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General Conditions

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General Conditions

Chapter #7 – General Conditions (MEP Estimating Spreadsheet)

We consider other cost to include general and special condition items, and indirect expenses, those items which are indirectly related to the construction of the project, but which are still required. We will cover the most common of these and how to figure them.

We like to have a separate form with many of the general and special conditions normally found on HVAC projects shown with their cost per unit already on the estimating sheet for quick reference. This will help you remember the most common items and the value that you use for them in each estimate.

General Conditions  – Management

Below is the top portion of the General Conditions tab of the MEP Academy estimating spreadsheet. Your company may use something different but the ideas and concepts of these cost are similar. It doesn’t matter where you locate these cost in your spreadsheet, so long as you have covered their cost if required.

We will cover the most commonly used general conditions for a new construction project.

General Conditions Management
General Conditions Management (MEP Academy Estimating Spreadsheet)

Project Managers

The project manager will oversee all aspects of the project including the project schedule and depending on the company; the project manager could be responsible for estimating, purchasing equipment and materials, and total oversight of the construction.

Project managers can manage many small projects or one large project. The cost of a project manager can be charged to each job for the time spent on that project. You can determine how much project management time you believe the project your bidding will need. Knowing what a project managers cost is allows you to prorate the expense for the duration of the project. You could also charge for the project manager as a percentage of the total cost of the project, such as 5%.

Project Engineers

Project engineers provide useful assistance to the project manager by doing some of the more mundane task of running a project, like preparing submittals, O&M manuals, chasing down drawing revisions and assisting in the overall running of the project. Project engineers are usually overseen by an experienced senior project manager and are more common on larger projects that require additional support for efficient execution of the project requirements.

Superintendent

The superintendent provides oversight of the labor force and coordinates with the project manager and subcontractors on labor aspects. A in company signatory to a union this would be the role of a union worker. For smaller companies this role might be carried out by the project manager.

Safety Managers

Depending on the size of the project and the requirements you could be required to provide a safety manager. The safety manager would be responsible for making sure that the workers follow the project safety requirements, such as wearing hardhats and googles, the proper use of equipment and tools, along with conducting safety tailgate meetings. The safety manager will be responsible for providing training of the field personnel, filing reports and recording any violations of the safety requirements.

Project Estimators

Depending on how your company is setup, the responsibility for pricing change-orders could be allocated to the project manager and his/her team or sent to the estimator located in the offsite company offices. Projects with a lot of change-orders should have the assistance of the estimating department so as not to stifle the project team. The estimating department is better setup to handle change-orders using their estimating software program.

Project/Administrative Assistants

Depending on the size of the project, additional jobsite office personnel maybe required to process all the correspondences and demands of a construction site that isn’t already covered by the project manager or project engineer.

Construction Office – Non-Reoccurring Cost

Non-reoccurring cost are those that will impact the project as a one-time cost as opposed to a monthly expense

construction office non-reoccurring-cost
construction office non-reoccurring-cost

Job Office Mobilization and Demobilization

This is the cost to have the office trailer brought in and setup, then torn down at the end of the project. This cost is independent of the monthly rental fee for the office trailer. Mobilization and demobilization also includes the cost of moving tools and equipment to the site for the execution of the scope of work, and then for the pickup of that equipment and tools at the end of the project.

Construction Office – Reoccurring Cost

Reoccurring cost are those that will impact the project on a monthly or regular basis, as opposed to a one time expense.

construction office reoccurring cost
Construction Office Reoccurring Cost – MEP Academy Estimating Spreadsheet

Job Office Rentals

Jobsite trailers or offices will be required on larger new construction projects as there is nowhere on site for you to conduct the administrative functions of the project. You will need an area to review drawings, and office space for your jobsite personnel.

Job Office Utilities

This is the cost incurred for the use of electrical power, water and gas. Often the general contractor will provide this at no charge, but it’s important to confirm who is paying for these cost.

Job Site Office Telephone/FAX

It’s possible that the project will require a landline and not just the cell phone of the jobsite personnel. You need to figure how long the project is going to last and the monthly cost for the service and usage fees if required.

Job Site Office Supplies

This might include paper for the copier, FAX machine or plotter, along with coffee, cups, sugar, creamer, water and miscellaneous supplies. Plug some value for the duration of the project based on your companies past experience for these type of office consumables.

Parking

Is there adequate onsite parking, or will you be required to rent offsite parking,? Will you be responsible for paying for onsite parking fees? Some of the Universities require the contractors to buy parking permits for the duration of any parking required by their vehicles.

