Challenges and Methods of Estimating a Conceptual HVAC Design:
In any conceptual HVAC design, estimators are faced with the challenge of trying to capture all of the pieces that complete a system. The difficulty in this can be that they are faced that there is limited information for the estimator to fully complete an estimate.
The only way to accurately complete an estimate is for an estimator to use past experience.
Using previous completed jobs as a template can help an estimator determine how to approach the estimate. Another advantage of having this experience is knowing the order in which the HVAC components should be taken off, since one item will affect how another is quantified. Past jobs will help an estimator determine how much duct work is needed based on square meter calculation, or how much piping will be needed for each piece of equipment.
The contents of this publication will discuss the major components of a HVAC system and the difficulties and methods in determining quantity with limited specifications and information.
There are three major cost components that make up a mechanical system. These include equipment, piping, and duct work. These three items will be discussed in detail on how their design and layout can impact cost and how to determine what is actually needed to complete the system with little information. Only the most common HVAC designs will be identified here.
Estimating a conceptual HVAC system can prove to be difficult, especially if drawings are not yet designed. Many factors have to be considered when trying to visualize how a HVAC system will be built.
In many cases when trying to estimate a project that has not yet been completed, an estimator essentially has to become an engineer. Use of experience and knowledge is needed to complete a design that is incomplete. Explore to HVAC systems as an estimator gives you chance to see different engineered systems and how they are used. Experience with working with these many different systems will help accurately put together cost estimates with little information. This experience and knowledge proves to be useful, especially if architects are uncertain that a specific design will work and be with‐in a project budget.
HVAC costs can often be one of the most expensive internal components of a project. Being able to fully understand and estimate its value, can make an estimator very beneficial to a project that is still in the early stages of design.
HVAC EQUIPMENT
The most complex and expensive component of a mechanical system is the equipment. In any commercial project the goal of the mechanical equipment system is to heat and cool the building the most efficient and cost effective way. The first thing an estimator must establish is what type of mechanical system is being used. Most of the time big components of equipment will be listed and sized in the narrative. The challenge to the estimator is that not all of the smaller equipment will be shown to complete the system.
Two things to always consider when doing an HVAC estimate is: what type of equipment will heat and cool a building and, what type of equipment will supply and exhaust the air. These two components are different in nature, but act as one to complete a system. In the following paragraphs, here it is explained how using information obtained from the narrative or architect will help an estimator.
This information will include size of the building, number of rooms, function of the building, and what type of major HVAC equipment will be used. It will also help an estimator identify additional equipment that will be needed and the quantities. This will insure that the estimator has effectively put together a
complete system and all of the components are captured.
MAIN HEATING EQUIPMENT
The method used to heat and cool a building is to supply hot and cold water to the air supply equipment coils. Heat for the HVAC system can be achieved two different ways. The most cost effective system is to use steam to heat the water. This is assuming steam utilized comes from an existing steam plant which is commonly found on large university sites or large medical facilities. Steam is used to heat water through the use of a heat ex-changer and estimators must be aware that a pressure reducing station will be required if this system is used. Figure 1 (steam heat ex-changer) is an example of how a steam heat ex-changer works.
Figure 1 Steam Heat Exchanger
The second most common way to heat water is through the use of boilers. Boilers can be heated by the use of electricity, coal, steam, or gas. Depending on the size of the building, the most common method in commercial construction is the use of a gas boiler. Typically, any building over 1,859 square meters uses gas because it provides benefits such as cost and heating efficiency.
Figure 2 (gas fired boiler) shows how water enters a boiler and is heated.
Figure 2 Gas Fired Boiler
MAIN COOLING EQUIPMENT
Cooling a building works in the same manner as heating, except the equipment will cool the water instead of heat it. The most typical way to cool water is through the use of a chiller. There are two different types of chillers. The first is a water‐ cooled chiller and is commonly used in buildings over 1,858 square meters and has become a common practice in commercial construction. An estimator must be aware that if a water‐cooled chiller is used, than a cooling tower must also be utilized on the roof.
