1、Designation: E1185 12Standard 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 in Build-ings and Building System
5、sE1074 Practice for Measuring Net Benefits and Net Savingsfor Investments in Buildings and Building SystemsE1121 Practice for Measuring Payback for Investments inBuildings and Building Systems2.2 Adjuncts:Discount Factor Tables Adjunct to Practices E917, E964,E1057, E1074, and E112133. Terminology3.
6、1 DefinitionsFor definitions of general terms related tobuilding construction used in this guide, refer to TerminologyE631; and for general terms related to building economics,refer to Terminology E833.4. Significance and Use4.1 Standard practices for measuring the economic perfor-mance of investmen
7、ts in buildings and building systems havebeen published by ASTM. A computer program that produceseconomic measures consistent with these practices is avail-able.4Discount Factor Tables has been published by ASTM tofacilitate computing measures of performance for most of thepractices.4.2 This guide c
8、an be used to: (1) identify types of buildingdesign and system decisions that require economic analysis; (2)match the technically appropriate economic methods with thedecisions; and (3) locate the methods in the ASTM practicesand adjuncts listed in Section 2.4.3 More than one method can be technical
9、ly appropriatefor many building decisions. Therefore the choice in practiceof which technically appropriate economic method to use forevaluating a particular building decision will often depend onthe perspective of the user. Some examples of factors thatinfluence the user are: (1) ease of applying t
10、he 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.4.4 This guide identifies some features and limitations of themethods that might influence users choices under varyingconditions.5
11、. 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 investment decisions: acceptance/rejection, design, size, and priority.5.1.1 In the context of this guide, an acceptance/rejectiondec
12、ision pertains to the cost effectiveness of an individualbuilding or building system. This type of decision is madeindependently of other project evaluations. It focuses on themerits of a single choice rather than on determining the mostcost-effective design or size.1This guide is under the jurisdic
13、tion of ASTM Committee E06 on Performanceof Buildings and is the direct responsibility of Subcommittee E06.81 on BuildingEconomics.Current edition approved April 1, 2012. Published April 2012. Originallyapproved in 1987. Last previous edition approved in 2007 as E1185 071. DOI:10.1520/E1185-12.2For
14、referenced ASTM standards, 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.
15、ADJE091703.4The NIST Building 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:/www.eere.energy.gov/femp/information/download_blcc.html.1Copyright ASTM In
16、ternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.2 A design decision pertains to choices among compet-ing designs for an individual building or building system,where only one design can be chosen.5.1.3 A sizing decision pertains to choices among co
17、mpet-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 moreprojects from a group of cost-effective projects when theavailable budget is not sufficient to fund them all.5.1.5 Examine
18、 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 which type of buildingdecision shown in Table 1 best applies, consult the examples inTable 2. Table 2 lists examples for each
19、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. Section 6 contains illustrative casesof this process.5.3 Once the type of decision has been identified and Table1 has been con
20、sulted 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 decision will generally give answers that support thesame decision (with the exception of payback), there are likelyto be spec
21、ial 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 Examine the practice(s) that corresponds to the chosenmethod(s). In the selected practice(s), read the sections onsignificance an
22、d 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 acceptablepractice has been found or it has been determined that none ofthe practices is suitable for the decision at hand.5.5 For assis
23、tance 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 adjunct on Discount Factor Tables supportsmanual calculations for all of the methods. The BLCC supportscomputer calculations for
24、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 practice for each of the four types of buildinginvestment decisions listed in Table 2.6.2 Acceptance or Rejection Decisions:6.2.1 I
25、f it is known (by recognition of the type of decisionor by having 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 mad
26、e, an accept/reject building decision is evaluatedin terms of the 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 inTABLE 1 Standard Practices
27、 For Making Building DecisionsAType ofBuildingDecisionApplicable StandardsLCC(PracticeE917)BCR(SIR)(PracticeE964)IRR(AIRR)(PracticeE1057)NB(NS)(PracticeE1074)PB(PracticeE1121)Acceptanceor rejectionBBBBCDesignBDDBESizePriority orrankingEBBEEAAll of the practices require discounting operations, but on
28、ly 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. The other practices do not discuss them.BTechnically appropriate standard practice when total discounted benef
29、its(savings) and costs are considered.CNote limitations in Table 3.DTechnically appropriate standard practice when incremental discounted ben-efits (savings) and costs are considered.ENot recommended.TABLE 2 Examples of Building Investment DecisionsType of Building Decision ExamplesAcceptance or rej
30、ection 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 effective?Design D.1 Is single, double, or triple glazing most cost effective?D.2 What heati
31、ng 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, curtain wall) is most cost effective?D.6 What floor finish (for example, carpeting, tile,
32、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 with higher first costs?Size S.1 What is the economically efficient level (Rvalue) o
33、f insulation in the walls and above the ceiling of a house?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 most cost effective?S.4 What furnace efficiency (for example, AFUE 60 %, 75 %, 90 %)
34、 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 heater, new floor tile,and new lighting system) is economically preferred when eac
35、h is justifiable on economicgrounds, but insufficient funds are available to pay for all of them?E1185 122a commercial building. The time clock would reduce electricityconsumption by turning on only that part of the HVACequipment that is needed during hours when the building is notoccupied. Each of
36、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 Table 1 is life-cycle cost(LCC). Life-cycle costs are the sum over a given study periodof the costs of i
37、nitial investment (less resale value), replace-ments, operations (including energy use), and maintenance andrepair of an investment decision (expressed in present orannual value terms). Table 3 shows that the LCC methodprovides a dollar measure. Thus if decision makers want adollar measure of cost e
38、ffectiveness, LCC would meet thatcriterion. 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 capital costs forthe time clock and reduced energy costs, then the LCC methodwould be appropriate.6.2.
39、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 cooling with the time clock,where the costs of the time clock and its associated energycosts are inclu
40、ded. 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 be computed to make the LCCcomparison. Note further that the two alternatives must becompared for the
41、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 dimensionless ratio of project benefits orsavings to project costs. Benefits (savings) and costs arene
42、eded 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 and are compared against the associatedincreased capital cost. If the savings from the time clockexcee
43、d 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 that providesa rate-of-return measure in percentage terms. To use the IRR toevaluate the time clock inv
44、estment, 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 the time clock. If the IRR isgreater than the minimum acceptable rate of return to theinvestor (MARR), t
45、hen 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 the net cash flows are reinvested at a rateequal to that earned on the original investment, whereas th
46、e 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 as the other methodslisted in Table 1 for that type of building decision. The UIRR measure willnot al
47、ways 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 method in Table 1 is net benefits (NB). Ifthe benefits (savings) from the time clock exceed its cost, thenN
48、B 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 ofyears required for savings from reduced energy costs to justequal the inve
49、stment costs of the time clock. If PB (forexample, three years) is equal to or less than the maximumacceptable payback period (for example, six years), the timeclock will satisfy the payback criterion for acceptability.However, the limitations section of Table 3 indicates that PB isa misleading measure of cost effectiveness because it ignorescash flows beyond the payback year and, in the case of simpleTABLE 3 Special ConsiderationsMethodUnit Measure of CostEffectivenessNature of Cash Flows LimitationsLCC $ primarily costs A single LCC measure gives no indication of economic mer