It’s important to know if parking fees will be required to be paid by your company for any vehicles parked at the project site during the renovation or new construction. Area’s around large metropolitan cities, and at some of the Universities during school sessions are crowded and parking is limited. In certain cases you may be required to pay for your own parking.

Additionally, you may be required to bus workers in to the site if parking is provided remotely. Depending on your labor agreement, you may be responsible for getting field labor back to their cars by the end of the day, instead of at the gate or on the site of the project. This would require that you figure losing part of the work day to transporting your field labor.

Temporary Heating or Cooling

This requirement can often be found in the general requirements of the specifications. Add the cost to provide portable heaters or coolers as required. If the temporary system is large, then you will need to contact one of the equipment rental companies that specialize in providing and hooking up temporary systems.

Storage

You need to determine if there is an area on the project site that is allocated for your company to store materials as they are being staged for installation. Unless the project is being run under some form of Lean Construction where just in-time deliveries are being made on  the day the material will be used then some location on site will be required to store and stage material from. If there isn’t any space within the building to store building materials, then you’ll need to rent a lockable storage bin in order to store tools and materials.

Subsistence and Travel

Jobs that require your workers to work beyond certain boundaries as established by the unions, or for which the project is located out of town, and for those you will be sending will require subsistence.

Subsistence
Subsistence

Subsistence helps to compensate the employee for additional expenses incurred while away from home performing his/her duty as an employee. Depending on the location this could include a cost of living increase, as some cities and areas are more expensive than others. The employee may need to stay in a hotel or rent a temporary apartment for the duration of the project as it the distance would make it impossible to drive to the site and back daily. The renting of a vehicle may be required along with round trip airfare.

If you work for a union company then check the union agreement as to the daily subsistence rate for any employee that is required to travel beyond the allotted free zone. If the union employee uses their own vehicle make sure to check the union agreement for any required reimbursement of mileage driven to and from the project site. Most times the union employee is required to get to the project site at their own cost, unless it exceeds a certain distance from the designated union zone map epic center.

Other Cost

As-built Drawings

The requirement to provide as-built drawings or record drawings of the actual installation, should be stated in the specifications. This is almost certain to be a requirement on most projects, and even if it wasn’t a requirement, it is good business practice to provide the owner with a record of the actual installation. This could be as simple as marking with a red pencil or pen the actual routing of ducts and pipes including any size changes.

Liquidated Damages

You won’t put any cost for this in your estimate as the intent is to complete the project as defined in the specifications to avoid incurring a liquidated damages penalty. This might be found in the section entitled progress schedule, where it states that if the project goes past its scheduled completion date, there will be damages assessed. This is a penalty for delaying the completion  of the project, and is usually stated in so many dollars per day for every day that you pass the scheduled completion date.

Get a copy of the MEP Academy Estimating Spreadsheet here >> MEP Academy Estimating Spreadsheet

Understanding the MEP Estimating Spreadsheet (Free Course)

Sheet Metal Field Labor Productivity

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Sheet Metal Field Labor Productivity

Chapter #4 – Sheet Metal Field Labor Productivity

After your reports have finished running on the estimating computer software program its time to review the field labor. If you don’t have a computer estimating software program then your all your field labor numbers would be generated using Excel or some other spreadsheet totaling software. Hopefully your estimating software has the capability to breakdown the labor reports for easy analyses.

We will want to look at the labor productivity, meaning how many linear feet of ductwork is being installed per man-day (LF/MD) as one of the methods of labor analysis, or linear feet per hour (LF/HR) if you want to look at it in a micro sense. A man-day is equivalent to an 8-hour day.

Another method of labor analysis is hours/piece (Hrs/Pc) and pounds/hour (Lbs/Hr). When we took the sheet metal off we separated our takeoff into different zones and systems. At this point we would analyze each zone and system separately.

There is no better way to review the productivity of your project, except to go through it line by line as grouped per your System and Zone descriptions. This will help those in the estimating review to build the job in their head, giving everyone involved a good sense of the project. If you apply a factor overall to everything, no one will fully grasp the project as deeply as a thorough review would allow. Some companies do just that—they apply one factor to all the labor based on the type of project.

We will first cover some of the factors that affect productivity. This is often one of the most difficult undertakings of an estimator, the analysis and adjustment of labor for non-typical conditions. If using a computer estimating program with SMACNA labor units, then you would be adjusting from a 1.0 of SMACNA labor.

Measuring Labor Productivity

This is one of the main duties of the sheet metal estimator, as it has the greatest impact on cost. Labor proposes the highest risk to the contractor, as it is one of the greatest variables. The cost for other aspects of the bid, such as material, equipment and subcontracts shouldn’t vary much from their original bid time cost, unless an error was made.

