Freon evaporation cycle are the same in a refrigerator as in an air conditioner.
According to the Merriam-Webster Dictionary Online, the term Freon is generically &used for any of various conditioner. According to the Merriam-Webster Dictionary Online, the term Freon is generically &used for any of various nonflammable
fluorocarbons used as refrigerants and as propellants for aerosols.&
This is how the evaporation cycle in an air conditioner works (See How
Refrigerators Work for complete details on this cycle):
1.The compressor compresses cool Freon gas, causing it to become hot,
high-pressure Freon gas (red in the diagram above).
2.This hot gas runs through a set of coils so it can dissipate its heat, and it
condenses into a liquid.
3.The Freon liquid runs through an expansion valve, and in the process it
evaporates to become cold, low-pressure Freon gas (light blue in the diagram above).
4.This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.
Mixed in with the Freon is a small amount of a light weight oil. This oil
lubricates the compressor.
Window Units
A window air conditioner unit implements a complete air conditioner in a small space. The units are made small enough to fit into a standard window frame. You close the window down on the unit, plug the unit in and turn it on to get cool air. If you take the cover off of an unplugged window unit, you will find that it contains:
A compressor
An expansion valve
A hot coil (on the outside)
A chilled coil (on the inside)
A control unit
The fans blow air over the coils to improve their ability to dissipate heat (to the outside air) and cold (to the room being cooled).
BTU and EER
Most air conditioners have their capacity rated in British thermal units (BTU). Generally speaking, a BTU is the amount of heat required to raise the temperature of one pound (0.45 kg) of water 1 degree Fahrenheit (0.56 degrees Celsius). Specifically, 1 BTU equals 1,055 joules. In heating and cooling terms, 1 &ton& equals 12,000 BTU.
A typical window air conditioner might be rated at 10,000 BTU. For comparison, a typical 2,000-square-foot (185.8 m2) house might have a 5-ton (60,000-BTU) air conditioning system, implying that you might need perhaps 30 BTU per square foot. (Keep in mind that these are rough estimates. To size an air conditioner for your specific needs, contact an HVAC contractor.)
The energy efficiency rating (EER) of an air conditioner is its BTU rating over its wattage. For example, if a 10,000-BTU air conditioner consumes 1,200 watts, its EER is 8.3 (10,000 BTU/1,200 watts). Obviously, you would like the EER to be as high as possible, but normally a higher EER is accompanied by a higher price.
Is the higher EER is worth it?
Let's say that you have a choice between two 10,000-BTU units. One has an
EER of 8.3 and consumes 1,200 watts, and the other has an EER of 10 and consumes 1,000 watts. Let's also say that the price difference is $100. To understand what the payback period is on the more expensive unit, you need to know:
1.Approximately how many hours per year you will be operating the unit
2.How much a kilowatt-hour (kWh) costs in your area
Let's say that you plan to use the air conditioner in the summer (four months a year) and it will be operating about six hours a day. Let's also imagine that the cost in your area is $0.10/kWh. The difference in energy consumption between the two units is 200 watts, which means that every five hours the less expensive unit will consume 1 additional kWh (and therefore $0.10 more) than the more expensive unit.
Assuming that there are 30 days in a month, you find that during the summer you are operating the air conditioner:
Since the more expensive unit costs $100 more that means that it will take about seven years for the more expensive unit to break even.
See this page for a great explanation of seasonal energy efficiency rating
Split-system Units
A split-system air conditioner splits the hot side from the cold side of the
The cold side, consisting of the expansion valve and the cold coil, is generally placed into a furnace or some other air handler. The air handler blows air through
ducts. The hot side known as the condensing unit, lives outside the building. The unit consists of a long, spiral coil shaped like a cylinder. Inside the coil is a fan, to blow air through the coil, along with a weather-resistant compressor and some control logic. This approach has evolved over the years because it is low-cost, and also because it normally results in reduced noise inside the house (at the expense of increased noise outside the house). Besides the fact that the hot and cold sides are split apart and the capacity is higher (making the coils and compressor larger), there is no difference between a split-system and a window air conditioner.
