Residential load calculations have been made easier with computer software. (Courtesy of Taylor Engineering LLC, Alameda, Calif.)
Apparently, contractors who do not perform residential load calculations would prefer to be anonymous. Whether they think they really should be doing load calcs, or whether they simply don't want to hear from people who think they should be, the respondents to ourNEWSonline poll largely did not identify themselves if they didn't perform load calculations on residential jobs.

The number of respondents (48) does not result in a statistically significant survey but does serve as a good indicator that may reflect commonly held beliefs of other contractors. Almost 38 percent of those who responded to the informal poll did not use any form of load calculation, and others implied they were not using industry-recognized procedures. It is likely that many more HVAC contractors did not wish to reveal the fact that they are not performing standard load calculations.

There are many reasons for contractors not to do them: "The methods are too complicated for residential applications, I can't do it without a computer, I don't trust the results, the results don't match the equipment you can get, I don't have time, the rules of thumb work well enough, I can't take time to go to the classes, my customers say they aren't comfortable with a smaller system," etc.

It might be true. It might point out the need for a load calculation method that falls in between the complicated equations and hold-up-your-thumb (or similar) joke methods. It might even point to a need for some stricter building codes. But it definitely gets people riled.


John J. Dubecky of Climate-Tech Inc., North Ridgeville, Ohio, is one of the contractors who responded to our survey. He said the company's selling technicians are required to perform "a short-form Manual J" that is "checked for accuracy once per year."

"Mine take approximately 20 minutes after I have collected the house measurements," Dubecky said. "I do have a short Manual J form that I use and it consistently is within 10 percent of the full load calculation form. I do not market this benefit to the general public, but we do inform all our customers that this is the correct procedure for the proper sizing of their equipment."

Although he knows it's the right thing to do, he has found that there have been drawbacks. "I have been doing them before the close [of the sale] and it has cost me plenty," Dubecky said. "I am repricing my equipment to sell before I design. This way I do less work for nothing in return.

"When I do my load calculations prior to the sale, I never leave the information behind unless customers are willing to pay $300 for the load calculations. I have had no takers for the 300."

"The load calculation is an unpaid consulting task and does not have a retail market," said Fred H. Kobie, owner of Kobie Kooling Inc., Fort Myers, Fla. "The calculation is an option on all of our replacement work, but it's rarely selected. We do demand it when the structure has changed."

Brian Baker, president of Custom Vac Ltd., Winnipeg, Manitoba, has known the pain of having his load calculations taken by the customer to another contractor. "They would take the information we gave them, and they would shop it. Lots of times a customer takes that information and shops it."

What may frustrate him even more, are "the customers [who] want a price on the phone. They do not want you coming to their house. Other people will shoot ‘em a price, some of them over the phone."

Baker said he believes that changes to equipment, particularly modulating systems, help compensate for the lack of load calculations, at least preventing problems such as air conditioners only running long enough to satisfy the thermostat without dehumidifying the air.

"We now are selling air conditioners and furnaces that are either two-stage or using modulating capacity. So you go ahead and do a heat loss or heat gain calculation, and you put in the high-end product, and 99 percent of the time it's never going to be at that capacity. The equipment is adjusting for the flow.

"I can see at some point in time, we're going to have something that is very much plug and play - hook it up just like your computer," Baker continued.

"It's done and you walk away. It consumes the energy it needs for that day, and that's gonna be the end of it."

However, the customer may not get the energy savings they may think they should be getting. With energy costs as high as they are and no sign of them slowing down, customer awareness of energy consumption is at an all-time high.

"We've got people thinking about the way gas prices are going," Baker said. "They are starting to think about these [HVAC products] things."

"We bought our first load calculation program in 1989 and have been doing loads on every new house style ever since," said Rich Krider, president, Howell's Heating and A/C, Ashland, Va.

"I think there are several reasons why contractors do not do loads; the biggest are probably time and money."

Krider said a lot of the equipment suppliers have been enabling contractors who can't or won't do load calculations.

"The contractor doesn't have to educate themselves on how to do one, they don't have to invest in the software or take the time. The equipment supplier will tell you that they don't do loads for contractors, but that simply is not true. If you open shop today, there will be two to three suppliers at your door willing to do whatever it takes to ‘earn your business' and increase their market share. Of course you are now obligated to buy their product."

Lennox territory manager, Scott Ansley, of the company’s Troy, Mich. office demonstrates how quickly data can be entered for a residential Manual J load calculation.


