No matter what is accomplished, it starts with a vision in someone's mind of the end result. At the other end of the spectrum is evaluation. In between, the vision and evaluation of the end result are the planning and implementation phases. In the building design and construction profession, it is a four-step process: predesign (vision), design (planning), construction (implementation), and project close-out/occupancy (evaluation).

The first step in getting what you specify is establishing the product selection criteria during the planning phases of a project. The specification of the product is part of the planning phase. Review of proposed substitutions of other products, the submittal review, site visits, and punchlists are all part of the contractors' implementation phase; however, these steps are also the start of the engineer's evaluation phase. Project closeout, occupancy of the facility, and ultimate use by the owner completes the evaluation process. Typically, the first year of occupancy - the warranty period - is the main evaluation period. This is the period during which the owner can generally get things corrected without having to pay additional fees.

Why Is This Happening?

Has it ever happened to you? You spend hours engineering a project design, have it all worked out, considered all the reasonable options that you know of, selected the basis-of-design products, detailed everything on the drawings, written the specifications, and put the job out for bid.

Then it comes in over budget and a cost-cutting exercise (sometimes erroneously called value engineering) gets underway, wherein the contractors make suggestions to the owner as to how to save money on the job. You're the engineer who thinks things through, is diligent in your professional work, yet something didn't turn out the way you planned - what went wrong? Did you have bad data from which to make all the decisions? Was the budget too low? Did prices rise too much from when you did your last estimate with the best data available from professional databases and from actual "budgetary ballpark" estimates given to you by the manufacturers' representatives? Why does the contractor want to propose cost-saving substitutions?

Or, has it ever happened that a contractor simply decides to "redesign" the job another way or arbitrarily starts submitting products that weren't in the original contract document or submitted via the official substitution process?

How should the engineer deal with these situations? Hopefully, after reading this article you will be more confident in knowing what to do in each of the above situations in order to get what you specified for your client.


Every project begins with an idea or a need - a vision. The owner and the A/Es explore this vision during what is called the predesign phase.

Predesign phase. This phase generally includes feasibility studies, market analysis, programming, budgeting, site evaluation, and environmental impact studies, etc. This is the phase wherein the owner determines if the vision is achievable and worth undertaking as an investment. Very little in-depth product selection is done during this phase of the project; however, budgeting that is done at this phase starts to set the tone for the criteria that will be used to select products.


In the construction industry, the planning phase is called the design phase. There are generally three phases to the design phase of a construction process: schematic design (SD), design development (DD), and construction documents (CD). During each phase, the designer (engineer or architect) makes certain decisions regarding the products that will eventually be included in the contract document specifications.

Definitions. Note the distinction that CSI (Construction Specifications Institute) makes between CD and "contract documents." CD is a phase of the design process. The documents produced during this phase are defined as "the written and graphic documents prepared or assembled by the AE for communicating the design of the project and administering the contract for its construction." "Contract documents" is defined as "the legally enforceable requirements that become part of the contract when the agreement is signed" between the owner and the contractor.

Contract documents are a subset of CD. Likewise, contract drawings and contract specifications are subsets of the contract documents. It is necessary to keep the terms straight in order to fully appreciate the proper procedures involved with preparing these various documents.

To help explain this, according to the CSI Manual of Practice, CDs include:

Bidding Requirements:

  • Bid solicitations;
  • Instructions to the bidders;
  • Information available to bidders;
  • Bid forms and supplements; and
  • Addenda.

Contract documents:

  • Contract forms;
  • Conditions of the contract;
  • Contract specifications;
  • Contract drawings;
  • Addenda; and
  • Modifications.

The owner/contractor agreement does not directly include the documentation included in the bidding requirements. These documents are used to communicate information to the bidders about the bidding process. Once that is done, these documents have served their purpose.

Contract specifications are defined by CSI as "the qualitative requirements for products, materials and workmanship upon which the construction contract is based." The word "specify" in its simplest meaning is "to describe or define in detail."