But labor will vary from your assumptions at bid time about how productive the field labor would be able to install the required equipment and material. So it is labor that really needs to be understood in order to provide accurate estimate that will return a reasonable profit for the owners.

SMACNA Labor Benchmark

There are various organizations that publish labor productivity values for the HVAC Sheet Metal industry including SMACNA, the Sheet Metal and Air Conditioning National Association. There are various factors affecting the productivity of labor from some baseline, or benchmark standard. Each project presents various challenges based on differing site conditions. Labor needs to be adjusted from the standard benchmark labor units to match the specifics of the project under consideration.

Most often labor is the riskiest portion of the estimate because of the assumptions made on the productivity that the project is assumed to be able to redeem. SMACNA provides three progressive categories of labor risk, “Normal”, “Difficult”, and “Very Difficult”. As the conditions worsen, the corresponding labor cost will increase. If you are bidding a retrofit project, one in where you are working in an existing building, then SMACNA considers all remodels to be categorized as either “Difficult” or “Very Difficult”.

SMACNA Labor Tables (Database)

If you are using the SMACNA Reference Manual for Labor Units for your field labor productivity then you will apply a factor to align the SMACNA labor with your field labor feedback (Historical Data), if your company maintains such information. SMACNA labor tables were original assembled from a survey of over 300 member firms from the United States and Canada.

The labor units contain 138 tables for the fabrication and installation unit labor values for the installation of ductwork, fittings, hangers, equipment and accessories. Labor units are available in pounds per hour, or hours per piece, in addition to labor for equipment based on the size of the HVAC equipment.

The SMACNA labor units exclude engineering, supervision, field layout (Detailing) or non-standard construction.

You can use the SMACNA labor units that are embedded in your estimating software if you have one, or you could purchase the SMACNA labor units Excel version, that allows you to adjust values using their spreadsheet. The electronic Excel spreadsheet allows you to rate your project in 30 different difficulty categories in an effort to provide you with the difficulty factor of your project compared to a standard project. There are three project difficulty ratings based on the information you enter for your project, indicated as “normal”, “difficult”, or “very difficult.”

Labor Feedback

The best way to determine how much labor is required for a particular task of work, is to review historical data, that is what it took your companies field crew in hours to perform similar work that has already been completed.

If you are fortunate enough to work for a company that tracks their labor, then you will have a labor database to review when assembling an estimate. The database accumulated from labor feedback will give you a reference for how long it takes to install various materials and equipment, depending on the sophistication and accurate tracking and reporting of the labor spent.

Historical data should be used as a guide for your current project, but not without serious consideration for the differences in the respective projects. Just as SMACNA rates the different categories of labor according to their difficulty, you must know under what conditions your historical database reference project labor was installed under. Understanding what effects labor is the first place to begin before any adjustments up or down from a benchmark labor database is performed.

Industry Labor Database vs Historical Data

There are two main ways to bid labor on a project. The first is to use an industry labor database, and the other is to use some form of historical labor feedback from completed projects. The third way is to use a hybrid of the two. Do your takeoff using the industry standard database, such as SMACNA labor units, and then adjust the productivity according to your historical labor.

The most accurate labor productivity is going to be based on the feedback you received from the field on jobs completed that are similar to the one you are currently proposing, making adjustment for any differences. Let’s look at a few ways to record and adjust labor in the field.

Sheet Metal Labor Productivity Units

There are several methods for analyzing labor productivity for any project. You need to find one that you are comfortable with and that matches the specifics of your company. We will cover four methods of measuring labor productivity.

Duct hung in Wood Structure
Duct hung in Wood Structure

Labor can be measured in LF/MD (linear feet per man day), which means that so many feet of duct can be installed in an 8 hour period, the same unit can be defined as LF/HR (linear feet per hour), which means how many feet can be installed in one hour.

Some contractors like to look at LBS/HR, which means how many pounds of sheet metal that can be installed in an hour. And then there is the HRS/PC (hours per piece), which is defined as how many hours it takes to install a piece of duct or fitting.

MD = 8 hours

  1. LF/MD = Linear feet per man day
  2. LF/HR = Linear feet per hour
  3. LBS/HR = Pounds per hour
  4. HRS/PC = Hours per piece

Linear Feet Per Hour (LF/HR) & Linear Feet Per Man Day (LF/MD)

Ft/MD (Feet per Man Day) is used as a measurement of the labor productivity for a certain ductwork system. If your labor feedback from previous projects indicates that you can install rectangular main ducts at 25 LF/MD (linear feet per man day), then you would apply this productivity factor to the total linear feet of main ductwork you have for the current project if the duct sizes and fitting quantity are similar.

