AACE International - Technical - Parametric Cost Estimating Model for Buildings

AACE International welcomes you to try out this illustrative example of a parametric cost estimating model. Before using the model, see About the Technology and About the Model sections for more information on the capabilities, scope, and limitations of the model methodology. See About the Input / Parameters for specific details concerning the input parameters that you will enter in The Model. The output/results of this model is a total building cost estimate, including architects fee, broken down by building system in accordance with the Construction Specification Institute's Uniformat accounts.

About the Technology
About the Model
About the Input / Parameters
About the Output / Results
The Model
Disclaimer
Credits

This tool is a working example of a parametric cost model. A parametric cost estimating model is made up of one or more algorithms or cost estimating relationships (CERs) that translate technical and/or programmatic data (parameters) about a product or asset into cost results. The algorithms are commonly developed from regression analysis of historical project information, however other analytical methods such as neural networks are sometimes used. The models are very useful for cost and value evaluations early in the project life cycle when not much is known about the project scope. The models are limited in accuracy and usage due to the many assumptions built into the algorithms. Also, the validity of the model is usually limited to certain ranges of parameter input values. Due to these limitations and constraints, it is incumbent upon the user to thoroughly understand the basis of a parametric model.

This illustrative cost model is made up of a set of algorithms -- one for each of the "systems" that make up a building and one for the architects fees to design the building. The building cost accounts shown are the major divisions of the CSI Uniformat which is commonly used for parametric building cost evaluations due to their "systems" orientation.

The model is generally applicable to the typical kinds of buildings found in an industrial or commercial setting in the United States (up to 7 stories, steel or concrete structure). This includes offices, warehouses, industrial buildings, and labs. It does not apply to residential or wood construction. It does not cover buildings over 7 stories or monumental grade buildings with elaborate closures and finishes. It also does not provide for clean room conditions. The estimate does NOT include contingency.

All cost estimates should include a contingency allowance to cover for unidentified but expected cost occurrences within the project scope. Contingency is usually estimated through the application of risk analysis techniques.

The following is the list of model input elements, their use, and range of values.

Case Description
(Optional) labeling of parameter set, especially useful if printing the results for distribution and/or saving the parameters for later use.

Floor Area
In square feet - Enter the total usable square feet of the building floor area measured from wall-to-wall including all stairwells, closets, etc. Include all floors in multi-story buildings, except use 1/2 the measured area for basement levels. No default. (The system has a scaling adjustment to account for economies of scale -- 20,000 SF yields no adjustment.)

Floor Height
In feet - Enter the average number of feet from the floor surface on one story to the floor surface of the next. For single story buildings use the distance from the floor slab to the eave. For multi-story buildings, divide the total building height from base slab to roof eave by the number of floors.

Number of Floors
In whole number - Enter the number of floors or stories including basement levels, Maximum of 7.

Percent of Area as Office
Enter percentage of the Total Floor Area that will be built as office space. 0 to 100%
Note: the sum of the %'s for (office + wet lab + dry lab) must NOT exceed 100%. Space not allocated to office or labs is assumed to be largely open for warehouse or industrial usage.)

Percent of Area as Wet Lab
Enter percentage of the Total Floor Area that will be built as wet lab space. 0 to 100%

Percent of Area as Dry Lab
Enter percentage of the Total Floor Area that will be built as dry lab space. 0 to 100%

Percent of Area Heated
Enter percentage of the Total Floor Area that will be heated space. 0 to 100%.

Percent of Area Cooled
Enter percentage of the Total Floor Area that will be cooled or conditioned space. 0 to 100%

Number of Corners
In whole number - Enter the number of corners the exterior closure has. For instance, a rectangular building has 4, L-shaped has 6, cross has 12, etc. No maximum.

Structural Strength/Duty Factors (Sub-Structure and Super-Structure)
In whole number from 0 to 10 - scalar indicates the relative strength of the Sub-structure (caissons, slab, etc.) and Super-structure (above grade structure). Use the following rough guidelines based on the imposed floor loading in lbs per SF:

0 = 50 (light foot traffic, light roof	6 = 326
1 = 96 (light office, heavy roof)	7 = 364 (heavy mfg, live loads)
2 = 142 (heavy office, lab)	8 = 410
3 = 188 (light mfg, mixed use)	9 = 456
4 = 234	10 = 500 (v. heavy mfg, high live loads)
5 = 280 (mixed mfg., warehouse)

Note: For 1-story buildings use 1 or 2 for the Superstructure if it only supports the roof (slab may be much heavier).