Contract drawings are defined by CSI as "graphic and textual information organized on a two-dimensional surface for the purpose of conveying data about a specific portion of a project." Drawings convey "design intent."

Note that nowhere in these definitions does it say, "build as shown or specified." It does say that these documents are for showing design intent. It is not the intent of the professional architect or engineer to tell a contractor how to specifically build a building.

The question always boils down to which is more legally binding, the drawings or the specifications. The answer is neither. They are both part of the contract documents and carry equal weight, as long as the contract documents don't specifically give one or the other more authority in case of a discrepancy.

SD Phase

During the SD phase, the conceptual design criteria is established for the project. The design criteria consist of written preliminary descriptions of the products and performance criteria that these products will be required to meet. During this phase of the project, the focus is on the aesthetics, form, function, and budgets for the project, not on product selection. During the SD phase, the decision of HVAC system type is generally made, e.g., constant vs. VAV systems, pneumatic/electric vs. DDC systems and components, centrifugal vs. vaneaxial fans, gas vs. electric heating, and central plant chillers vs. rooftop DX units, etc.

DD Phase

During the DD phase, the focus is on the technical aspects of the project and product selection. The "outline specifications" are written to document and describe the products and other design decisions that have been made to this point in the design process. The decisions at this point are made to select between the options that were identified in the SD phase both at the system and product levels.

CD Phase

During the CD phase, the final basis-of-design systems and products are selected that will be included in the project specifications to obtain bid or negotiated contract prices. The product sizing, detailing, options, and features are all incorporated into the contract drawings and specifications.

Product Selection

There are many aspects, characteristics, features, and attributes that can be considered when products are evaluated for their potential use on a project. Whether they are cognizant decisions or not, the criteria by which a product is specified and ultimately evaluated and provided is decided upon and documented in the contract documents. Ideally, all products that are installed in a building are evaluated with respect to how they integrate into the whole building and how their function affects the rest of the building.

Required Function(s)

Getting what you specify depends on whether or not a product can meet the desired required function(s) and be obtained at a cost within the budget allowed for that portion of the project. If the required function is clearly defined and a realistic budget is presented, then getting what you specify should be no problem. If, however, a product can't meet both of these criteria, then one of the criteria must change until a product can be found to meet the criteria.

It is important to understand what is meant by required function. The required function is not only the performance characteristics of the product once it is installed in the building. The required function also takes into consideration the requirements of the project including space efficiency, first cost, energy cost, etc. All of these attributes (parameters, criteria) must be clearly prioritized and communicated to the owner/client during the design phase of the project in order to ensure that the design meets all of the project goals.

If, for instance, at the design phase, the owner agrees that an energy-efficient HVAC system with multiple levels of comfort control for the building occupants is a high priority, then the design team will use this required function parameter to select the HVAC system to complete the contract documents. If the owner determines after the bids are in that he prefers the contractor's proposal to save a given amount of money by installing a single-zone rooftop unit with reheat coils, then the owner is not sticking with the "required function" as determined at the design phase of the project.

At this point, the owner has deviated from a previously agreed upon parameter and made "first cost" a higher priority than comfort or ease of maintenance that would have been possible with the original system design. It is appropriate at this point for the original engineer of record, who applied her professional seal to the set of bid/permit documents, to withdraw this seal from the contract documents. It is also appropriate for the engineer of record to negotiate for additional fees to evaluate the contractor's proposed cost-cutting measures based on the new set of design criteria if she decides to stay as the engineer of record.

Selection Criteria

Both CSI and ASHRAE have guidelines for system and product selections. Each of these procedures starts with a list of assessments or attributes that must be considered when selecting a system or product with the system. Not all of the assessments and attributes indicated on these lists will necessarily apply to all projects. Neither is either list necessarily exhaustive of all considerations that could be taken into account. The use of the two lists in conjunction with each other gives a good starting point for most any type of project and product selection decision-making process.