In warehouses, businesses, malls, large department stores, etc., the condensing unit normally lives on the roof and can be quite massive. Alternatively, there may be many smaller units on the roof, each attached inside to a small air handler that cools a specific zone in the building.
Let's take a look now at a chilled-water air conditioner.
Chilled-water System
In larger buildings and particularly in multi-story buildings, the split-system
approach begins to run into problems. Either running the pipe between the condenser and the air handler exceeds distance limitations (runs that are too long start to cause lubrication difficulties in the compressor), or the amount of duct -work and the length of ducts become unmanageable. At this point, it is time to think about a chilled-water system.
In a chilled-water system, the entire air conditioner lives on the roof or behind the building. It cools water to between 40 and 45 F (4.4 and 7.2 C). This chilled water is then piped throughout the building and connected to air handlers as needed. There is no practical limit to the length of a chilled-water pipe if the system can be got well -
Whenever you walk behind a building and find a unit that has large quantities of water running through a plastic mesh, you will know you have found a cooling tower!
In many office complexes and college campuses, cooling towers and air
conditioning equipment are centralized, and chilled water is routed to all of the buildings through miles of underground pipes.
Based on dynamic load track central air-conditioning system entire closed loop energy conservation technology research.
1. introductions
The energy conservation may say is the building character automatic control
system starting point and the home to return to. It is well known, in the intelligent
construction, HVAC (heating, ventilates and air conditioning) the system consumes to have to occupy the building consumption total energy enormous partial proportions, approximately about 50% ~60%. Specially cold: East the unit, the cooling tower, the circulating water pump and the air conditioning unit, the new atmosphere unit, all are consumes energy the big household. Therefore really has essential develops one effective air-conditioning system energy conservation method, especially uses is in improves in the existing building air-conditioning system automation the aspect. DDC (Directdigitalcontr01) the direct of numerical control, is a structure simple operation easy control device, it may borrow by the connection switches over the equipment to make the systems control along with the load change, like the air conditioning cold water circulatory system, the air conditioning box frequency conversion automatic amount of wind adjustment and the cooling tower radiation ventilator frequency conversion holds controls and so on, may let an air-conditioning system more
effective revolution, like this, not only brings the very big economic efficiency for the estate management, moreover also may cause the system to move under a better operating mode, thus lengthens the equipment the service life as well as achieved provides goal of the comfortable air conditioning environment and the energy conservation.
The general building commonly used air-conditioning system has CAV, VAV,4发现相似题项目管理中英文--成本估算
Cost Estimation
成 本 估 算
Costs Associated with Constructed
Facilities
与建筑设施相关的成本
The costs of a constructed facility to the owner include both
the initial capital cost and the subsequent operation and
maintenance costs. Each of these major cost categories consists of
a number of cost components.
对业主来说，一项建筑设施的成本包括初始投资和随后的运行与养护费用。这两大项费用又是由许多分项费用组成的。
The capital cost for a construction project
includes the expenses related to the initial establishment of the
对于一个建设项目，其初始投资包括与建设该设施相关的各项资本投入：
􀁺 Land acquisition, including holding and
improvement.
􀁺 取得土地，包括持有和再开发。
􀁺 Planning and feasibility studies.
􀁺 规划和可行性研究。
􀁺 Architectural and engineering design.
􀁺 建筑和工程设计。
􀁺 Construction, including materials, equipment and
􀁺 施工，包括材料、设备和劳动力。
􀁺 Field supervision of construction.
􀁺 现场施工监督。
􀁺 Construction financing.
􀁺 建设融资成本。
􀁺 Insurance and taxes during construction.
􀁺 建设过程中的各种保险和税费。
􀁺 Owner’s general office overhead.
􀁺 业主的一般行政管理开支。
􀁺 Equipment and furnishings not included in
construction.
􀁺 不包括在施工中的设备和家具。
􀁺 Inspection and testing.