Water‐cooled chillers produce higher tonnage (cooling capacity) at lower costs per ton, creating energy efficiency. The second type of chiller is an air cooled chiller. Though this type of chiller is not as effective as a water cooled chiller, it can be used when there is limited space inside a building. Air cooled chillers can typically be found in smaller office buildings and generally cost less, however they carry a higher energy cost.
Figure 3 (water‐cooled chiller) is an example of how a cooling tower helps release heat from the water to help cool the chiller.
Figure 3 Water‐Cooled Chiller
PUMPS
An estimator must be aware that for every piece of heating or cooling equipment, there is a pump that is needed to distribute water from the equipment to the heating and cooling coils of the air distribution equipment. This information may not always be communicated to the estimator. These pumps can vary in size depending on the size and load requirements. Typically two main primary pumps and a re-circulation pump for each of the heating and cooling system will be needed. The main pumps will feed the majority of the system while the re-circulation pump will help maintain the pressure of the system and return the water to be heated or cooled again. Along with the pumps, the estimator must allow for an air separator and an expansion tank for each system.
MAIN AIR SUPPLY EQUIPMENT
The most common piece of equipment that will supply air to a building is called an air handling unit. This is almost always used in a commercial building. The purpose of this piece of equipment is to move air from outside to inside a building and to heat and cool air through the use of hot and cold water coils. It also takes the exhausted air from the building back out into the atmosphere. An estimator will need to be aware there could be an energy recovery wheel that is included with the air handling unit.
This recovers heat from the exhausted air and reuses it to save energy. Energy recovery wheels can often be expensive so an estimator must ask if it will be part of the air handling unit system.
Figure 4 (air handling unit) is an example of how air will pass over the coils, thus transferring hot or cold water coils to the air.
Figure 4 Air Handing Unit
VARIABLE AIR VOLUME BOXES
A list of the major pieces of equipment is typically what the estimator will be given before the start of an estimate, however smaller pieces of equipment that are used to help enhance the system may not.
These pieces of equipment may not be shown on schematic design drawings and will have to be included based on the building type and the number of rooms. One of the most common methods to help enhance a system is to install variable air volume boxes (VAV boxes). These are small boxes that
are installed in between the duct-work. Variable air volume boxes come with different internals
depending on the buildings needs.
Table 1 (variable air volume box variations) shows the different
variations of these VAV boxes and the most common ones used for different types of buildings.
Table 1‐ Variable Air Volume Box Variations
Typically there is one for every two rooms. So if an estimator knows the number of rooms and the buildings use, one can accurately calculate the type of VAV box and the number of boxes that will be
needed.
SUPPLEMENTAL HEATING AND COOLING EQUIPMENT
It is common in buildings to have some areas that do not receive enough heat through the central heating, or that there simply is not enough insulation to contain the heat. To help supplement heat in these areas, small heaters are used. These include fan coil units, unit heaters, and cabinet unit heaters. These act in the same way as variable air volume boxes, however, they are not connected to the duct-work and can be placed anywhere in a building. These pieces of equipment can also be heated through the use of hot water pipes or through electric coils. Electric coils are the most common method used since it saves cost by eliminating having to run pipes to these units.
Common places to place such equipment are in areas such as stairwells, mechanical rooms, and entrances to buildings. An estimator must be aware that if a building has an elevator, than the building will also have an elevator machine room. This room houses all the elevator’s equipment's. This equipment tends to get very hot and requires the use of a split system air conditioning unit to help cool down the room. This unit is very similar to what is used in residential homes, but not as big. It consists of an outside condenser, inside fan unit that has cooling coils inside it and piping between the two.
HVAC EQUIPMENT OVERVIEW
Now that all of the components of the HVAC equipment have been covered and it is understood how they function, one can see there are many different variations and combinations of equipment that can be used to complete a system.
Table 2 (example of building equipment) shows how an estimator
can decide what other pieces of equipment will be utilized depending on building size, type, and number
of rooms.
As stated earlier, the designer has the ability to choose which system will be used. Being able
to identify the smaller pieces of equipment and knowing the different setups will help an estimator ask
the question, “What type of system are we using?”
