 April 2002
Results:
Adhesion - 100 % adhesion, no loss.
Inside Temp - Temp in coated container is always lower than uncoated
by
approx. 18%.
As ambient temp. drops air in coated container drops slower than
uncoated container confirming
insulating properties
Saving Energy with Cooling(Thermal insulating) Roof Coatings
Special roof coatings can save energy in hot
climates and can help utilities in warm climates reduce peak demand.
Architects are using special coatings to cool off buildings in hot
climates, but until recently there was little research on the measured
cooling-energy savings of these roofs.
Over the past two years, however, researchers in
Florida and California have examined the impact of these roof coatings
on air-conditioning energy use in retrofits of monitored homes.
Simulation analysis suggests that a specially coated roof can cut
a building's cooling load by 10-60%. The higher numbers are associated
with uninsulated roofs.
Cooling coatings are increasingly being used
for manufactured homes in the Southeast, based on homeowner reports that
such coatings can reduce summer air conditioning costs. Until now,
however, no investigation in a cooling-dominated climate examined the
effect of coated roof on time-of-day air conditioning electrical demand
in occupied residential buildings--important information for utilities
where summertime peak demand is a concern.
One of the earliest whole-building studies that
measured cooling-energy savings from cool roof coatings was performed by
the Mississippi Power Company. The utility monitored two identical
side-by-side single-story commercial office buildings after the roof of
one had been covered with a cooling coating. Both existing buildings had
R-11 roof insulation. The results of the experiment? Summertime air
conditioning was reduced by 22% in the building with the reflective roof
coating.
More recently, researchers at LBL measured very
significant cooling-energy savings from applying cooling coatings to
three buildings in central California . At one site, energy demand
for space cooling was nearly eliminated. But regardless of the potential
of cooling roof coatings in California, Florida's higher humidity and
nighttime temperatures make prospects for near elimination of space
cooling energy use in that state very unlikely.
An Initial Experiment
In the summer of 1991 we conducted a preliminary
experiment in Merritt Island, Florida. Our first test building (Site #0)
was a 1,800 ft2 detached single-family, single-story home of
conventional concrete-block construction. The pitched roof faced
north-south, with plywood decking covered by green/gray asphalt
shingles. The home's attic was well insulated with approximately two
inches of fiberglass covered by an additional six inches of cellulose
insulation, yielding a thermal resistance of about R-25. Air
infiltration from the attic area into the conditioned interior (a common
problem due to duct leakage), had been largely eliminated in a previous
audit and retrofit. Beginning in May 1991, we submetered the home's air
conditioner while maintaining a constant thermostat setting of 79deg.F.
We also recorded the underside roof deck, attic air, and living room
temperatures.
When we applied the cooling coating on September 5
of that year, the roof's reflectivity increased from 0.22 to 0.73.2
Spot measurements under full sun at midsummer had shown shingle surface
temperatures of 160-170deg.F, prior to the roof treatment, compared to
110deg.F after we applied the coating. Analysis assuming an 81deg.F
average summer temperature indicated that a cooling roof coating would
reduce energy consumption by 10% (35 kWh versus 39 kWh per day).
Yet this test house probably understated the
savings, since most existing Florida residences have fairly poor attic
insulation and attic air frequently leaks into the conditioned
interiors. Therefore, we obtained more "typical" residences for the
detailed experiments we conducted the following year.
A Five-House Follow-up
To learn about how cooling roof coatings affect
peak cooling demand we measured the 15-minute air-conditioning
electricity demand in our follow-up study, along with meteorological
conditions for three weeks before and after each home was retrofitted.
We also used infrared thermography to examine how interior heat fluxes
from the roof/ceiling were altered by the retrofit.
With equipment to instrument two buildings, we
sought one residence with typical ceiling insulation levels
(approximately R-11) and a second structure without any insulation at
all. (Many homes built in Florida prior to 1965 have no attic insulation
and were built with flat roofs that make retrofits difficult.) Data from
Site #1 would be used to obtain results from a more-typical existing
residential building, while Site #2 would help us define the maximum
savings potential for cooling roof coatings in Florida. Experiments on
three more houses in the summer of 1993 extended our sample size. Each
house in the second round of experiments had unique characteristics that
broadened our knowledge of how cooling roof coatings reduce
air-conditioning needs. (Table 1)
Results
Site #1
Site #1 was a fairly typical existing Florida
home. The attic was insulated to approximately R-11, but the air
conditioner was old and inefficient. Although pre- and post- application
air temperatures and solar radiation were comparable, air-conditioning
power demand was reduced by an average of 25% (from 40 to 30 kWh per
day) after we applied the roof coating. The average electrical
consumption of the air conditioning system during the utility coincident
peak period (5-6 pm) was 2.4 kWh before the coating and 1.7 kWh
afterward. This 700 W savings represents a 28% reduction in peak power
demand attributable to the coating. Furthermore, average 24-hour attic
air temperatures were reduced by 6deg.F, while peak attic temperatures
between 2 pm and 6 pm fell by an average of 15deg.F.