The complexity of today's load calculation procedures may contribute to residential contractors' reluctance to do them. That and a lack of consumer knowledge of load calcs are the main reasons they are not performed more often in residential replacement work, said Glenn Hourahan, vice president of research and technology, Air Conditioning Contractors of America (ACCA).

"Contractors may fear a complicated, time-consuming procedure," he said.

"Yet, in terms of doing things right ... it takes a few minutes to factor in building components, orientation, and location for a correct load calculation. It takes a few more minutes to make the proper equipment selection. A bit more time and a proper duct design (using an appropriate friction rate to size the air distribution system) can be undertaken as well. All of these items are vital steps for properly designing a central system. Many contractors note that today's advanced HVAC software allows them to do the ACCA system design process in less than one hour."

"The more detailed they've made the loads, the fewer the number of contractors who are performing them," said Ted Boyle, senior territory manager, York Air Conditioning, a Johnson Controls company, and a former HVAC technician.

"I won't design an HVAC system of any size without doing a load, but I don't know of any contractors who feel the same way. At this point, they can't do a load without a program, three days of schooling, a lot of practice, and going to church after all the cursing they did. So guess what they do? They resort to square footage rules."

Moreover, "Consumers don't know they can and should demand a high-performance standard from their HVAC contractor," Hourahan said.

"Rarely do residential consumers link problems such as uncomfortable levels of humidity, high utility bills, high dust levels, and/or poor indoor air quality to a substandard design, improper equipment selection, subpar installation, or incomplete commissioning.

"Lack of understanding causes consumers to consider first-price-only, when making purchasing decisions about HVAC equipment," he continued.

"Contractors who serve first-price-only consumers, sadly, fail the customer and the HVAC industry. If these contractors fail to design correctly, how can they be expected to deliver high performance and properly installed equipment offerings (e.g., reduced energy use, less environmental pollution, less dependence on foreign fuels, enhanced comfort, improved occupant productivity, proper occupant safety, better temperature and humidity control, etc.)?"

In the replacement market, "Many contractors think someone else did the load calculation," said Hourahan. "They will further assume that it was done correctly." If the contractor asks whether their old system kept them comfortable and the consumer says yes, "the contractor simply puts the same thing back in without verification of proper equipment sizing, system design, or applicability."

Simply asking whether the homeowner has made other home improvements, such as a new roof, insulation, or windows, could tip off a contractor that a load calculation needs to be done. A smaller resulting system would cost the customer less, and the system prices would be lower.

"If the system actually needed to be smaller, many contractors would hesitate to downsize the system - especially if the customer expresses satisfaction with the prior unit - as they are fearful of the inevitable ‘can't cool' calls on the hotter summer days," Hourahan said.

"Who in the world took all that weather data and then decided to satisfy the customer most of the time?" asked Boyle. "Americans believe in being satisfied 100 percent of the time, and will kill any contractor who tries to talk them out of it.

"I used to work for a contractor who designed by the book, and on the really hot days we were inundated by customers with no-cooling calls," Boyle said. "We would send a serviceman out, who was only able to verify that the unit was operating normally, and the customer would then angrily quit us."

"Everyone knows the programs got too sophisticated since Manual J Version 8," said Rob Falke, president, National Comfort Institute, Sheffield Lake, Ohio. "Basically, you can get the program to agree with any size equipment that you want."

Done correctly, load calculations contain a wide assortment of information about any particular structure. Many residential HVAC contractors question how much information is actually needed for them to figure an accurate residential load. (Courtesy of Taylor Engineering LLC, Alameda, Calif.)


"We teach a ‘Manual Rob' duct and load sizing program, as well as room-by-room airflow calculation as a sales tool only," Falke continued. It was not created to be a substitute for Manual J or D, he said - but the company felt a real need for something to get contractors to estimate a load.

"At 20 seminars we asked how many jobs, other than new construction, had a J or D calculation done, and the answer came in every time at two to three percent," Falke said. "So we devised methods of field engineering on a sales call that tons of guys and gals use. Basically we derived some typical parameters for the conditions that affect load the most. This helps the guys do abbreviated field engineering."

As far as what can be done, "Go back to the basics and keep it simple," Falke said. "But I think that's impossible, it got too fancy and that moved it out of the reach of the contractor.

"Good contractors will do them when they need to. What has really happened is that since the program got muddied up, many good contractors did a few calcs and learned the rules of thumb, figured it out and then simply applied those rules to every ‘quick calc' they do. They could care less about what anyone else says about them or thinks of them.