Then you would add any of the labor corrections factors that are applicable for the current project. For example let’s say you have 200 linear feet of main ductwork. You would take the 200 feet and divide it by the historical labor feedback of 25 LF/MD which would equal 8 man days or 64 hours (200 200 LF/ (25LF/MD) = 8 Man Days or 64 Hours.

To this you would adjust for any factors effecting labor. (See course section on “Factors Affecting Field Labor.”) If you receive your ductwork from the fabrication shop KD (knocked down – unassembled), then you will have to add the time it takes to assemble the ductwork on site, which is separate from the time it takes to install the ductwork.

Additionally, if you had 3,000 feet of ductwork and fittings, and your benchmark labor database determined that it would take 800 hours to install this ductwork & fittings, this would equate to 30 LF/MD (30 linear feet per man day)

LF/HR = 3,000 Ft / 800 Hours = 3.75 LF/HR (Linear feet per hour)

To get to linear feet per man day, just multiple by 8 hours in a day.

LF/MD = (3,000 Ft / 800 hours) x 8 Hours/Day = 30 LF/MD

3.75 LF/HR = 30 LF/MD (These two represent the same labor productivity factor)

Pounds per Hour (LBS/HR)

This method is available in the SMACNA labor database as an option for labor analysis. Differing productivity values (Lbs/Hr) are used for different size and gauges of ductwork. As ducts get larger or their gauges get heavier, the duct and fittings increase in weight (pounds).

Example: if you had a 10 feet of 12” x 12” duct at 26 ga, this would equal

STEP-1 Remember that stretch-out is derived by unfolding the duct from a four sided box into a flat piece of metal, so that a 12” x 12” duct unfolded would look like this;

12” + 12” + 12” + 12” = 48” or 4 feet.

STEP-2 Determine how many pounds of sheet metal you have. We have sheet metal ductwork that is 10 feet long by 4 feet wide (stretch-out), which equates to 40 FT2.

10 feet x 4 feet = 40 FT2

STEP-3 Convert the 40 FT2 into pounds by using the conversions value for 26 gauge (0.906 LBS/FT2) galvanized sheet metal, which is.

40 FT2 x 0.906 = 36.24 LBS

STEP-4 Apply your productivity factor (LBS/HR) to the total pounds of duct at this size. Per SMACNA the productivity at this size and gauge is 24.70 LBS/HR. This would calculate out as

36.24 LBS / (24.7 LBS/HR) = 1.46 Hours

The pounds per hour labor productivity factor is the most difficult to visualize. The difficulty comes from the fact that the same five-foot piece of ductwork has different weights at the different gauges, and it’s difficult to tell how much duct weight by looking at hit. It’s easier to count how many pieces have been installed or how many linear feet. What does 300 pounds a day look like, as compared to 25 feet a man-day? It’s easier to visualize the quantity of feet or pieces.

How does the Foreman determine at the end of the day how many pounds the crew has installed? We strongly recommend that you don’t use this method, but choose one of the other labor productivity measuring factors.

Labor Productivity Calculations
Labor Productivity Calculations

Hours per Piece (HRS/PC)

This is the second method available in the SMACNA labor database as an option for field labor analysis. Differing productivity values (HRS/PC) are used for different stretch-out sizes (perimeter). Using the same  10 foot 12” x 12” duct from above, and assuming that we are using 5 foot joint lengths, would mean that we have two (2) 5-foot sections of duct. Using the SMACNA table for low pressure galvanized straight duct with a 4 foot stretch-out and the 26 ga column, we get 0.8611 HRS/PC.

2 pieces x 0.8611 HRS/PC = 1.72 Hours

Using the same 12’ x 12” section of ductwork we can see that depending on which units of labor you use, you derive at different totals. For the LBS/HR unit labor, you get 1.46 hours, while the HRS/PC method gives you 1.72 hours based on the SMACNA database.

Once you decide on which units of labor you will use, then you should stick with it, so that you can develop a sense of familiarity.

Some prefer to use the hours per piece as a means of measuring their labor productivity in the field. This is somewhat similar to the feet per man-day in that if you know the length of each piece of duct

Practice Calculations

Calculate the LF/MD using the following information: (Answers below at end of this course)

Let’s assume your estimating software or manual takeoff has provided you with the following data;

  1. Rectangular Duct = 1,200 feet and 320 hours. (What is the linear feet per man-day?)
  2. Round Duct = 1,800 feet and 240 hours. (What is the linear feet per man-day?)
  3. Adjust the labor productivity to 25 LF/MD for question #1. What are the new hours?
  4. Adjust the labor productivity to 50 LF/MD for question #2. What are the new hours?