Site #2
Site #2 was an ideal candidate for a cooling roof
coating. The house had a flat roof and no space was available to
insulate the ceiling assembly. Prior to the coating, the 2.5-ton air
conditioner was unable to control the interior temperature adequately,
running continuously each day from noon until 7 pm when the thermostat
was finally satisfied.
Average air-conditioner electricity consumption
dropped from 36 kWh to 20 kWh per day after the application--a 43%
reduction. Savings would have been higher if the house had possessed a
larger air conditioner, but the results did demonstrate the huge
potential for gaining cooling-energy savings by applying a cooling
roof coatings to the roofs of homes without ceiling insulation.
The temperature reductions to the deck, deck
airspace and ceilings were also striking, as was the change in the air
conditioner's load profile. Before the retrofit, the daily interior
temperature had ranged above the thermostat set point by 4deg.F or more.
The average electrical demand of the air conditioning system during the
utility coincident peak period (5-6 pm) was 2.2 kW before the coating
and 1.4 kW after the application--a 38% reduction.
Site #3
Site #3 was a small house, cooled with a
through-the-wall air conditioner. Since there was no attic duct system
the site was of unique research value. The attic above the dropped
ceiling contained no insulation, and the 1.5-ton air conditioner ran
constantly prior to the coating (from 1-10 pm) unable to satisfy the
thermostat. After the coating, the air conditioner cycled on and off
during the same time period, maintaining improved interior comfort while
reducing the utility coincident peak demand (5-6 pm) by nearly 960 W.
Total daily air conditioning use was 11.9 kWh lower after the coating
was applied--a reduction of 47% under peak-day conditions. After the
retrofit, the average daily air conditioning savings totalled 5.6 kWh,
or 25% during the summer period (Table 1) and peak demand savings
averaged 30% (500 W).
Site #4
We selected Site #4 to see how applying a cooling
roof coating to a gravel roof (common in South Florida) might reduce
energy use, and also because the household complained of high utility
bills. The ceiling was well-insulated for a Miami home (R--11-R-19 blown
fiberglass) and its 3-ton air conditioner was relatively efficient. But
while auditing the home, we found a large duct-system supply leak in an
inaccessible portion of the attic. (We found the leak with an infrared
camera.) The leak was not repaired, but the roof was later coated with a
cooling roof coating. Although the percentage savings of air
conditioning energy (15%) were lowest at Site 4, the absolute savings of
8.0 kWh per day were nevertheless significant.
Site #5
Site #5 had a tile roof, but the cement barrel
tiles were old and stained a dark gray. The house also had relatively
poor ceiling insulation and an inefficient air conditioner. The measured
solar albedo was 20% before coating, but after being coated with a
sprayed-on cooling coating, it was 64%. The absolute savings at this
site were quite large at 11.6 kWh per day with a 988 W reduction in
coincident peak-cooling demand.
Reflecting on cool roofs
Cool roofs can reduce space-cooling energy
consumption and demand in Florida. Data collected so far suggest that
air conditioning savings of 10-40% can be realized, with the larger
reductions associated with poorly insulated roof assemblies or buildings
with excessive attic air infiltration due to air handler return air
leakage. cooling coatings may be particularly suitable in existing
residences where the roof structure makes it difficult to add
insulation.
Average electricity consumption for central air
conditioning in single family homes in Florida is approximately 4,400
kWh/year. Based on a savings level of 10-40%, cool roofs can be expected
to reduce household electricity use by 440 to 1,760 kWh per year--an
annual savings of $35-$140 at current electricity rates (assuming 8cents
per kWh). Obviously, the savings will vary depending upon the severity
of the cooling season.
What About the Payback?
A frequent question concerns payback of cool
roofing. There are several angles on the answer, but generally speaking,
cooling coatings are most appropriate when one is re-roofing. If the
coating is applied to an existing roof that is in otherwise pristine
condition, the cost equation is straightforward. The typical coverage of
a cooling coating is 25 ft2 per gallon,(0,6 sq. meters per
liter) (Sno-Cote®
gives 6 square meters per liter reducing the application cost factor by
a factor of 10!!!! This makes a massive difference to these calulations
and results) based on an application of two coats to a target
thickness of 40 mils.
