This paper describes a transient heat and mass transfer model of residential attics. The model is used to predict hourly ceiling heat gain/loss in residences with the purpose of estimating reductions in cooling and heating loads produced by radiant barriers. The model accounts for transient conduction, convection, and radiation and incorporates moisture and air transport across the attic. Environmental variables, such as solar loads on outer attic surfaces and sky temperatures, are also estimated. The model is driven by hourly weather data which include: outdoor dry bulb air temperature, horizontal solar and sky radiation, wind speed and direction, relative humidity (or dew point), and cloud cover data. The output of the model includes ceiling heat fluxes, inner and outer heat fluxes from all surfaces, inner and outer surface temperatures, and attic dry bulb air temperatures. The calculated fluxes have been compared to experimental data of side-by-side testing of attics retrofit with radiant barriers. The model predicts ceiling heat flows with an error of less than ten percent for most cases.

Issue Section:
Research Papers
Topics:
Heat, Mass transfer, Transients (Dynamics), Temperature, Ceilings, Flux (Metallurgy), Radiation (Physics), Solar energy, Stress, Commercial air transport, Convection, Errors, Flow (Dynamics), Heating and cooling, Testing, Transient heat transfer, Wind velocity
1.
ASHRAE, 1989, Handbook of Fundamentals, ASHRAE, Atlanta, GA.
2.
Burch
D. M.
,
Lemay
M. R.
,
Rian
B. J.
, and
Parker
E. J.
,
1984
, “
Experimental Validation of an Attic Condensation Model
,”
ASHRAE Transactions
, Vol.
20
, Part 2A, pp.
59
–
77
.
3.
Chen
T. S.
,
Armaly
B. F.
, and
Ramachandran
N.
,
1986
, “
Correlations for Laminar Mixed Convection Flows on Vertical, Inclined, and Horizontal Flat Plates
,”
ASME Journal of Heat Transfer
, Vol.
108
, pp.
835
–
840
.
4.
Churchill
S. W.
,
1977
, “
A Comprehensive Correlating Equation for Laminar Assisting, Forced and Free Convection
,”
AIChE Journal
, Vol.
23
, pp.
10
–
16
.
5.
Churchill
S. W.
, and
Chu
H. H. S.
,
1975
, “
Correlating Equations for Laminar and Turbulent Free Convection from a Vertical Plate
,”
International Journal of Heat and Mass Transfer
, Vol.
18
, p.
1323
1323
.
6.
Cleary
P. G.
,
1985
, “
Moisture Control by Attic Ventilation—An In-Situ Study
,”
ASHRAE Transactions
, Vol.
91
, Part 1, pp.
227
–
239
.
7.
Duffie, J. A., and Beckman, 1974, Solar Thermal Energy Processes, John Wiley and Sons, New York.
8.
Hamilton, D. C., and Morgan, W. R., 1952, “Radiant Interchange Configuration Factors,” NACA TN 2836.
9.
Incropera, F. P., and Dewitt, D. P., 1981, Fundamentals of Heat Transfer, John Wiley and Sons, New York.
10.
Martin
A.
, and
Berdahl
,
1984
, “
Characteristics of Infrared Sky Radiation in the United States
,”
Solar Energy
, Vol.
33
, pp.
321
–
336
.
11.
Mitalas, G. P., and Stephenson, D. G., 1967, “Room Thermal Response Factors,” ASHRAE Transactions, Vol. 73, Part I.
12.
Peavy, B. A., 1979, “A Model for Predicting the Thermal Performance of Ventilated Attics,” Summer Attic and Whole House Ventilation, NBS SP 548, Washington D.C.
13.
Sherwood, T. K., and Pigford, R. L., 1952, Absorption and Extraction, McGraw-Hill, New York.
14.
Sparrow, E. M., and Cess, R. D., 1970, Radiation Heat Transfer, Brooks/Cole Publishing Co., Belmont, CA.
15.
Wilkes, K. E., 1989, “Modeling of Residential Attics with Radiant Barriers,” Proceedings of the Fifth Annual Symposium on Improving Building Energy Efficiency In Hot and Humid Climates, Houston, TX, pp. 161–168.
16.
Wilkes, K. E., 1991, “Analysis of Annual Thermal and Moisture Performance of Radiant Barrier Systems,” ORNL/CON-319, Oak Ridge National Laboratory, Oak Ridge, TN.
This content is only available via PDF.
Copyright © 1998
 by The American Society of Mechanical Engineers
You do not currently have access to this content.