Military Project Labor Productivity

This chart is derived from the U.S. Military and shows what they assume it takes to put in rectangular and round sheet metal ducts based on their standard project assumptions. You should establish something similar for your company based on labor feedback from a sample of various project types. This will help you establish your standard benchmark for labor by which all future project labor would be adjusted from, such as SMACNA developed for its membership.

Military Sheet Metal Productivity-Chart
Military Sheet Metal Productivity-Chart

U.S. Military Sheet Metal Labor Productivity Values

Which Labor Unit Method is Best?

We prefer the LF/MD or LF/HR method of labor productivity analysis because it’s visually represented better than the others. For example, if you were to visit a jobsite to review the ductwork that has been installed, and you’re looking at a section of ductwork hanging in the buildings first floor ceiling, could you tell how many pounds of metal it is? This would require you to do some mental gymnastics, or some quick calculation as to what gauge and size the duct was in order to calculate the weight, and then divide by the productivity factor.

Productivity factors using weight in our opinion is not a good labor unit for visually inclined estimators and project managers. There must be a reason why the military uses LF/MD & LF/HR, and that is, it represents an easier way to visualize what has been installed, and for setting a benchmark for field productivity performance.

Proper Takeoff Techniques

Labor productivity factors will vary based on job site conditions as discussed above, but with everything being equal, productivity will also differ based on duct size. There is no way for a crew to install a 64” x 36” section of duct at the same productivity as a section of 12” x 12” duct. So, for this reason your adjustment factors need to be broken down as shown in the military labor unit schedule.

Benchmarking Labor Productivity Performance

When the project is under construction and ductwork begins to get installed, the project management team should begin measuring weekly what was installed and the amount of hours expended for the portion of the project related to the Sheetmetal ductwork. This will let them know if they are hitting their estimated productivity goals.

This is done by taking a fresh new set of drawings out to the jobsite for benchmarking the performance that occurs each week. Each week the ductwork on the drawings that has been installed gets colored on the drawings, documenting the progress of the project. Back at the office, the ductwork that was colored in for that week gets taken off to determine how many linear feet of ductwork was installed compared to how many hours were charged for installing the ductwork that week.

If the sheet metal crew had installed 900 feet of ductwork and they used a six person crew for a week, then the actual productivity would be as follows;

6 Crew Members x 40 Hours/Wk = 240 Hours spent

900 Feet / 240 Hrs = 3.75 LF/HR or 30 LF/MD

Correction/Adjustment Factors

The correction factors shown below are used to adjust a base unit of labor that is considered normal conditions. The correction factors then would adjust this normal condition base unit for any conditions out of the norm. If you review MCA and SMACNA labor units their method is similarly based on a standard unit of measure for which unusual conditions are adjusted. Labor productivity will vary by building type and projects, and may require more or less than the benchmark database labor.

These adjustment factors are just suggestion, and are not hard percentages that you should rely on. All labor adjustments should be something that is derived from experience and historical data that your company tracks. This applies to all the adjustment factors shown in this course.

Height of Installed Ductwork: Anytime your ductwork is hung above 10 to 13 feet you will need to adjust for the increased height. If the field labor can’t work off ladders then you will need some type of scaffold or scissor lift. Add 2% to 10% for ducts hung 11’ to 15’: add 10% to 20% for ducts hung from 16’ to 20’, and so on:

Labor Correction Factor for Ductwork Height
Labor Correction Factor for Ductwork Height

Quantity of Floors: As mentioned above the quantity of floors will have an impact on your labor when the quantity of floors exceeds three. This is the additional time it takes to reach higher and higher floors in the building.

Labor Correction Factor for Quantity of Floors
Labor Correction Factor for Quantity of Floors

Weather Conditions

We all know what it’s like to work in excessively hot or cold weather. Workers just don’t perform at the same productivity levels as they do under normal weather conditions. You can get more done in a nice controlled environment than if you had to work on a cold concrete floor on the 10 floor of a new high-rise that has no walls installed yet, and the cold wind is blowing through the building.

If the project will be built during extreme weather conditions, than you should adjust for a loss of productivity due to the weather. The question is what would the weather conditions be during the duration of the project?