􀁺 检查和试验。
The operation and maintenance cost in subsequent years over the
project life cycle includes the following expenses:
在项目建成后全寿命周期中的运行与维护费用包括以下几个方面：
􀁺 Land rent, if applicable.
􀁺 土地租金(如果有的话)。
􀁺 Operating staff.
􀁺 运行人员费用。
􀁺 Labor and material for maintenance and
􀁺 维修和保养的劳动力和材料费用。
􀁺 Periodic renovations.
􀁺 周期性翻新费用。
􀁺 Insurance and taxes.
􀁺 保险和税费。
􀁺 Financing costs.
􀁺 融资成本。
􀁺 Utilities.
􀁺 公用事业费。
􀁺 Owner’s other expenses.
􀁺 业主的其他开支。
The magnitude of each of these cost components depends on the
nature, size and location of the project as well as the management
organization, among many considerations. The owner is interested in
achieving the lowest possible overall project cost that is
consistent with its investment objectives.
以上这些费用的多少要由项目的性质、规模和地理位置，以及管理组织等多方面的因素来决定。业主总希望以尽可能少的投入来实现项目的目标。
It is important for design professionals and construction
managers to realize that while the construction cost may be the
single largest component of the capital cost, other cost components
are not insignificant. For example, land acquisition costs are a
major expenditure for building construction in high-density urban
areas, and construction financing costs can reach the same order of
magnitude as the construction cost in large projects such as the
construction of nuclear power plants.
设计者和施工管理者应当非常明确的重要一点是，施工建设费用是成本中最主要的一项费用，但是其他费用也不可忽视。例如，在高密度建筑的市区建设一个项目，取得土地的费用是一项主要的成本，而对核电站等这样的大型项目建设，融资成本可能与项目的建造成本基本持平。
From the owner’s perspective, it is equally important to
estimate the corresponding operation and maintenance cost of each
alternative for a proposed facility in order to analyze the life
cycle costs. The large expenditures needed for facility
maintenance, especially for publicly owned infrastructure, are
reminders of the neglect in the past to consider fully the
implications of operation and maintenance cost in the design
站在业主方的角度看，为了分析项目全寿命周期的成本，对每个建设方案的运行和维护成本进行估计是同样重要的。有些项目，尤其是公共项目的物业保养成本巨大，这时刻都在提醒我们，不该像过去那样在项目的设计阶段忽视项目建成后的运行和保养。
In most construction budgets, there is an allowance for
contingencies or unexpected costs occurring during construction.
This contingency amount may be included within each cost item or be
included in a single category of construction contingency. The
amount of contingency is based on historical experience and the
expected difficulty of a particular construction project. For
example, one construction firm makes estimates of the expected cost
in five different areas:
在很多项目的预算中，总有一部分不可预见的费用准备用于施工中的意外情况，这些不可预见费用有可能包含在每一项费用中，也可能作为一项总的不可预见费用。不可预见费用的多少可根据历史经验和特定项目的建设难度来估计。例如，某一建筑公司对不可预见费用的估算包括5
个不同方面。
􀁺 Design development changes.
􀁺 设计变更。
􀁺 Schedule adjustments.
􀁺 进度调整。
􀁺 General administration changes (such as wage
􀁺 总体管理方面的变化(例如，工资水平的变化)。
􀁺 Differing site conditions for those expected.
􀁺 预测的现场条件的不同。
􀁺 Third party requirements imposed during
construction, such as new permits.
􀁺 建设过程中第三方要求所产生的费用，如新的许可要求。
Contingent amounts not spent for construction can
be released near the end of construction to the owner or to add
additional project elements.
没有用掉的不可预见费用在工程末期可以退回业主方，或者用于项目新增部分的建设。
Approaches to Cost Estimation
成本估算的方法
Cost estimating is one of the most important steps in project
management. A cost estimate establishes the base line of the
project cost at different stages of development of the project. A
cost estimate at a given stage of project development represents a
prediction provided by the cost engineer or estimator on the basis
of available data. According to the American Association of Cost
Engineers, cost engineering is defined as that area of engineering
practice where engineering judgment and experience are utilized in
the application of scientific principles and techniques to the
problem of cost estimation, cost control and profitability.