EQUIPMENT PIPING
The second component of HVAC equipment system is the piping that is needed to carry hot and cold water to equipment coils. An estimator has to accurately calculate the quantity of piping that is needed. Again, past experience will help an estimator accomplish this challenge. In every HVAC system, there is a hot and cold water system. For each system there will need to be a supply and return pipe. This means for every piece of heating and cooling equipment, there are two pipes going to it. An estimator has to be aware that some pieces of air‐supply equipment have both hot and cold water running to it, so it will require two sets of piping.
QUANTIFYING PIPING
In order for an estimator to take off the quantity of pipe needed, one would have already established the equipment used to heat and cool the water, and the equipment needed to supply the water to the air distribution system. For example, an estimator would have already known if the variable air volume boxes would be using electric reheat coils or hot water coils. Once an estimator has the equipment quantity, an average length can be taken for each piece of equipment depending on the building size. Buildings less than 929 square meters will have an average length of 18.3 meters per set of pipe. Remember, there is supply and return piping for each hot and cold water supply. Any building over 929 square meters, 30 meters will be used. However, if the supply air equipment contains more than one coil, this number will be doubled.
Table 3 (piping quantities) is an example of a building
equipment list taken from table 2. This will show the number of coils and pipes going to each piece of
equipment and the average length that can be used to help an estimator come up with an accurate
quantity.
Table 3‐Piping Quantities
DUCT-WORK
All projects require the use of duct-work to distribute and return air throughout a building from the air handling units. An estimator that has worked on past projects that have been built can accurately quantify the amount of duct needed when it is not shown. Since duct is priced per kilogram, using past jobs will allow an estimator to figure out the kilograms of duct that will be required for a specific building type by dividing the square meter of the building by the number of kilograms. For example: a 1,858 square meter office building that was completed last year required 10,000 kilograms of duct-work. So that equates to 5.38 kilograms of duct-work per square meter for a similar job.
DUCT-WORK INSULATION
After an estimator calculates the kilograms of duct-work, one has to multiply the kilograms of duct by 70% to obtain the surface area of insulation. This is not a mathematical approach to the quantity of duct insulation, just a proven method among st estimators. Like the duct-work, this is where an estimator’s past experience is useful.
DUCT-WORK MATERIAL
When quantifying duct-work, an estimator has to keep in mind that there can be different types of material used. Typically, duct-work is made out of galvanized metal. Laboratories required the use of stainless steel duct-work. Stainless steel duct-work is used when there are chemicals in the air that are being exhaust. One example of this would be exhausted air from a fume hood. When estimating a laboratory, using 15% of the total duct will allow for enough stainless steel duct-work.
AIR DEVICES
In every building, there are diffuse-rs, registers, and grills used in the ceiling for the duct-work to connect to within the rooms. There is an easy method in quantifying these devices since they will not be shown. Typically every room will have two diffuse-rs, one for the supply duct and one for the exhaust. An estimator can easily get the number of diffuse-rs by multiplying the number of rooms the building has by two. This will include corridors, mechanical rooms, and electrical rooms.
CALCULATIONS
As you can see, the challenge for an estimator to accurately quantify the air distribution system is that they would have had to work on an identical building to obtain these calculations. Using these calculations and methods can help an estimator complete the air distribution system before it has ever been designed.
Table 3 (air distribution calculation) shows a comparison of different building types and
the amount of duct and accessories required per square foot. One will notice that a laboratory will
require more duct than a typical office building.
Table 4‐ Air Distribution calculations
CONCLUSION
Estimating a conceptual HVAC design can prove to be challenging. There are many methods estimators have adopted over the years to help accurately complete a system with limited information. HVAC equipment is one of the most important components in the system since it tends to have the highest overall cost.
Making sure an estimator has quantified all of these pieces is important since the other components such as piping are impacted by these quantities. Since the equipment affects the quantity of the piping, the equipment should be the first item that an estimator focuses on. After the equipment that will be used is established, an estimator can accurately quantify the meters of pipe needed using the methods disused in this paper. Knowing the type of building and how it will be used is very helpful to the estimate since this influences the amount of duct that will be required. Estimators with past experience, as well as using the techniques and methods discussed, can help provide accuracy when trying to estimate quantities for a conceptual HVAC design.