Extremes of either hot or cold weather will result in a loss of labor productivity. Humans don’t function as well when the temperature of the ambient air is outside their comfort zone. This goes for working in areas such as hot boiler rooms or equipment rooms where the temperature is outside the normal range for human comfort.

Temperature Factor on Labor Productivity
Temperature Factor on Labor Productivity

Field Labor Feedback

If you have been in business for any period of time you have established some historical data on the field time required to install ductwork, equipment and accessories. From this historical data, you can project what kind of productivity you should get for the current, similar job. If the jobs are not similar, then you must adjust the productivity up or down depending on the current projects relative ease or difficulty compared to your historical project.

There is no better measure of productivity than your own historical data, but each job will still be unique and should be carefully scrutinized for those areas where productivity could be affected.

Answers to Practice Calculations

  1. 30 LF/MD (1,200 LF/320 hours) x 8 hrs/day)
  2. 60 LF/MD = (1,800 LF/240 hours) x 8 hrs/day
  3. 384 Hours (1,200 LF/ 25LF/MD) x 8
  4. 288 Hours (1,800 LF/ 50LF/MD) x 8
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Sheet Metal Field Installation Course (Free)

Conditions Affecting Field Labor

MEP Academy Instructor
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Conditions Affecting Field Labor

Chapter #11 – Conditions Affecting Field Labor

There are many factors that affect the cost of installing the sheet metal and HVAC equipment in a building. Here is a list of some of the things to consider when analyzing labor productivity. This list is one of the most important things to think about when deciding on how much labor to include in your project.

Working Height

The working height has a great impact not only on labor productivity, but also on the cost of rental equipment. There is a big difference in labor between hanging duct at 12 feet versus hanging duct in a large convention center with a 30 foot hanging height. The latter will require that you work off of some form of elevated platform, whether by scissor lifts or built up scaffolding, the addition of this extra step will require additional planning and installation time to perform the work.

Hanging Duct
Hanging Duct using a Scissor Lift

The height at where your hangers attach to the structure has an impact on field labor, because the hangers are installed ahead of the ductwork and the upper attachment is at the highest point.

Watch the following video and look for the conditions that affect the labor of these workers which include at least the following:

  • Working Height
  • Safety Requirements
  • Material Lift

The question becomes what is your benchmark standard or normal working height from which adjustments will be made. At what height do you bring in a scissor lift or other elevated working platform?

Job Site Conditions

Job site conditions will affect the productivity of the field crew along these three differing scenarios; New construction, retrofit or remodel, and working in an Occupied space. The question is, what type of construction is it?

Ducts above Ceiling
Ducts above Ceiling

New Construction usually allows for less obstruction to performing your labor because walls ceilings and other construction obstructive building components aren’t installed as of yet. This allows you more room to maneuver around with labor, equipment, tools and materials.

Remodels or retrofit projects are just the opposite because you will need to work through the existing construction. All the walls, ceilings and other trades are already installed and possibly obstructing easy access to the work you will need to perform.

Occupied spaces pose another labor intensive scenario because you will need to work around business hours or people while they conduct their business, and existing furniture in addition to all the considerations for a remodel.

Tight Spaces: Attics, crawl spaces, equipment rooms and tight shafts are but a few of the difficult areas due to restricted movement of field labor. You will need to consider these spaces separately and adjust accordingly.

Working in Existing Facilities

There are a lot of factors that come into play when working in an existing facility. First of all will you be working around existing walls, or will they be tore down before you begin your work? This is an important factor, because if you have to move your ladder from one room to another to install your ductwork, that will greatly reduce your labor productivity.

How congested is the ceiling space where you have to install your ductwork? Do you have to work through the existing ceiling grid? Are you responsible to take down the ceiling tiles and reinstall them when you’re finished with your work? Are you responsible for any damaged ceiling tiles? Your labor productivity will be greatly impacted if you have to work through the existing ceiling grid as this will also limit the length and size of the duct sections you can fit through the grid.

Who is responsible cutting and patching of the walls if you need access to a shaft where the duct tie-in will occur, or for the framing of a fire damper? Who is responsible for coring or saw-cutting of floors or concrete walls for the passage of sheet metal ducts?

As can be seen, there are many factors you have to deal with when contemplating the installation of ductwork in an existing facility. That’s why it’s important to attend any pre-bid conferences or job walks. Remember SMACNA considers remodels or retrofit projects to be categorized as either “Difficult or Very Difficult”.

Working Shift

The time at which a worker has to perform a labor task has been documented to affect their productivity. A crew working the swing shift or graveyard shift will produce at lower productivity rate than their counterparts working during normal business hours. You basically have three windows of 8 hours, starting with normal business hours, followed by the 2nd shift (swing shift), and then the 3rd shift (graveyard shift).