Exterior Closure Finish Quality
In whole number from 1 to 10 - scalar reflects the average quality and duty of the closure construction including walls, windows, and doors. Use the following rough guidelines:

1 = Corrugated metal	6 = Curtain Wall
2 = Wood, Aluminum	7 = Composition or Cavity, brick face
3 = Block, Tilt-up, Sandwich Panel	8 = High Quality Curtain Wall
4 = Precast, Decorative Block	9 = Composition/Cavity, stone face
5 = Composition/Cavity, block face	10 = Expensive Stone

Note: As the number of windows increases it tends to push up quality ratings under 6 and decrease it over 6 (i.e windows tend to cost more than wall under 6).

Interior Construction Finish Quality
In whole number from 1 to 10 - scalar reflects the average quality and duty of the interior construction including partitions, floor coverings, ceilings, etc.. Use the following rough guidelines:

1 = functional, unattractive	6 = moderate duty, attractive
2 = functional, passable	7 = heavy duty, passable
3 = light duty, passable	8 = heavy duty, attractive
4 = light duty, attractive	9 = moderate duty, luxury
5 = moderate duty, passable	10 = heavy duty, luxury

Note: the % office/lab parameters already account for the fact that finished space is present - the answer here refers to how nice those interiors are.

Mechanical Services Quality
In whole number from 1 to 10 - scalar reflects the average quality and duty of the mechanical services including HVAC, fire protection, plumbing, etc. Use the following rough guidelines:

1 = functional, no sprinklers	6 = moderate duty, extra hazard
2 = light duty, no sprinklers	7 = heavy duty, ordinary hazard
3 = light duty, light hazard	8 = heavy duty, extra hazard
4 = moderate duty, light hazard	9 = max duty, ordinary hazard
5 = moderate duty, ordinary hazard	10 = max duty, extra hazard

Note: the % heat/cool parameters already account for the fact that HVAC is present - the answer here refers to how good those services are.

Electrical Services Quality
In whole number from 1 to 10 - scalar reflects the average quality and duty of the electrical services including lighting, convenience power, and HVAC/mech power, etc. Use the following rough guidelines:

1 = low light, functional, EMT	6 = bright light, passable, EMT
2 = low light, passable, EMT	7 = bright light, passable, RGS
3 = moderate light, functional, EMT	8 = bright light, attractive, RGS
4 = moderate light, passable, EMT	9 = max light, passable, RGS
5 = moderate light, attractive, RGS	10 = max light, attractive, hazard

Note: the % office/lab parameters do not account for the quality of lighting - select average area lighting level here.

Escalation Factor
Used to adjust the model relative to the base year and currency, 1995 US$. Default value is 1.00. Range permitted is 1.00 to 2.00.

Location Factor
Used to adjust the model for local conditions impacting costs. A three-value predetermined scale is used. Default is 1.00 (for "US Average").

Local Productivity Factor
Used to adjust the model for local conditions impacting productivity, and therefore costs. Use subject to individual judgment. A four-value predetermined scale is used. Default is 1.10 (for "fair").

The result of this model is an approximate building cost estimate, including architects fee, broken down by building system in accordance with the Construction Specification Institute's Uniformat accounts. The costs include all labor and material as well as an allowance for contractor's overhead and profit.

The results exclude the following significant items:

excludes site improvements (land, landscaping, parking, utilities, etc.)
excludes furnishings and production equipment
excludes contingency allowance

All cost estimates should include a contingency allowance to cover unidentified but expected cost occurrences within the project scope. Contingency is usually estimated through the application of risk analysis techniques.

The model output is presented in a new browser window in two major sections. A tabular "chart of accounts" that is the results of the computations, and a recapitulation of the input parameters. Each execution of the model will result in a new results window, so it is possible to compare different cases on a side-by-side basis. Each window can be managed using the normal window controls of your system (close, minimize, maximize, resize).

This cost model is made available as an illustrative, educational example of the types of tools and technology used in the practice of cost engineering and parametric estimating. To try the cost model click here.