"The goal is to downsize equipment so it can run longer, dehumidify more, and use less energy," Falke said. "You don't need a full load calculation to do that."

"The duct design, or lack thereof, is a bigger problem in Florida," said Kobie. "Either way, making the load calc a requirement would cause more contractors to circumvent the permitting process - not the desired affect. The free market force and the tort cases that involve the contractor that does not perform the tests will eventually cause the market to change the contractor. It will take time, but it will happen."

Many people say that when replacement HVAC load calculations are required in residential codes, then they will be performed. However, the experience in new construction work has been less than encouraging.

"Building inspectors do not rigorously enforce the code, although doing a load calculation is a [new construction] requirement in nearly every jurisdiction," said Hourahan.

"Contractors take this as a clue that since building inspectors do not require a load calculation, then it must not be necessary. Electricians and plumbers are not fighting this type of battle within their industry sectors. They have to size properly, and code inspection enforces it."

Hourahan cited these examples of a lack of professionalism within the residential HVAC industry:

  • "Manufacturers, distributors, and utilities give lip service to doing proper load calculations, but then provide shortcut sizing procedures that do not support the same. Where do you think the rules of thumb came from in the first place?

  • "Contractors think that since the competition isn't doing a load calculation, they don't have to either. Contractors are fearful they will lose a customer on price considerations. However, it is the price-focused contractor who is the lowest common denominator, who misleads about quality and performance, and who destroys the image of the HVAC industry."

    "I have heard rumors that some localities are requiring a load calculation with [residential replacement] permit application," said contractor Krider. "That may help but it isn't going to convince anybody to do it. You do it because it's the right thing to do."

    "If it was required to get a permit it would be done more often," countered Russ Donnici, president of Mechanical Air Service Inc., San Jose, Calif.; "or if the contractor got stung by having installed too large or too small a system, which created a noticeable change in the indoor comfort that the client could feel and subsequently had to replace the system. It's always more impressive when it hurts your pocketbook."

    Baker said government subsidies once gave his customers an incentive to have load calculations performed. When the subsidies were reduced or removed, customer interest dried up. "The program when it first started was $350. We didn't have a problem getting people to do it." He said green building or LEED for Homes programs could generate more consumer interest in the United States.

    "We need to get more contractors doing loads, by generalizing the inputs," said Boyle. "We don't need a million different factors for basically a handful of genuinely different types of walls."

    In short, "Properly sizing equipment is like exercising and eating seven servings of fruits or vegetables daily," said an anonymous manufacturer's employee. "Everyone knows they should do it yet no one does. Why? Because it's hard, it's not a habit, and there's no immediate reward to doing so."

    "In the end, it is the consumer who is the driving force," said Hourahan. "He pays the bills and receives the benefits. Ultimately, what it would take is an educated consumer who will not be satisfied with poor performance. Consumers are becoming more educated and more demanding. Informed consumers are increasingly less tolerant of hot and cold rooms, damp or dry living conditions, or noisy, drafty heating and cooling systems.

    "Contractors need to overcome their fear and serve their customers," Hourahan said.

    "Consumers do not want low cost; they want high value; which may come at a slightly higher price. Many contractors recognize this today and have built thriving businesses based upon providing value in their service offerings and adding more time in their job to cover the needed work and associated costs."

    A seminar on "Residential Load Calculation Practicality" will be held June 28, 2006, during the ASHRAE Annual Meeting in Quebec City. For more information, call 800-527-4723 or visit Please send comments on this topic to; Barbara Checket-Hanks c/o The NEWS, 2401 W. Big Beaver Rd., Troy, Mich. 48084.

    Sidebar: Survey Results



    * Several respondents' replies implied that they were not using industry-recognized load calculation methods. Some also may have been responding as commercial HVAC contractors.

    Types of load calculation methods cited by some respondents:

  • Trace 700 using gbxml import from AutoCAD

  • Wrightsoft Manual J8

  • Trane Manual J

  • Excel program self made

  • Psychrometric charts

  • A short-form Manual J is used and checked for accuracy once per year.

  • Our selling technicians are required to do the load calcs.

  • Static pressure

  • Manual J worksheet

  • Block load

  • Computer-based software

  • Practical rule 500 Btuh per square meter

  • Manual J8AE (half hour, easy form)

  • Quick Loads pro software

  • Wrightsoft Right Suite 6

  • ASHRAE method

    Publication date: 06/12/2006