System Selection Criteria

The ASHRAE 2000 HVAC Systems and Equipment Handbook outlines a system/product selection procedure as follows:

  • Performance requirements.
  • Capacity requirements.
  • Space requirement considerations (architectural constraints).
  • Floor space;
  • Plenum space;
  • Furniture placement;
  • Maintenance accessibility; and
  • Roofing requirements.
  • First cost.
  • System cost;
  • Cost to add zones;
  • Ability to increase capacity;
  • Contribution to life safety needs; and
  • Air quality control.
  • Operating cost.
  • Energy cost;
  • Gas; and
  • Electricity.
  • Maintenance cost.
  • Economy cycle (free cooling); and
  • Heat recovery.
  • Reliability.
  • Flexibility.
  • Maintainability.
  • Facility owner's goals.
  • Supporting a process;
  • Promoting an aseptic environment;
  • Increasing sales;
  • Increasing net rental income; and
  • Increasing the salability of a property.

Product Selection Criteria

The CSI Manual of Practice has a different list than ASHRAE; however, parallels can be seen. According to CSI, identifying the project requirements and product functional requirements within the project is the first step in the product selection process. The CSI list is as follows:

  • Safety and protection.
  • Fire safety;
  • Life safety (other than fire);
  • Property protection/security; and
  • Accessibility considerations.
  • Functional characteristics.
  • Strength;
  • Durability;
  • Stain resistance;
  • Transmission characteristics;
  • Waste products and discharge;
  • Operational characteristics;
  • Aesthetic properties;
  • Acoustic properties;
  • Illumination;
  • Ventilation;
  • Measurable characteristics; and •Material properties.
  • Practical characteristics.
  • Interface characteristics;
  • Service;
  • Replaceability; and
  • Personnel needs.
  • Cost.
  • Material cost;
  • Installation cost;
  • Initial cost - material and installation; and
  • Life-cycle cost/value engineering.
  • Legal requirements.
  • Case studies;
  • Other legal studies;
  • Failures;
  • Errors and omissions;
  • Problems; and
  • Legislation.
  • Codes, standards, and references.
  • Codes and regulations;
  • Standards;
  • Testing, inspection;
  • Indexes;
  • Directories;
  • Symposia, technical meetings; and
  • Research and development.

Evaluation During Design

Identifying and evaluating systems and products must be done on the basis of satisfying the needs assessment of the functional requirements if a logical approach and result is desired. Once a needs assessment has been conducted, then and only then should the product evaluation start. The product evaluation process suggested by CSI has five major aspects:

  • Product characteristics: "... construction products will have different characteristics, making no two identical in every respect. The A/E should determine what degree of variance in product characteristics can be allowed and still be acceptable."
  • Manufacturer: "There will be many instances when it will be preferable to name the acceptable manufacturers in the project specifications. As an option, certain manufacturer's qualifications can be required. Identifying those qualifications is as important as the selection of the product itself."
  • Installation requirements: "The manufacturer's directions for installation/application should be examined to determine if they are complete and specific."
  • Initial and operational costs: "Installed cost is a key concern. A product may have a low material cost, but require expensive, labor-intensive installation. For many projects, life-cycle cost may be a more appropriate measure of value."
  • Maintenance requirements: "Inexpensive products may become the most expensive when their maintenance costs over the life of the project are included."

In addition to these factors, it is also important to take into consideration the manufacturers' representative company that is supplying the product. The organization and individual sales people should be trustworthy and have an ethical standard that ensures that what is being provided is indeed what has been documented in the contract documents. After the sale, a reliable manufacturers' representative agency will attend to service and warranty issues. In addition, a good manufacturers' representative agency will conduct proactive marketing and educational service to the design team to help them understand the application of the products and establish realistic "required functions."


Vision, planning, implementation, and evaluation. In this first of a three-part article, the concepts of vision and planning were discussed as related to product selection procedures. It is essential to visualize the end result of any HVAC design so that the products selected meet the design functional requirements.

In the second part of "Getting What You Specify," you will find some helpful information about intangible aspects of the design process like communication/documentation, knowing and distinguishing between your client's project needs vs. wants vs. wishes. That article will also address proper specification-writing techniques, how to handle substitutions, and how to deal with submittals. ES