Cost for the material from vendors varies by 50%
or more but averages about $60 per 5-gallon container when purchased in
quantity. It is important to keep in mind that roof area is generally
considered greater than building floor area, particularly with a steep
roof pitch. For instance, a typical 1,500 ft2 home may have
2,200 ft2 of roof to be covered. The application then
requires 90 gallons of coating material for a materials cost of
approximately $1,100.
The cost of labor for installation depends greatly
on the roof surface, on whether the coating is to be rolled on or
sprayed, and on labor rates. A typical labor cost might be approximately
50cents per ft2 for the required two applications. Thus the
overall application would cost about $1 per ft2, or
approximately $2,200 for a typical home. With annual energy savings in
Florida of $35-$140, the payback times are long--usually lasting longer
than the roof itself. (With the
exception of Sno-Cote®)
A completely different scenario emerges if the
home is soon in need of re-roofing, however. Here the roof coating
(which essentially creates a new weatherproof surface) might be seen as
a way of extending the life of the roof by 5 to 10 years at half of the
cost of re-roofing. The energy savings then become a side benefit.
For new homes, the situation is even more
interesting. Here it is often possible to choose roofing types--such as
metal roofing, tile roofing, or metal or ceramic shingles--that can be
specified in a reflective white at significant additional cost.
Unfortunately, no truly reflective asphalt roofing shingles yet exist
for the residential market, but this situation may change as researchers
work with the roofing industry to develop new products and spread the
word about the energy benefits to help create a market for the
materials. For commercial buildings, a variety of reflective roofing
materials are already available: Hypalon, white EPDM, and PVC single-ply
membranes. Once such products are widely available for the residential
market, the economics may be significantly altered as the cost of
reflective roofing becomes inconsequential. n
Notes
1. Reflectivity or albedo is the hemispherical reflectivity
integrated over a particular wavelength band of the electromagnetic
spectrum. For the purposes of this article, the terms reflectivity and
albedo are used interchangeably and refer to the wavelengths
encompassing the range of solar irradiance from 0.28 to 2.8 microns.
2. Surface solar reflectivity is measured using a
precision spectral pyranometer with the device alternately faced upward
towards the sun and downward towards the roof to determine the ratio of
incident to reflected solar radiation.
Urban Heat Islands
Large cities typically contain darker surfaces and
less vegetation than rural environments; these circumstances increase
solar gain and thereby raise summertime cooling-energy demand. The dark
surfaces and lack of vegetation also warm the summer air, leading to the
creation of the urban "heat island." In fact, the average temperature in
a typical city on a clear afternoon can be 1deg.F-5deg.F hotter than
that of the surrounding rural area. Researchers at LBL Heat Island
Project estimate that the additional air-conditioning use caused by this
urban air temperature increase is responsible for 5%-10% of urban peak
electric demand, at an annual cost of several billion dollars.
The power needed to compensate for these higher
temperatures requires additional generating capacity, which often
contributes to urban air pollution. Moreover, the elevated temperatures
themselves accelerate smog formation. According to researchers with LBL,
the probability of smog increases by 2%-4% per deg.F increase in maximum
daily temperature. But shade trees and light-colored surfaces can
offset, and may even reverse the summer heat island effect.
In one experiment, LBL examined the savings due to
cooling roofing systems installed on three buildings in Sacramento,
California. One was an occupied residence with R-11 ceiling insulation
under a composite shingle roof. The initial roof reflectivity was
measured at 0.18, and this was altered to 0.78 by application of
acooling roof coating. Furthermore, the air-conditioning cooling load in
the building was reduced by 69%, with a 28% reduction in peak electrical
demand, and the seasonal energy savings amounted to a reduction of
approximately 14 kWh per day and a 1 kW in peak power demand.
The second and third buildings were test
bungalows. In both cases, the buildings' corrugated metal roof albedo
was increased to approximately 70%, and measured air conditioning energy
use was reduced by approximately 40%-50%.
