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A Study of the Energy Savings that can
Occur when Using Insuladd Solar Reflective
Paint on Irradiated Building Walls
For
Tech Traders
By
H. F. Poppendiek
April 2003
GEOSCIENCE LTD
6260 Marindustry Drive
San Diego, California 92121
Photograph of the solar lamp array and Insuladd painted wall panel
Photograph of the millivolt recorder and solar lamp array
I. INTRODUCTION
Geoscience was requested by Mr. David Page to perform several tasks relative to the energy savings that result when
using Insuladd paint on the outside of the building envelope. One task dealt with comparative outer wall panel
surface temperature and corresponding heat flux measurements for the solar irradiated panels painted with Insuladd
paint as well as with ordinary paint. A second task involved determining the additional panel thermal resistances that
would have to be added to insulated wall systems painted with ordinary paint to yield the low thermal heat fluxes
through a building wall when using Insuladd paint on the outer surface. The last task that was requested involved
defining a mathematical thermal wall model so that the equations can be used to calculate wall thermal performance
characteristics when system parameter changes occur.
II. MATHEMATICAL THERMAL WALL OR ROOF MODEL
An elementary model has been used which gives the steady state wall or roof temperature and the required heat
removal to maintain a given room temperature when the outside weather conditions are known.
The heat balance for this system is,
Where
The equation used to determine the air conditioning load is,
Where
III. THE EXPERIMENTAL SYSTEM
A wall panel having an R value somewhat typical of a building wall, namely, R = 12 hr ft2 °F/Btu, was instrumented
with surface thermo-couples, as well as a large, thin calibrated heat flux transducer. The vertical test panel front
surface faced a battery of sun lamps that provided the simulated solar irradiation. The heat flux transducer was
located in the middle of the vertical panel. Heat absorbed on the front surface of the panel was lost 1) by conduction
through the panel into the air behind it and 2) by infrared radiation and natural air convection from the front surface
of the panel.
IV. THE TEST PROCEDURE
From the hot and cold panel surface temperatures, the front and back ambient air temperatures and the heat flow
transducer heat flux measurements, the system R values were determined.One set of measurements was made for the
Insuladd-applied paint and the other set for ordinary house paint.
From the two sets of data, one can obtain the energy savings and the additional thermal resistance that would have to
be added to the panel with ordinary paint to get the reduced heat flux attained by the panel with Insuladd added
paint.
V. TEST RESULTS
The test results for the insulation panel with its outer surface painted with Insuladd paint follow:
The test results for the insulation panel with its outer surface painted with ordinary (light green) latex house paint follow:
On the basis of these two sets of data, the energy savings obtained when using the Insuladd paint instead of an
ordinary paint is,
It is also pointed out that if one added an additional thermal resistance of Radd. = 6.0 hr ft2 °F/Btu to the wall system
having the ordinary house paint on its outer surface, the higher heat flux being conducted into the building, namely,
5.24 Btu/hr ft2 would be reduced to the lower heat flux value of 3.57 Btu/hr ft2 for the wall painted with Insuladd
paint. This additional resistance calculation is performed by a trial and error calculation using Equation (1) (by
iterating Rr, t and q/A).
VI. CONCLUDING COMMENTS
It is pointed out that the energy savings terms and add, values are not just functions of the solar reflectivities and IR
emissivities, but also of the Rr and system temperature information. It is also to be noted that ordinary paints can
have a range of solar reflectivities and IR emissivities, depending upon their chemical constituency.
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