Virtually all cost estimation is performed according to one or some
combination of the following basic approaches.
成本估算是项目管理中最重要的环节之一。它在项目建设的不同阶段为项目的成本建立了一条基准线。在项目开发过程中的某一特定阶段的成本估算就是造价工程师在现有数据基础上对未来成本的预测。根据美国造价工程师协会的定义，工程估价是运用科学理论和技术，根据工程师的判断和经验，解决成本估算、成本控制和盈利能力等问题的活动。实际上，所有的估价活动都是基于以下这些基本方法中的一种或几种方法的组合。
(1) Production function. In microeconomics, the relationship
between the output of a process and the necessary resources is
referred to as the production function. In construction, the
production function may be expressed by the relationship between
the volume of construction and a factor of production such as labor
or capital. A production function relates the amount or volume of
output to the various inputs of labor, material and equipment. For
example, the amount of output Q may be derived as a function
of various input factors x1, x2,…, xn
by means of mathematical and/or statistical methods. Thus, for a
specified level of output, we may attempt to find a set of values
for the input factors so as to minimize the production cost. The
relationship between the sizes of a building project (expressed in
square feet) to the input labor (expressed in labor hours per
square foot) is an example of a production function for
construction.
产出函数。在微观经济学中把过程的产出和资源的消耗这两者之间的关系叫做产出函数。在建筑工程中，产出函数则可认为是建设项目的规模和生产参数(如人工或资金)之间的关系。产出函数建立了产出的总量或规模与各种投入(比如人力、材料、设备)之间的关系。例如，代表产出的Q
可以用代表各种投入的不同参数x1, x2, …, xn
等通过数学和/或统计方法表达。因此，对某一特定的产出，可以通过对各个投入参数赋予不同的值，从而找到一个最低的生产成本。房屋建筑的大小(用平方英尺表示)和消耗的人力(用小时/平方英尺来表示)之间的关系就是产出函数的一个例子。
(2) Empirical cost inference. Empirical estimation of cost
functions requires statistical techniques which relate the cost of
constructing or operating a facility to a few important
characteristics or attributes of the system. The role of
statistical inference is to estimate the best parameter values or
constants in an assumed cost function. Usually, this is
accomplished by means of regression analysis techniques.
经验成本推论法。利用基于经验的成本函数估算成本需要一些统计技术，这些技术将建造或运营某设施与系统的一些重要特征或属性联系起来。数理统计推理的目的是为了找到最适合的参数值或者常数，用于在假定的成本函数中进行成本估算。在通常情况下，这需要利用回归分析法。
(3) Unit costs for bill of quantities. A unit cost is assigned
to each of the facility components or tasks as represented by the
bill of quantities. The total cost is the summation of the products
of the quantities multiplied by the corresponding unit costs. The
unit cost method is straightforward in principle but quite
laborious in application. The initial step is to break down or
disaggregate a process into a number of tasks. Collectively, these
tasks must be completed for the construction of a facility. Once
these tasks are defined and quantities representing these tasks are
assessed, a unit cost is assigned to each and then the total cost
is determined by summing the costs incurred in each task. The level
of detail in decomposing into tasks will vary considerably from one
estimate to another.
用于工程量清单的单位成本法。由工程量清单表达的各项任务或各个组成部分的单位成本能够明确，总成本就是各项产品的数量与其相应单位成本的乘积之和。单位成本法虽然在理论上非常直接，但是难以应用。第一步是将某工作分解成许多项任务，当然每项任务都是为项目建设服务的。一旦这些任务确定，并有了工作量的估算，用单价与每项任务的量相乘就可以得到每项任务的成本，从而得出每项工作的成本。当然，在不同的估算中对每项工作分解的详细程度可能会有很大差别。
(4) Allocation of joint costs. Allocations of cost from existing
accounts may be used to develop a cost function of an operation.