Top 7 Most Reviewed Mechanical and HVAC Estimating Software Systems
1. Maxwell Systems Estimation is an advanced estimating program that specializes in generating estimates and takeoff for HVAC, mechanical, and residential and commercial plumbing and electrical firms. We find the software to be a good match for firms that have annual revenue from $1 million up to $1 billion making it a solution your company grow with.
In addition to handling the takeoff and estimating capabilities of these trades, the system includes integrated functionality for project and service management. This allows for estimates and takeoffs to be performed while being able to track materials, forecast for projects, and manage service contracts.
The estimating application contains functionality for Excel integration, proposal generators, visual assemblies, “what-if” analysis, and a historical database. The estimation module includes trade specific estimation capabilities for each of the trades served to help generate the most accurate and financially feasible estimates possible. The software includes a database updated with the most current prices for materials and labor for each industry.
The application for digital takeoff includes functionality for electronic plan takeoff, digitizer integration, a conversion calculator, automatic scaling, and CAD file integration. The digital takeoff application allows for plans to be downloaded from any online plan room and generate takeoffs without the use of digitizer boards and stylus pens. For those that prefer digitizer boards, takeoff can be streamlined the takeoff with their Rollup Digitizer or Rigid Digitizer, which integrate with the system. The Rollup Digitizer is a lightweight digitizer designed by GTCO that was built for the field made to “roll up” into a carrying case. The Rigid Digitzer is their permanent fixture offering that digitizes takeoffs from a more standard digitizer board.
2. WenDuct and WenPipe are construction estimating and digital takeoff systems designed specifically for mechanical contractors. Wendes Systems, the maker of WenDuct and WenPipe, has a long history of helping specialty contractors create estimates. They were founded in 1976 and have published 30,000 copies of their Wendes Sheet Metal and Mechanical Estimating Manual. Today, they offer estimating software and input devices designed specifically for these trades including real-time, web-based net pricing, and rectangular to round conversions for value engineering sheet metal in order to lower costs.
WenDuct and WenPipe are designed for contractors working on HVAC sheet metal, mechanical piping, industrial ventilation, and process piping projects. It's best for small and medium commercial and industrial contractors.
The takeoff and estimating applications in WenDuct and WenPipe can be purchased as individual systems, or combined in a single system. The takeoff application offers screen takeoff from digital drawings, digitizer integration, automatic scaling, 2D takeoff, a conversion calculator, CAD file integration, and many other features. The estimating application offers Excel integration, an updated cost database, visual assemblies, a proposal generator, and more. The labor and material cost data in WenDuct and WenPipe is based on 22 years of productivity studies from Herb Wendes.
3. FastEST, Inc. is one of the industry's leading developers of takeoff and estimating solutions that have been specifically designed for plumbing, mechanical, HVAC and sheet metal contractors. For almost 20 years, FastEST, Inc. has worked to provide competitively priced software solutions that are both trade-specific and user-friendly. Their software is used by thousands of contractors of all sizes, both large and small; in fact, more than 30% of their customer base to date has an annual revenue under $2.5 million.
FastPIPE® and FastDUCT® are two of the company's easy-to-use, comprehensive construction cost estimating solutions. FastPIPE was designed to meet the unique needs of mechanical contractors that manage both industrial and commercial work. It supports a variety of estimates, from plumbing to industrial process piping, HVAC piping and insulation.
FastDUCT simplifies the estimating process for sheet metal contractors managing HVAC and industrial duct work. FastPIPE® was the first piping system to use the intuitive Windows interface in 1995 and FastDUCT utilizes the same platform. FastDUCT reports integrate directly into FastPIPE, offering an end-to-end mechanical bid quoting solution. Also integrated into both FastPIPE and FastDUCT is the company's On-Screen Digitizer, which offers users to complete takeoffs on their computer directly from digital plans and drawings.
FastEST maintains and updates the pricing in their database, which is unique among their competitors. They also offer in-house online and technical support.
