THE STUDY INVOLVED AN ANALYSIS OF VARIOUS WALLS IN 10 CLIMATIC CONDITIONS USING WEATHER TAPES FROM 10 CITIES COVERING A 10-YEAR PERIOD. MASONRY ENGINEERS SPECIFIED 10 WALLS FOR THE STUDYING RANGING IN MASS FROM 4 TO 116 POUNDS PER SQUARE FOOR AND WITH 'U,' OR (WALL HEAT-TRANSFER RESISTANCE,) VALUES RANGING FROM 0.07 TO 0.27. THERMAL PERFORMANCE OF EACH WALL WAS ANALYZED IN EACH OF THE 10 CITIES AND IN 8 ORIENTATIONS--NORTH, NORTHEAST, EAST, SOUTHEAST, SOUTH, SOUTHWEST, WEST, AND NORTHWEST--FOR 24 HOURS A DAY. A YEAR WHICH MOST CLOSELY TYPIFIED ALL 10 YEARS WAS SELECTED AS THE DESIGN YEAR. ONE DAY WAS STATISTICALLY DEVELOPED AND SELECTED TO TYPIFY EACH MONTH OF THE DESIGN YEAR. THE STUDY CONCLUDED THAT THE TRADITIONAL METHOD OF CALCULATING HEAT LOSS DID NOT CONSIDER ALL THE VARIABLES INVOLVED IN HEAT FLOW THROUGH BUILDING ENVELOPES AND THAT THIS METHOD ASSUMED A STEADY-STATE HEAT FLOW THAT DISREGARDED THE EFFECTS OF MASS. THE COMBINED INFLUENCE OF RESISTANCE AND CAPACITY INSULATION ACTUALLY DETERMINED BUILDING REGULATION OF HEAT GAIN AND LOSS. ALSO, THE CAPACITY INSULATION OF A BUILDING ELEMENT DEPENDED LARGELY ON THE WEIGHT OR MASS OR THE ELEMENT--THE HEAVIER THE ELEEMNT, THE MORE HEAT IT COULD RETAIN. FINALLY, THE 'M' FACTOR THAT WAS DEVELOPED--A DIMENSIONLESS CORRECTION FACTOR--OFFERED A SIMPLE APPROACH FOR A REALISTIC PEAK LOAD CALCULATION. TABULAR DATA INCLUDING CHARTS AND GRAPHS, AN ARTICLE ON THE 'M' FACTOR, AND AN 'M' FACTOR BUILDING CODE REFERENCE ARE PROVIDED. (AOP)