The basic idea in this method is that each expenditure item can be
assigned to particular characteristics of the operation. Ideally,
the allocation of joint costs should be causally related to the
category of basic costs in an allocation process. In many
instances, however, a causal relationship between the allocation
factor and the cost item cannot be identified or may not exist. For
example, in construction projects, the accounts for basic costs may
be classified according to:
混合成本分配法。有时候要从现有的会计账目上去分解，从而确定某项具体操作的成本函数。这种方法的基本思想是，每一项花费都能够对应地分配到操作过程中的某一特定步骤。理想情况是在成本分配过程中，混合成本能够有因果对应关系地被分解，并确定为某种基本成本。但是，在很多情况下，子项目和其分配成本之间难以确定或者根本不存在因果关系。例如，在建设项目中，基本成本可定义为以下5
􀁺 labor.
􀁺 人力。
􀁺 material.
􀁺 材料。
􀁺 construction equipment.
􀁺 建筑设备。
􀁺 construction supervision.
􀁺 建设管理。
􀁺 general office overhead.
􀁺 日常办公开销。
These basic costs may then be allocated
proportionally to various tasks which are subdivisions of a
这几个基本成本有可能会按比例地分配到工程子项的不同任务中去。
Types of Construction Cost Estimates
建造成本估算的类型
Construction cost constitutes only a fraction, though a
substantial fraction, of the total project cost. However, it is the
part of the cost under the control of the construction project
manager. The required levels of accuracy of construction cost
estimates vary at different stages of project development, ranging
from ball park figures in the early stage to fairly reliable
figures for budget control prior to construction. Since design
decisions made at the beginning stage of a project life cycle are
more tentative than those made at a later stage, the cost estimates
made at the earlier stage are expected to be less accurate.
Generally, the accuracy of a cost estimate will reflect the
information available at the time of estimation.
建造成本是整个项目成本中的一部分，虽然很重要，但只是施工项目经理控制下的成本的一部分。在项目建设的不同阶段对估价精确度的要求也不一样，早期只是粗略估计，到施工前的预算就应当是相当可靠了。由于在项目生命周期早期设计方面的决策比后期更加具有不确定性，所以也就不能期望早期阶段的估价会准确。总的来说，估价的准确程度将反映估价时所获取的信息。
Construction cost estimates may be viewed from different
perspectives because of different institutional requirements. In
spite of the many types of cost estimates used at different stages
of a project, cost estimates can best be classified into three
major categories according to their functions. A construction cost
estimate serves one of the three basic functions: design, bid and
control. For establishing the financing of a project, either a
design estimate or a bid estimate is used.
由于不同机构的要求不同，对建造成本估算也存在不同的观点。虽然在项目的不同阶段，建造成本的估算有许多不同的方法，但是根据其功用可分为3
种主要方法。建造成本估算主要服务于以下3 个方面：设计、投标和控制。要对项目进行融资，要么需要设计估价，要么需要投标估价。
􀁺 Design Estimates
􀁺 设计估价
For the owner or its designated design professionals, the types
of cost estimates encountered run parallel with the planning and
design as follows:
对于业主或他指定的设计者而言，在规划和设计过程中要平行进行的估价的种类如下：
(1) Screening estimates (or order of magnitude
estimates).
(1) 匡算(宏观估价)。
(2) Preliminary estimates (or conceptual
estimates).
(2) 初步估算(概念方案阶段估价)。
(3) Detailed estimates (or definitive
estimates).
(3) 详细估算(明确估价)。
(4) Engineer’s estimates based on plans and
specifications.
(4) 工程师基于施工计划和说明的估算。
For each of these different estimates, the amount of design
information available typically increases.
对于以上每一个估价阶段，设计所提供的信息量是逐步增加的。
In the planning and design stages of a project, various design
estimates reflect the progress of the design. At the very early
stage, the screening estimate or order of magnitude estimate is
usually made before the facility is designed, and must therefore
rely on the cost data of similar facilities built in the past. A
preliminary estimate or conceptual estimate is based on the
conceptual design of the facility at the state when the basic
technologies for the design are known.
