Calculation of Equivalent “R-value”
These calculations arebased on the following report:
A Study of the EnergySavings that can Occur when Using Insuladd Solar Reflective Paint on Irradiated Building Walls
As conducted by Dr. H. F.PoppendiekGEOSCIENCE LTD
6260 Marindustry Drive
SanDiego, California 92121
April 2003
Thefollowing calculation was carried out by engineers at M. J. TradingInternational, Inc., for Tech Traders, Inc. The purpose of this report is tocalculate out how the equivalent “R-value,”as derivedfrom the application of INSULADD added into ordinary paint. Geoscience calculated an equivalent “R”of “6” in the followingreport.
Ourcalculation is given below:
qcooling / A = (t - ti) / (Rr + Ri) …………………… (2)
* Heat flux without INSULADD application – fromthe report.
- Measured = 5.24
* Heat flux with INSULADD application –from the report.
- Measured = 3.57
- Calculated = 3.53 (using Equation(1) in the report)
-Very good agreement!
*The reasoning is that the reduction of heat flux from the application ofINSULADD-added paint (from 5.24 down to 3.53), may be viewed as the result of awall that has a higher value of thermal resistance than the R-value it has now.This additional thermal resistance may be calculated using Equation (2) aboveand the experimental data given in the report as shown below:
qcooling/ A = (t - ti) / (Rr + Ri)
(t - ti) / (Rr + Ri + R) = 3.53
Where,
t =Irradiated wall temperature = 141.8oF
ti = Invariantinterior air temperature of building = 75.8 oF
Rr =Thermal resistance of wall = 12 hr-ft2-oF/Btu
Ri = Interior air resistance = 1 hr-ft2-oF/Btu
R = The additional thermal resistance, or the equivalent “R”
Thus
(141.8– 75.8) / (12 + 1 + R) = 3.53
(3.53)(R + 13) = 66
(R + 13) = 66 / 3.53 = 18.7
R = 5.7
Note that instead of using thecalculated reduced heat flux of 3.53, we may use the measured value at 3.57. Ifso, then the equivalent “R” would be 5.5.
Thus, using this process as describedin the report, yielded an “R = 5.5 to 5.7”.
IThis process of deriving anequivalent thermal resistance value is correct.
We are able to do the same on the testsTech Traders did in late last March using an ESP board with a “R = 3 valueshown below.
---------------------------------------------------------------------------------------------------------------- Infrared Heat lamp tests of R-3 foampanels and Insuladd insulating paint additive mixed into latex primer.
3/19/07
A series of 6 testswere performed using a 450 watt heat lamp array positioned 18” from theexterior of 20” x 20” pieces of standard foam home insulation R-3 rated panels.
One panel was paintedon one side with one coat of inexpensive latex primer to which Insuladdinsulating additive for paint had been added. The coverage rate was based on225 to 250 sq ft per gallon of primer.
The second panel wasleft uncoated.
During the tests eachpanel was covered on the side exposed to the heat lamp array with dark brownfabric to enhance heat gain and to negate the inherent reflective properties ofthe panels.
Each panel beingtested had a heat flux transducer attached to the backside of the panel. Eachpanel was then attached with an airtight seal to a 16” x 16” x 13” insulatedchamber and exposed to the infrared heat lamp array for 30 minutes by whichtime the heat flux had stabilized and no increases were occurring.
The exterior surfacetemperature of the dark brown fabric covered R-3 panel averaged 180 Fthroughout all of the tests. Ambient airtemperature was 89 deg. F
The tests were run 6times and the results of the tests were averaged to get the following results:
Uncoated R-3 panel: Heat Flux was measured at 25.8 BTU per hour per Ft (squared)
R-3 panel coated on exterior: (heat side) with Insuladd insulating additive for house paint: Heat Flux was measured at 17.2 BTU perHour per Ft (squared)
Summary: The Insuladd/Primer coated panelconsistently produced results showing a reduced heat flux through the R-3 panelof 33%.
Infrared Heat lamp tests of R-3 foampanels and Insuladd insulating paint additive mixed into latex primer.
3/19/07
A series of 6 testswere performed using a 450 watt heat lamp array positioned 18” from theexterior of 20” x 20” pieces of standard foam home insulation R-3 rated panels.
One panel was paintedon one side with one coat of inexpensive latex primer to which Insuladdinsulating additive for paint had been added. The coverage rate was based on225 to 250 sq ft per gallon of primer.
The second panel wasleft uncoated.
During the tests eachpanel was covered on the side exposed to the heat lamp array with dark brownfabric to enhance heat gain and to negate the inherent reflective properties ofthe panels.
Each panel beingtested had a heat flux transducer attached to the backside of the panel. Eachpanel was then attached with an airtight seal to a 16” x 16” x 13” insulatedchamber and exposed to the infrared heat lamp array for 30 minutes by whichtime the heat flux had stabilized and no increases were occurring.
The exterior surfacetemperature of the dark brown fabric covered R-3 panel averaged 180 Fthroughout all of the tests. Ambient airtemperature was 89 deg. F
The tests were run 6times and the results of the tests were averaged to get the following results:
Uncoated R-3 panel: Heat Flux was measured at 25.8 BTU per hour per Ft (squared)
R-3 panel coated on exterior: (heat side) with Insuladd insulating additive for house paint: Heat Flux was measured at 17.2 BTU perHour per Ft (squared)
Summary: The Insuladd/Primer coated panelconsistently produced results showing a reduced heat flux through the R-3 panelof 33%.
