1、Designation: E1185 15Standard Guide forSelecting Economic Methods for Evaluating Investments inBuildings and Building Systems1This standard is issued under the fixed designation E1185; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide identifies types of building design andbuilding system decisions that require economic analys
3、is andrecommends ASTM practices, adjuncts, and computer pro-grams that may be used to implement the appropriate economicmethods for each decision type.2. Referenced Documents2.1 ASTM Standards:2E631 Terminology of Building ConstructionsE833 Terminology of Building EconomicsE917 Practice for Measurin
4、g Life-Cycle Costs of Buildingsand Building SystemsE964 Practice for Measuring Benefit-to-Cost and Savings-to-Investment Ratios for Buildings and Building SystemsE1057 Practice for Measuring Internal Rate of Return andAdjusted Internal Rate of Return for Investments inBuildings and Building SystemsE
5、1074 Practice for Measuring Net Benefits and Net Savingsfor Investments in Buildings and Building SystemsE1121 Practice for Measuring Payback for Investments inBuildings and Building SystemsE1369 Guide for Selecting Techniques for Treating Uncer-tainty and Risk in the Economic Evaluation of Building
6、sand Building Systems2.2 Adjuncts:Discount Factor Tables Adjunct to Practices E917, E964,E1057, E1074, and E112133. Terminology3.1 DefinitionsFor definitions of general terms related tobuilding construction used in this guide, refer to TerminologyE631; and for general terms related to building econo
7、mics,refer to Terminology E833.4. Significance and Use4.1 Standard practices for measuring the economic perfor-mance of investments in buildings and building systems havebeen published by ASTM. A computer program that produceseconomic measures consistent with these practices is avail-able.4Discount
8、Factor Tables has been published by ASTM tofacilitate computing measures of performance for most of thepractices.4.2 This guide can be used to: (1) identify types of buildingdesign and system decisions that require economic analysis; (2)match the technically appropriate economic methods with thedeci
9、sions; and (3) locate the methods in the ASTM practicesand adjuncts listed in Section 2.4.3 More than one method can be technically appropriatefor many building decisions. Therefore the choice in practiceof which technically appropriate economic method to use forevaluating a particular building deci
10、sion will often depend onthe perspective of the user. Some examples of factors thatinfluence the user are: (1) ease of applying the methods, (2)level of familiarity of the user with the methods, (3) preferenceof the user for different methods, and (4) presence of budgetlimitations for the projects.4
11、.4 This guide identifies some features and limitations of themethods that might influence users choices under varyingconditions.5. How to Use This Guide5.1 Table 1 indicates which standard practices (that is,economic methods) are technically appropriate for the follow-ing four types of building inve
12、stment decisions: acceptance/rejection, design, size, and priority.5.1.1 In the context of this guide, an acceptance/rejectiondecision pertains to the cost effectiveness of an individualbuilding or building system. This type of decision is made1This guide is under the jurisdiction of ASTM Committee
13、E06 on Performanceof Buildings and is the direct responsibility of Subcommittee E06.81 on BuildingEconomics.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1987. Last previous edition approved in 2012 as E1185 12. DOI:10.1520/E1185-15.2For referenced ASTM standar
14、ds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from ASTM International Headquarters. Order Adjunct No.ADJE091703.4The NIST Bu
15、ilding Life-Cycle Cost (BLCC) Computer Program helps userscalculate measures of worth for buildings and building components that areconsistent with ASTM standards. The program is downloadable from http:/energy.gov/eere/femp/building-life-cycle-cost-programs.Copyright ASTM International, 100 Barr Har
16、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1independently of other project evaluations. It focuses on themerits of a single choice rather than on determining the mostcost-effective design or size.5.1.2 A design decision pertains to choices among compet-ing designs for an
17、individual building or building system,where only one design can be chosen.5.1.3 A sizing decision pertains to choices among compet-ing sizes or investment levels for an individual building orbuilding system, where only one size or level can be chosen.5.1.4 A ranking decision entails choosing one or
18、 moreprojects from a group of cost-effective projects when theavailable budget is not sufficient to fund them all.5.1.5 Examine Table 1 to find which methods should beconsidered for a given decision. The ASTM designations aregiven in parentheses under the method names.5.2 If there is any doubt as to
19、 which type of buildingdecision shown in Table 1 best applies, consult the examples inTable 2. Table 2 lists examples for each of the four types ofdecisions shown in Table 1. Find in Table 2 a building decisionsimilar to the one being analyzed, and select the correspondingdecision type from Table 1.