Do you have to work around employees during business hours or while the store remains open? Do you need additional time to protect the furniture, flooring or walls?

The question is, when will the work be performed, and does anything need protecting?

Some union workers are paid for 8 hours for only 7-1/2 hours of work when working swing or graveyard shift. Check your union agreement for this requirement or something similar.

Crew Density

You would normally think the larger the crew size the greater the amount of work that would get done, but actually the opposite can be true. There is a point where too many workers on a project site will reduce your productivity levels due to inefficiencies’ caused by too many workers. SMACNA list three crew densities, “Normal”, “Moderate”, and “Extreme”.

Building Square Feet

The size of the building will cause a loss of productivity as the building square feet becomes larger and larger. It will take a lot longer to walk to the work location or to track down tools or material. How do you keep track of all your workers and their productivity in a building the size of a large mall?

It’s unfortunate but there are some workers that will slack off when supervision is out of sight. This is part of how crew sizes can get too big as to cause a lack of overall productivity as stated above. The question is how many square feet is the work area?

Quantity of Building Floors

This is similar to building square footage, except that you are dealing with multiple floors. The higher the building is, the more floors to deal with and workers to keep track of. Up to three floors maybe considered normal, but as more floors are added, several labor factors come into play that will cost additional hours.

In addition to loss of productivity from the additional floors, you will need to take into consideration the additional time it takes to get to the upper floors, such as waiting on manlifts in new construction or waiting on elevators in existing construction.

This is an increase in hours for the labor to get to the upper floors, and for material handling, that is getting the equipment and materials to those same upper floors. Adding 1% to 3% of labor hours per floor for every floor above the 3rd floor is a good starting point for adjusting for additional floors. The question to ask is how many floors is the building?

Building Site Size

Also, similar to the above is the size of the site. Large square feet buildings with many floors and a large construction site is a triple whammy. How far away must your workers park from the building? How long does it take for them to get from where they park to where they will begin their work? Site that are very large may also necessitate some form of small vehicle, like golf carts or gators to get around from one area to another. The question is, how big is the site, and how far away are the workers from their work area when they arrive on site?

Quantity of Hours in a Work Week

Research has shown that after 40 hours of work in a week your labor productivity begins to drop off, and becomes worse over extended periods of time if no reprieve is given. Some may thrive on additional work, but the average worker will lose the ability to remain focused if kept consistently week after week working more than 40 hours. Worker fatigue sets in, and productivity drops. This will have an effect on labor productivity. The question is, how many hours a week are the workers required to work to complete this project on schedule?

Construction Cleanliness Requirements

Depending on the requirements of the project, there are various levels of cleanliness specified by the engineer or dictated by the type of construction. Does the project require a dust free environment, or is it a remodel in a hospital where you might need to work in containment carts? Is it a cleanroom, where you will be required to gown up to prevent contamination of the product? The question is, what are the cleanliness working requirements?

Security Access

Does the project require that the worker and their tools go through a security protocol before entering or leaving the facility? If the project is in a prison, jail, courthouse, amusement park, defense contractor or similar type facility, then it’s possible the workers will lose part of their 8 hour day getting cleared going in and out of the facility. The question is, do the workers or their tools need to go through security each time they arrive or when leaving?

Repetitive Work

If the project consist of work that is repetitive, where each space is exactly the same layout as the previous one, then there should be some labor savings. It’s like doing the same puzzle over and over again, the brain becomes conditioned as to what is expected next, as opposed to having to do a new puzzle every time. The question is, is the work repetitive?

Availability of Labor

How much skilled labor is available for you to call upon to execute this project if you were successful at winning the bid? There are times that various union halls have been drained of the available workers to be called out for a project. If you are a non-union company, where will you find trained workers to complete this project in accordance with the project schedule?

If you maintain a steady crew of workers, and this project doesn’t conflict with any other project commitments you have, then maybe you can get by with the existing crew, but as you grow and expand, the need for additional workers will arise. The question is, do you have the availability of labor required to complete this project on time according to the construction schedule?

Compression of Project Schedule

This factor impacts the crew size as previously discussed, but also involves additional losses caused by having to complete a project in a faster time frame than normal. A compressed schedule means more trade people and their tools, materials and equipment fighting for limited space, all in an effort to complete the project in an accelerated schedule.

The idea is that anytime you are required to accomplish something beyond a reasonable time, it will impact labor, and possibly quality, requiring additional reworking of previous rushed work. The question is, is there enough time allocated in the schedule to complete the project in a reasonable time?

