Last month's column covered some of the basics of the labor unit, including the need to factor it. Factoring is customizing the labor unit to fit the assumptions made while preparing the estimate. A variety of factors can affect adjustments to labor hours. Geographic factors account for weather variations and the seasons. Others can be better categorized and are included in the NECA Manual of Labor Units. Other publications produced by NECA and sub-contractor groups provide additional information. Another source is the Electrical Contracting Foundation, which sponsors research on various electrical contracting topics. One such report is entitled, "Accelerated Construction Schedules Cause Productivity and Profit to Suffer." The study covers the practice of excess staffing of projects. Poor project management can lead to blame of the estimator for not having originated a reasonable expectation of a schedule. Computer estimating system users should be able to transmit their labor hours to a scheduling program. The prime basis for adjusting labor units would be any circumstance that varies considerably from the scope of the conditions assumed when a labor unit is listed. The scope of the introduction to the NECA Manual of Labor Units is a good starting place, as well as those ahead of each major section. If the novice estimator will note such variances, an experienced estimator can assist or make the necessary adjustments. Some of the items mentioned may be mentioned in the specifications. For example, the "beneficial occupancy" clause, meaning that the future occupants of the building may be able to move in to use the facilities before their completion can be a major consideration, depending on the amount of work that will have to be done under such circumstances. One of the prime reasons for factoring labor units is the type of project. A grouping of standard, difficult, and very difficult project types are also listed in the NECA Manual of Labor Units. Further separation within the listed categories is optional and appropriate when a contractor tends to specialize in a particular type of work. Thirteen additional conditions are in the Manual of Labor Units. These conditions are not universally applicable, but they may lead to factoring labor units. Several NECA pamphlets provide in-depth information on factors that affect labor. A common question is how much of an adjustment factor is advisable to apply to a high-rise building. "The Effects of Tall Buildings on Productivity" can be a valuable source. For estimating jobs where temperatures or conditions can be production reducers, the pamphlet, "The Effect of Temperature on Productivity" can help to assess the lost labor due to high humidity or other factors. Good project management includes having "just the right" number of workers on the job. If a large workforce is required for part of a project, people may be pulled from other projects, lowering production there. How much labor to allow for such a circumstance? A couple of booklets that deal with peak workforces and the rate of labor consumption help estimators answer that. The Electrical Contracting Foundation study quotes a Mobil Oil figure that suggests that a project density of people working in the same area should not exceed 200 square feet per person. The study further suggests that, when the density drops to 150 square feet, a labor adder of 50 percent must be applied. In addition to the Electrical Contracting Foundation, the Business Roundtable in New York has conducted studies for major owners that can be of value. Good industrial engineering textbooks describe further considerations. Labor factors vary according to the shapes of a building. A rectangular portion of a building is likely to carry one labor factor, while a circular building would warrant another. Another major consideration of the scope of the labor factor is who is bidding for the projects. Project management varies between firms, which affects the electrical subcontractor. This is why many estimators scale their estimates to various contractors on the same project. Since factoring is subjective, a firm basis of information is a salient requirement. The best database is the record of the contractor's previously completed projects: the more information the better. Manually estimating and following up during a project makes such detailed information somewhat cumbersome. Many experienced estimators who have internalized much of this information may arbitrarily apply factors, which can lead to disaster. Computerized estimating and data collection is a more reliable method. Some estimating programs allow a project to be separated easily into multiple segments to make provisions for varying labor units. Such systems should also allow separation of the many factors that go beyond the normal scope of labor units. DAVID is a professor of electrical technology at Long Beach City College, Calif., a consultant, and an expert witness. He can be reached at (562) 597-1877 or by e-mail at email@example.com.