LIFE-CYCLE COST (LCC) ANALYSIS HELPS IN DECIDING IF IT IS WORTH INVESTING EXTENSIVE MONIES NOW IN ORDER TO AVOID INCURRING HIGHER OPERATING OR MAINTENANCE COSTS LATER. THE ANALYZER CHOOSES WHICH ELEMENTS WILL BE THE CONSTANTS AND WHICH THE PARAMETERS OR ELEMENTS OF CHANGE IN THE ANALYSIS. IN ADDITION, THE PERIOD LENGTH MUST BE CHOSEN, THE COSTS AND BENEFITS OF THE CHANGES MEASURED AND QUANTIFIED, AND VARIOUS DESIGN OPTIONS FOR BOTH COSTS AND BENEFITS COMPARED. IN EXAMINING THE DEPARTMENT OF ENERGY (DOE) LIFE-CYCLE COST ANALYSIS FOR THE SINGLE FAMILY RESIDENCE, HOWEVER, CERTAIN CONDITIONS,--TRIPLE WINDOW GLAZING AND THERMOSTATS SET AT 70 DEGREES--ARE ASSUMED AS CONSTANTS. IN ADDITION, INFORMATION ON THE DOE PARAMETER RANGES AND THE DESIGNS THAT SHOULD RESULT FROM THESE CHOICES IS NOT AVAILABLE. DOE FURTHER ASSUMES THAT ALL OF THE FIXTURES THAT CONTRIBUTE SIGNIFICANTLY TO THE COST OF A HOUSE WILL NOT BE REPLACED FOR 30 YEARS AND DOES NOT TAKE THE INCREASED MARKET VALUE OF AN ENERGY CONSERVING HOUSE INTO ACCOUNT. DOE ALSO USES AN ADD-ON APPROACH WHICH MAKES CONSERVATION OPTIONS APPEAR MORE EXPENSIVE THAN THEY REALLY ARE. BEPS SHOULD BE SET AT THE LCC MINIMUM THAT ALSO PROVIDES BENEFITS WITHIN ACCEPTABLE COMFORT TOLERANCE LEVELS. TO ENCOURAGE MORE ENERGY EFFICIENCY, DOE NEEDS TO MAKE FURTHER REVISIONS TO ITS LCC WORK FOR SINGLE FAMILY RESIDENCES AND TO APPLY THE SAME PHILOSOPHY TO ALL OTHER BUILDINGS. (AOP)