20、 Section 6 contains illustrative casesof this process.5.3 Once the type of decision has been identified and Table1 has been consulted for the technically appropriate method,there will be several methods from which to choose. Note thatwhile all of the methods that are marked as appropriate for agiven
21、 decision will generally give answers that support thesame decision (with the exception of payback), there are likelyto be special considerations that make one or more methodspreferred over the others. Examine the special considerationslisted in Table 3 before making a final choice of methods.5.4 Ex
22、amine the practice(s) that corresponds to the chosenmethod(s). In the selected practice(s), read the sections onsignificance and use, applications, and limitations. If thepractice(s) still seems appropriate, follow its procedures. If not,repeat the process using Tables 1 through 3 until an acceptabl
23、epractice has been found or it has been determined that none ofthe practices is suitable for the decision at hand.5.5 For assistance in calculating the measure(s) of economicperformance provided by the selected method(s), use theadjunct and the Building Life-Cycle Cost Computer Program(BLCC).4The ad
24、junct on Discount Factor Tables supportsmanual calculations for all of the methods. The BLCC supportscomputer calculations for all the methods except net benefitswhere revenues are involved and payback.6. Illustrative Cases6.1 Section 6 illustrates how to use this guide to choose theappropriate prac
25、tice for each of the four types of buildinginvestment decisions listed in Table 2.TABLE 1 Standard Practices For Making Building DecisionsAType ofBuildingDecisionApplicable StandardsLCC(PracticeE917)BCR(SIR)(PracticeE964)IRR(AIRR)(PracticeE1057)NB(NS)(PracticeE1074)PB(PracticeE1121)Accep-tance orrej
26、ectionBBBBCDesignBDDBESizePriority orrankingEBBEEAAll of the practices require discounting operations, but only Practice E917explains discounting in detail. All of the methods can be applied using techniquesfor treating uncertainty and risk. Practice E917 discusses briefly some of thesetechniques. T
27、he other practices do not discuss them. Guide E1369 coverstechniques for treating uncertainty in input variables to an economic analysis of abuilding investment project; it also recommends techniques for evaluating the riskthat a project will have a less favorable economic outcome than what is desir
28、ed orexpected.BTechnically appropriate standard practice when total discounted benefits (sav-ings) and costs are considered.CNote limitations in Table 3.DTechnically appropriate standard practice when incremental discounted benefits(savings) and costs are considered.ENot recommended.TABLE 2 Examples
29、 of Building Investment DecisionsType of Building Decision ExamplesAcceptance or rejection A.1 Is a water heater insulation kit cost effective?A.2 Are fire sprinklers cost effective?A.3 Is a given control system cost effective for managing HVAC equipment?A.4 Is a solar hot water system cost effectiv
30、e?Design D.1 Is single, double, or triple glazing most cost effective?D.2 What heating system is most cost effective?D.3 Which orientation of a building is most cost effective?D.4 Which code-approved plumbing system is most cost effective?D.5 Which wall type (for example, masonry, wood frame, curtai
31、n wall) is most cost effective?D.6 What floor finish (for example, carpeting, tile, wood) is most cost effective?D.7 What kind of insulation (for example, cellulose, fiberglass, rigid foam) is most cost effective?D.8 Is an item with low first costs more cost effective than a more durable substitute
32、with higher first costs?Size S.1 What is the economically efficient level (Rvalue) of insulation in the walls and above the ceiling of ahouse?S.2 How many square feet of collector area should be installed in a solar energy system?S.3 What heat pump efficiency (for example, HSPF 1.75, 2.0, 2.25) is m
33、ost cost effective?S.4 What furnace efficiency (for example, AFUE 60 %, 75 %, 90 %) is most cost effective?S.5 What air conditioner efficiency (for example, SEER 7.0, 9.0, 11.0) is most cost effective?Priority or ranking P.1 What combination of investments in a given building (for example, new water
34、 heater, new floor tile,and new lighting system) is economically preferred when each is justifiable on economicgrounds, but insufficient funds are available to pay for all of them?E1185 1526.2 Acceptance or Rejection Decisions:6.2.1 If it is known (by recognition of the type of decisionor by having
35、examined examples in Table 2) that the buildingdecision to be made is one of accepting or rejecting anindividual project, then a choice must be made from the fivepractices listed in Table 1. To illustrate how such a choicemight be made, an accept/reject building decision is evaluatedin terms of the
