For: Tech Traders
By: H. F. Poppendiek
April 2003
GEOSCIENCE LTD
6260 Marindustry Drive
San Diego, California 92121
Download PDF
- INTRODUCTION
- MATHEMATICAL THERMAL WALL OR ROOF MODEL
- THE EXPERIMENTAL SYSTEM
- THE TEST PROCEDURE
- TEST RESULTS
- CONCLUDING COMMENTS
- SYNOPSIS (From Tech Traders)
Photograph of the solar lamp array and Insuladd painted wall panel
Photograph of the millivolt recorder and solar lamp array
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.
Top
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
Top
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.
Top
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.
Top
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).
Top
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.
Top
SYNOPSIS (From Tech Traders)
The following table shows the effective “R” values for common wall types.
As you can see from the test report by Geoscience Labs, the use of Insuladd® can dramatically increase the effective “R”value of these common wall types by over 50%!
Top
A Study of the Energy Savings that can Occur when Using Insuladd Solar Reflective Paint on Irradiated Building Walls
PDF (Right click and choose "Save Target As" to download, or click to view)
PDF Requires Acrobat Reader (free)
 |
|