在项目的规划和设计阶段，不同的设计估算反映了设计进展的不同阶段。在最初阶段，投资匡算或者宏观估价通常是在项目设计之前做出的，因此必须依靠过去类似项目的数据。初步估算或者称为概念方案阶段估价主要基于概念设计方案进行估算，此时只明确了最基本的技术方案。
The detailed estimate or definitive estimate is
made when the scope of work is clearly defined and the detailed
design is in progress so that the essential features of the
facility are identifiable.
The engineer’s estimate is based on the completed plans and
specifications when they are ready for the owner to solicit bids
from construction contractors. In preparing these estimates, the
design professional will include expected amounts for contractors’
overhead and profits.
详细估算或者称为明确估价是在工程范围基本明确、详细设计正在进行、项目的基本特征已经确定时做出的。工程师估算要以明确的施工计划和施工说明为基础，并且业主也可以据此发包选择施工承包商。在做这些估算时，设计人员应将承包商的日程管理费和利润考虑进去。
The costs associated with a facility may be decomposed into a
hierarchy of levels that are appropriate for the purpose of cost
estimation. The level of detail in decomposing the facility into
tasks depends on the type of cost estimate to be prepared. For
conceptual estimates, for example, the level of detail in defining
t for detailed estimates, the level of detail
can be quite fine.
为了进行成本估算，可以把一项设施的有关成本分解成几个适当的层次。层次划分的详细程度取决于成本估算的种类，例如，对于概念设计方案阶段的估价，层次的划分就比较粗，而对于详细设计阶段的估价，层次的划分就应该很细。
As an example, consider the cost estimates for a proposed bridge
across a river. A screening estimate is made for each of the
potential alternatives, such as a tied arch bridge or a cantilever
truss bridge. As the bridge type is selected, e.g. the technology
is chosen to be a tied arch bridge instead of
a preliminary estimate is made on the basis of the layout of the
selected bridge form on the basis of the preliminary or conceptual
例如，要对某条河上的拟建桥梁进行造价估算，投资匡算是对每个潜在的方案进行估算，如是采用拱桥方案还是悬臂桁架桥方案。当桥的类型确定后，比如选定拱形桥而不是其他形式的桥，这时就要基于拱形桥的平面布置，在初步或概念设计的基础上做初步估算。
When the detailed design has progressed to a point when the
essential details are known, a detailed estimate is made on the
basis of the well defined scope of the project. When the detailed
plans and specifications are completed, an engineer’s estimate can
be made on the basis of items and quantities of work.
当详细设计进行到一定阶段，最根本的详细设计已经完成时，就要基于项目的明确范围进行详细估算。当完成了详细施工计划和施工指导说明后，就可以根据各项工作和其工程量进行工程师估算了。
􀁺 Bid Estimates
􀁺 投标估价
For the contractor, a bid estimate submitted to the owner either
for competitive bidding or negotiation consists of direct
construction cost including field supervision, plus a markup to
cover general overhead and profits. The direct cost of construction
for bid estimates is usually derived from a combination of the
following approaches.
对于承包商来说，提交给业主的投标估价的目的是为竞争的需要或者是与业主谈判的需要，投标估价中包括直接施工成本(包括现场监督以及在此基础上增加一笔总体管理费)和利润。用于投标估价中的直接施工成本常用以下几种方法组合计算：
(1) Subcontractor quotations.
(1) 根据分包商的报价。
(2) Quantity takeoffs.
(2) 估计的工程量。
(3) Construction procedures.
(3) 施工方案。
The contractor’s bid estimates often reflect the desire of the
contractor to secure the job as well as the estimating tools at its
disposal. Some contractors have well established cost estimating
procedures while others do not. Since only the lowest bidder will
be the winner of the contract in most bidding contests, any effort
devoted to cost estimating is a loss to the contractor who is not a
successful bidder. Consequently, the contractor may put in the
least amount of possible effort for making a cost estimate if it
believes that its chance of success is not high.