We recommend FastEST solutions to contractors seeking a complete cost estimating solution that was designed specifically for their trade.
4. The On Center Software portfolio includes On-Screen Takeoff and Quick Bid. These solutions are the counterpart to On Center’s popular and free Plan-viewer which has seen over 200,000 downloads from N. America and locations around the world. The On Center system itself has been put to use by over 20,000 companies globally.
The On Center offering includes a takeoff and an estimating application that can be used by both commercial and residential contractors, including the trades of: design-build, general contractors, interior and exterior finishes, roofing, mechanical, electrical, plumbing, HVAC, low voltage, concrete, and many others. The takeoff application includes on screen takeoff, digitizer integration, file integration (CAD, PDF, etc), and 2D takeoff. The estimating application includes electronic quote system, cost databases by trade, and accounting integration. The system is compatible with tablet technology that provides field access to project data for cost and labor management.
Companies best suited for this product will bring in revenue upwards of $1 million and be of any number of employees. There is no limit to the number of users that can be added to the system so companies will be able to grow using the software.
5. Sage Estimating (formerly Timberline Estimating) offers integration with Excel, as well as RS Means. The software also supports conceptual estimating, and proposal generation. Construction firms interested in the construction estimating application will also likely want to purchase the construction takeoff application.
Construction firms that need one or more templates in their estimating software should avoid the starter package as it does not come with any templates in the estimating software. The software features a standard version, as well as an extended version that includes estimating templates. Both versions come with pre-built databases ready to use “out of the box.” Databases can be easily customized, too.
We find the capabilities of Sage Estimating fit the needs of construction firms across all segments. Whether you are a firm that specializes in utility contracting or mechanical and HVAC construction, the product can suite your needs. We find that the primary limiting factor here is revenue. Sage Estimating is best suited for companies that run operations of at least $1 million due to the Timberline software cost. Construction firms beyond this benchmark will find this solution to be suitable.
6. Vision InfoSoft currently has a customer base of over 11,500 electrical and plumbing contractors. Plumbing Bid Manager is the only industry solution that integrates automatic pricing updates with estimating and on-screen takeoff. Plumbing Bid Manager offers cost estimating and on-screen takeoff on a best-of-breed basis. The software includes key features such as digitizer integration, 2D takeoff, excel integration, and visual assemblies. The software also includes standard estimating features such as “what-if” analysis and conceptual estimates. To help plumbing contractors make the most accurate bids on their projects, the software includes an updated cost database with up-to-date material and labor pricing. Plumbing Bid Manager is best suited for small and medium-sized plumbing contractors, but can also support larger firms taking on projects beyond the million dollar mark. The software is a great fit for both residential and commercial plumbing, but does not offer support for mechanical or HVAC projects. Vision InfoSoft offers a unique training program with Brian Hoffelder to help buyers get up to speed with the software’s estimating functionality. In addition to the built-in training, Vision InfoSoft also offers support by phone, email, and Internet.
7. McCormick Systems was founded by a contractor during the late 1970’s and after thirty-three years in the industry has grown their product to reach over 8,000 contractors around the world - from the United States to Australia. McCormick System’s has won numerous awards for their estimating software from multiple trade organizations and publications.
McCormick Plumbing & Mechanical Estimating software was developed specifically to handle the needs of construction firms that operate in the plumbing and mechanical piping trades. The software’s strength lies in the estimating, takeoff, and bid management applications which are offered as best-of-breed solutions. For contractors that also get involved in a bit of service work, McCormick offers a best-of-breed service management application.
The takeoff application offers modules that allow for CAD file imports, automatic scaling, 2D takeoff, and digital plan takeoff. McCormick also offers a count and length probe that integrates with the software to allow manually marked drawing measurements to be entered into a digital format.
This package can handle jobs of nearly any size. We find ourselves recommending it primarily to companies that generate up to $100 million in revenue. There is no limitation on the number of employees or number of users to operate this system.
For contractors that need takeoff capabilities digitally, McCormick offers On Screen Estimating to perform takeoffs from PDF, TIF, JPG files and many more.
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