Table 1. Results of Reflective Roof Retrofit Field Tests
Energy use (kWh/day)
Reduction in utility
coincident peak demand (5-6 pm)
Test Site and Description
Albedo before
Albedo after
Before
After
Savings
Site #0 Merritt Island Cooling coating on
asphalt shingles, concrete block with
R-25 ceiling insulation, attic duct
system
0.22
0.73
38.7
34.7
4.0 (11%)
Not Measured
Site #1 Cocoa Beach Cooling coating on
asphalt shingles and flat gravel, R-11attic insulation, attic duct
system
0.21
0.73
40.6
30.3
10.3 (25%)
661 W (28%)
Site #2 Cocoa Beach cooling coating on tar paper;
flat roof and no
attic insulation, attic duct system
0.20
0.73
35.5
20.1
15.4 (43%)
858 W (38%)
Site #3 West Florida Cooling coating on
asphalt shingles, no attic insulation,
no attic duct system
0.08
0.61
22.4
16.8
5.6 (25%)
496 W (30%)
Site #4 Miami cooling coating for gravel roof, R-11
attic insulation,
attic duct system
0.31
0.61
51.9
43.9
8.0 (15%)
444 W (16%)
Site #5 Merritt Island Cooling coating on tile roof,
R-7 attic
insulation, attic duct system
0.20
0.64
57.5
45.9
11.6 (20%)
988 W (23%)
Averages
0.20
0.68
41.1
31.5
9.2 (23%)
683 W (27%)
How Long Will It Last?
Degradation of reflective roof coatings is of
practical concern because their high-albedo property is primarily
responsible for the cooling-energy savings. Cooling roof coatings may
have good longevity when applied properly. For example, a five-year old
swatch of an elastomeric coating applied to the cupola roof of the
FSEC`s Passive Cooling Laboratory still showed a laboratory reflectance
of 0.73--very close to the initial properties of such samples
(0.70-0.79) The reflectivity of the roofs in FSEC's experimental homes
was measured seven months after the coatings were applied. Some minor
stains due to disintegrated leaves and dust were evident at Site #1,
whereas no signs of degradation were in evidence on the flat roof at
Site #2. The average of the measurements at Site #1 indicated a
reflectance of 0.69 with greater variation in the readings over the roof
surface. The tested reflectance at Site #2 was 0.73. Although both aged
values were lower, a statistical test of the means revealed no
significant differences in the data taken immediately after the coating
were applied and those obtained seven months later. More recently,
however, FSEC examined the roofs at Sites #1 and #2--18 months after
they were coated. Although the flat roof at Site #2 still showed little
sign of weathering, some staining was becoming apparent on the coated
asphalt shingles at Site #1.
The most significant research on the longevity of
cooling coated roofing systems was performed recently at LBL. This
research examined 26 spot measurements of aged "high albedo" roofs of
various types and found that most of the weathering and reduction in
solar reflectance occurred in the first year after application or even
within the first two months. For a gravel coating the albedo was reduced
by 8% over six years, but 6% of the drop occurred in the first year.
However, other reflective roofing types experienced reductions to albedo
of up to 24%. The LBL researchers also experimented with washing cooling
roofing systems, and found that it was possible to restore roofs to 90%
of their initial values.
Figure 1a. Air conditioner use and interior air temperature before
and after a cooling roof coating is applied at site #3.
Figure 1b. Temperatures before a cooling roof coating is applied
at site #3.
FSEC
Figure 1c. Temperatures after a cooling roof coating was applied
at site #3.
The above temperatures are in deg. F (Average about 74,5) this
relates to only 23,61 deg. celcius. Yet at these
only slightly above room temperature temperatures, there are
huge electrical savings in air conditioning
electrical consumption as seen below. In typical South
African conditions where temperatures indoors frequently
reach to over 30 deg. C the electrical savings are massive.
Bearing in mind that the higher the ambient temperatures
the more effective Sno-Cote becomes.
Temperatures are in deg. F. Attic air means ceiling void air.
Temperatures are in deg. F. Here the roof surface temperature
reaches 37 deg. C. In South Africa this can reach
to 65 deg. C ( 149 deg. F) This is where Sno-Cote truly comes into
it`s own resulting in impressive cost savings.
Estimated to be R1,50 per deg. temp. difference per hour per 100
square meters of air-conditioned space.
Based on R1,56 per kwh. For a 60,000 square meter air-conditioned
shopping centre at a average temp drop of 5 deg. C
this equates to a saving of About R5,000-00 per hour.
Over a 5 year period, savings amount to R330-00 per square meter,
about 10 times the cost of the original coating contract.
Air Conditioning FAQ
Costs are in AUS$
Multiply by 7 for ZAR
Use a rule of thumb of about 600 Btu per
square meter of floor area to be air conditioned
9000 Btu of cooling output equates to 2.64
Kw of cooling wattage which requires 1000 watts of electrical input
which will cost about R0.75 cents per hour.