承包商的投标估价常常反映了承包商对完成投标工程的期望值，也反映了其所采用的估价工具。有些承包商拥有良好的估价程序，而有些则没有。由于在大多数工程招标中一般都是最低价中标，所以对于未中标者来说，在投标估价过程中的任何投入都是浪费。因此，如果一个承包商认为自己胜出的机会不是很大，他就会花费尽可能少的精力来进行成本估价。
If a general contractor intends to use subcontractors in the
construction of a facility, it may solicit price quotations for
various tasks to be subcontracted to specialty subcontractors.
Thus, the general subcontractor will shift the burden of cost
estimating to subcontractors. If all or part of the construction is
to be undertaken by the general contractor, a bid estimate may be
prepared on the basis of the quantity takeoffs from the plans
provided by the owner or on the basis of the construction
procedures devised by the contractor for implementing the
如果一个总承包商在设施的建设过程中希望将工程进行分包，他有可能要求各个专业分包商提交分包报价单，所以总承包商将把成本估算的任务转移到分包商头上。如果所有的工程或部分工程由总承包商来施工，投标估计就要根据业主提出的计划和工程量或由承包商提供的施工组织计划来进行编制。
For example, the cost of a footing of a certain type and size
may be found in commercial publications on cost data which can be
used to facilitate cost estimates from quantity takeoffs. However,
the contractor may want to assess the actual cost of construction
by considering the actual construction procedures to be used and
the associated costs if the project is deemed to be different from
typical designs. Hence, items such as labor, material and equipment
needed to perform various tasks may be used as parameters for the
estimates.例如，某类房屋某种基础的成本可以从某些商业出版物中找到其单价，再根据工程量就可以算出成本。但是，项目的实际情况可能导致实际施工程序与一般设计要求不同，在这种情况下承包商就要想办法估算其真实的成本和相关的费用。因此，为完成不同任务所需要的劳动力、材料和设备等就应该作为成本估算的参数。
􀁺 Control Estimates
􀁺 控制估价
For monitoring the project during construction, a control
estimate is derived from available information to establish:
为在施工过程中进行管理和控制，需要基于以下信息编制一个控制性的估价：
(1) Budget estimate for financing.
(1) 财务预算。
(2) Budgeted cost after contracting but prior to
construction.
(2) 签订合同后在开工前的预算。
(3) Estimated cost to completion during the
progress of construction.
(3) 在施工过程中所做的对完工前的成本估算。
Both the owner and the contractor must adopt some base line for
cost control during the construction. For the owner, a budget
estimate must be adopted early enough for planning long term
financing of the facility. Consequently, the detailed estimate is
often used as the budget estimate since it is sufficient definitive
to reflect the project scope and is available long before the
engineer’s estimate.
在施工过程中，业主和承包商都会有一个成本的基准来控制实际成本。对业主来说，必须尽早明确预算(budget
estimate)用于项目的长期财务规划。因而，在工程师估算完成前的相当长时间里，只能用详细估算来作为控制预算，因为详细估算也能充分明确地反映项目的范围。
As the work progresses, the budgeted cost must be revised
periodically to reflect the estimated cost to completion. A revised
estimated cost is necessary either because of change orders
initiated by the owner or due to unexpected cost overruns or
在工程进行的过程中，必须对成本估算进行定期更新，以反映完工前的预测成本。由于在施工中业主可能提出变更要求，或者有不可预见的突破成本或节约成本的情况发生，对成本估算进行及时更新是很必要的。
For the contractor, the bid estimate is usually
regarded as the budget estimate, which will be used for control
purposes as well as for planning construction financing. The
budgeted cost should also be updated periodically to reflect the
estimated cost to completion as well as to insure adequate cash
flows for the completion of the project.
对承包商来说，经常用投标估价作为预算，既可以进行成本控制，也可以进行施工期间的财务规划。该预算成本也要定期更新，以反映完工前的预测成本，并确保项目完工前的现金投入。
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