36、special considerations in Table 3.6.2.2 An example of an accept/reject building decision iswhether to install a programmable time clock to controlheating, ventilating, and air conditioning (HVAC) equipment ina commercial building. The time clock would reduce electricityconsumption by turning on only
37、 that part of the HVACequipment that is needed during hours when the building is notoccupied. Each of the five practices indicated in Table 1 for thistype of decision is examined to see how useful it would be inassessing the cost effectiveness of the time clock.6.2.3 The first method indicated in Ta
38、ble 1 is life-cycle cost(LCC). Life-cycle costs are the sum over a given study periodof the costs of initial investment (less resale value),replacements, operations (including energy use), and mainte-nance and repair of an investment decision (expressed inpresent or annual value terms). Table 3 show
39、s that the LCCmethod provides a dollar measure. Thus if decision makerswant a dollar measure of cost effectiveness, LCC would meetthat criterion. Table 3 also shows that the LCC method is mostuseful where cash flows are primarily costs. If the principalitems affected by the time clock are increased
40、capital costs forthe time clock and reduced energy costs, then the LCC methodwould be appropriate.6.2.3.1 To determine if the time clock is cost effective inaccordance with the LCC method, the LCC of providingheating and cooling without the time clock would be comparedagainst the LCC of heating and
41、cooling with the time clock,where the costs of the time clock and its associated energycosts are included. On economic grounds, the time clock wouldbe acceptable if its LCC were less than the LCC without it.6.2.3.2 Note that the LCCs for each alternative (as discussedin limitations in Table 3) must
42、be computed to make the LCCcomparison. Note further that the two alternatives must becompared for the same period of time for the LCC comparisonto be valid.6.2.4 The second method indicated in Table 1 is the benefit-to-cost ratio (BCR) or savings-to-investment ratio (SIR). Table3 shows this to be a
43、dimensionless ratio of project benefits orsavings to project costs. Benefits (savings) and costs areneeded to calculate this ratio. In evaluating the time clockinvestment, the problem must be structured so that the energycost reductions from having the time clock are expressed asbenefits or savings
44、and are compared against the associatedincreased capital cost. If the savings from the time clockexceed its associated costs (for example, if the SIR 1.0), thenthe time clock is cost effective.6.2.5 The third method in Table 1 is the internal rate ofreturn (IRR). This is the only method in Table 3 t
45、hat providesa rate-of-return measure in percentage terms. To use the IRR toevaluate the time clock investment, savings and cost data areneeded. The IRR is that rate of interest that discounts the futurestream of cash flows (net savings in this case) to a sum that justequals the investment cost of th
46、e time clock. If the IRR isgreater than the minimum acceptable rate of return to theinvestor (MARR), then the time clock is cost effective.NOTE 1The Internal Rate of Return of Practice E1057 defines twoIRR measures: the unadjusted IRR (UIRR) and the adjusted IRR (AIRR).The UIRR measure assumes that
47、the net cash flows are reinvested at a rateequal to that earned on the original investment, whereas the AIRRmeasure assumes that the net cash flows are reinvested at a rate differentfrom that earned on the original investment. The AIRR measure willsupport the same answer to a given building decision
48、 as the other methodslisted in Table 1 for that type of building decision. The UIRR measure willnot always support the same answer. In addition, the UIRR methodsometimes yields multiple solutions and therefore gives no clear answer asto whether the time clock is cost effective.6.2.6 The fourth metho
49、d in Table 1 is net benefits (NB). Ifthe benefits (savings) from the time clock exceed its cost, thenNB 0, and the time clock is cost effective.6.2.7 The fifth method shown in Table 1 is payback (PB). Itcalculates the time to recover investment costs using benefits(savings) and cost data. PB for the time clock is the number ofTABLE 3 Special ConsiderationsMethodUnit Measure of CostEffectivenessNature of Cash Flows LimitationsLCC $ primarily costs A single LCC measure gives no indication of economic merit of a building orbuilding component. LCC value for two or more alternatives
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