The above electrical consumption costs don`t
take into account maintenance or initial installation costs which can
increase the above savings by a factor of 3
1 Kg of air is about 850 liters in volume
The specific heat capacity of air is about 1
- i.e it requires about 1 KJ to heat 1 Kg of air by 1 deg.C
1 KJ is approx. .95 BTU
Air conditioning costs
calculator
Air conditionng electric running costs
http://michaelbluejay.com/electricity/cooling.html
The following are temperature recordings taken in Durban CBD on an
asbestos roof.
The ambient temperature was 30deg. C
TEMPERATURE RECORDINGS FOR COSMODEC PAINTED ROOF VS
NORMAL PAINTED ROOF ETHEKWINI MUNICIPALITY
DATES
AMBIENT
UNPAINTED ROOF
H&S OFFICES
COSMODEC PAINTED1ST
AID OFFICES
% LOWER COSMODEC
PAINTED ROOF
25/12/2010
25.33
30.5
26
14.75 %
26/12/2010
24.67
32
25.33
20.84 %
27/12/2010
29.33
42
30
28.57 %
28/12/2010
31.67
43.5
30.5
29.88 %
29/12/2010
31.33
43
30
30.23%
30/12/2010
29.33
34
27.33
19.62%
Temperatures are measured in degrees Celsius and readings recorded were
all at similar times ie within 10 minutes of one another. Temperature
sensors were placed in the ceilings of both H&S and First Aid buildings
on the OFP Complex and ambient temperatures measure D
in the
shade between the two buildings.
"Must it Be White?"
Many considering the potential of cooling roof
coatings are concerned about color. The FSEC has evaluated the
solar reflectance of some 37 different roofing materials, with the
measured data showing that white roof materials generally exhibit the
best performance. They are highly reflective across the solar spectral
bandwidth, while being highly emissive in the far-infrared region--this
is another way of saying they strongly reflect solar heat and any heat
they absorb will readily re-emit to the cooler sky temperatures. It may
seem a bit counter-intuitive, but
silver reflective aluminum paints do not perform nearly as well as
others. This is because, although the aluminum flake paints have a
high solar reflectance, they also have a low infrared emissivity--they
tend to hold whatever heat they absorb--negating the cooling
properties.
Fortunately, for those who demand non-white roof
colors, it appears possible to tailor paints and pigments so they are
not so reflective in the visible solar range, but are very reflective in
the "invisible" near infrared region. The Navy has conducted research in
this area to help develop infrared reflective coatings. Paints have been
created that are twice as reflective in the near infrared as in the
visible region. Researchers with LBL are examining spectrally selective
paints that offer the possibility of significantly increasing the solar
reflectance of even darkly pigmented colors. Physics suggests
green-colored pigments with large particle size may further enhance the
performance of solar reflective non-white paints. Even so, such coatings
will not likely perform better than materials that are uniformly very
reflective access the solar spectrum--particularly since the energy
intensity of solar radiation is greatest in the visible bandwidth.
Regardless, such developments promise to provide improved roofing
materials with high albedo, while still preserving the designer's
pallette of colors.
It may also be possible to tailor the properties
of white reflective coatings to create superior performance. An ideal
coating would be very reflective across the entire solar spectrum, while
being very emissive in the long infrared region so that heat is readily
re-emitted. Research shows promise in this area. One specialty coating,
used to coat astronomical observatory
domes , has a 98% solar reflectivity--so high that the temperature
of the material is only slightly higher than air temperature under
moderate solar intensity. Thus, it may be possible to tailor the
composition of roof coatings to further optimize their performance.
Asbestos roof on Food wholesaler
partially coated with Sno-Cote ®
showing before and after effects.
Cool contented pigs in a shed coated with Sno-Cote®
This drinks wholesaler in Zululand was
used to bottles exploding due to heat before Sno-Cote®,
now staff enjoy their lunch breaks in the warehouse.
These chickens look anything but
stressed because their farmer chose Sno-Cote ® .
Trials show that heat stress mortality
is all but eliminated with Sno-Cote ® .
Carrying capacity can be increased by
up to 20%
Storage Vessel
Factory
Paint ready for despatch
Partially coated factory roof
Nearing completion
Open ended factory benefiting from
Thermal insulation by means of a coating
Roof being high pressure
cleaned prior to coating
How Sno-Cote works
--------------------------------------------------------------------------------
"We tested these in Grahamstown yesterday (Hotter there than East London) and obtained
39 Deg. C beneath an uncoated sheet, 32 deg. C underneath the dark green and grey colours
and 31 deg. C underneath the white and light green colours"
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