Condition of Project Documents & Responsiveness of Engineering Team

If the plans and specifications are lacking in information and completeness, then time could be lost waiting around for decisions to be made and RFI’s (request for information) to be answered. The question is, are the documents well done and ready for construction with minimal RFI’s required?

Material Handling

When installing a lot of sheet metal ductwork and air distribution devices, then time must be considered for how you are going to identify what goes where and how you get it to the location where it gets installed. Material handling gets the duct from where it is delivered at the site to the location where it is going to be installed.

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Sheet Metal Duct Sealer and Leakage

MEP Academy Instructor
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Sheet Metal Duct Sealer and Leakage

Chapter #6 – Sheet Metal Duct Sealer and Leakage

Duct Leakage

Duct leakage is a factor of the static pressure in the ductwork that allows for leakage to occur through holes, seams, joints and penetrations. Leakage is a loss of energy, which means a loss of money. This is why it’s so important to seal the ducts and to prevent leakage. Leakage can also occur at equipment and accessories that are installed into the system including dampers, smoke/fire dampers, VAV Boxes and access doors.

SMACNA Duct Seal Classes

Ducts are required to be sealed according to SMACNA Table 5-1 based on the duct pressure class (#1), which is broken down into three categories of pressure. Depending on the pressure class of the duct, there will be a corresponding Seal Class (#2) from C to A.

As the pressure increases in the ductwork the applicable sealing requirements (#3) will apply to various aspects of the ductwork, starting with Transverse Joints Only (Seal Class “C”), then Transverse Joints & Longitudinal Seams (Seal Class “B”) and finally All Transverse Joints, Seams and Wall Penetrations (Seal Class “A”).

Recommended Leakage Class
Recommended Leakage Class

Duct Sealing

There are various sealing requirements.

This video shows how duct sealer is applied with a brush. It appears to be a messy job, but the idea is to make sure that all the joints and seams are air tight so as to avoid duct leakage, including brushing sealer over all screws used in fabrication. Ducts that leak are wasting energy and preventing the conditioned air of doing its job of providing a comfortable environment for the occupants.

Duct Sealing

There are various types of sealer including some that are required to be of low or no VOC (Volatile Organic Compounds) when a building is seeking to get LEED (Leadership in Energy and Environmental Design) certified or when requested by an environmentally conscious owner. The IEQ Credit 4.1: Low Emitting Materials is worth 1 point in the LEED certification program. This LEED credit applies to various sealants and adhesives used on the interior of construction projects in addition to duct sealer, items such as carpet and floor adhesives.

The Adhesives, Sealants and Sealant Primers must comply with South Coast Air Quality Management District (SCAQMD) Rule #1168.

Joint Sealing

Joints are sealed with Butyl Gasket to prevent leaks at the connection points between ducts, fittings and accessories.

Applying Gasketing

Duct Leakage

SMACNA doesn’t recommend pressure testing on duct pressure classes of 3” wg and less, as its not economically feasible. Be sure to check the specifications and your local or state energy code for this requirement. Leakage testing could be shown in the Testing & Balancing or the Ductwork section of the specifications.

Some states, like California require pressure testing on small systems (spaces 5,00 Ft2 or less) when 25% or more of the ducting is located in a non-conditioned space, one not intended to be occupied by people. This applies to both new and renovated projects.

Also some of the utility companies that offer energy saving incentives or rebates require pressure testing to confirm a maximum level of leakage in order to qualify for their program.

Sealing Ductwork
Duct Leakage Test

Duct Leakage Allowed

SMACNA publishes Table A-1 “Leakage as Percentage of Flow in System” that if specified in your local code or the design specifications, shows the percentage of leakage (#5) at various Static Pressures (#1) and Leakage Classes (#2). This is also effected by a calculation (#4) of the Fan CFM divided by the Ducts Surface Area (#3), shown as; CFM/Duct Surface Area. The product of the calculation is available at 2, 2.5, 3, 4 & 5 (#3).

Duct Leakage Percentage Table
Duct Leakage Percentage Table

Note that as the pressure increases (#6) so does the percentage of duct leakage. As an example, if you had a duct rated for 2” static pressure and the specifications called for a leakage class of 16, you would get a rate of 13% leakage, assuming your calculation (#3) for Fan CFM divided by Duct Surface Area equaled 2 or less.

Item (#7) above shows what the Table 5-1 “Recommended Leakage Classes” above would look like on this leakage rate chart. Item #7 shows for rectangular duct (highlighted in blue), while item #8 on the chart above is reflective of round duct (highlighted in green).

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