I'm looking for some insight into why HVAC contractors don't use the ACCA process for sizing and selecting HVAC and Distribution systems. I know part of it is the generational "I've done it this way for twenty years, and I'm not changing now" attitude, and some folks are apprehensive to anything related to a computer. But are there other factors that are at play that keep contractors from using the ACCA process? I'm wondering if it's something as basic as not understanding the value of properly sizing a unit and not undestanding how to explain that value to the customer. Many guys in my area think that running a Manual J takes far longer than it actually does. Any other insights would be appreciated.

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When a house is initially constructed the lowest reliable bidder typically gets the job. The lowest bidder can't work with slim builder margins and still pay an employee to run manual J calculations. Jobs are typically priced by the ton, so contractors don't have much incentive to downsize equipment. The best HVAC contractors in our area don't even accept low margin new construction jobs because they don't need the work.

Even w/o a full manual D "common sense" things are often missed entirely. Long duct runs are sized no larger than ducts right next to the furnace. Nobody thinks "hey it's a 25' run, maybe we should use and 8" duct instead of a 6". Rooms with a lot of exterior glazing/walls/cathedral ceilings don't get any more air than those with only one exterior wall.

Add to this that when a system does go down it's in the middle of summer/winter and contractors are very busy. Most just want to swap the unit for one of the same size w/o thinking about it. Customers call when HVAC systems can't keep up, not when they get blasted with cold/hot air.


I’ve found over the last 10-15 years that most HVAC companies do not have incentives to do things right. They get paid for larger equipment. Not enough trained personnel and equipment to do the right job; as doing all manual calculations by hand takes a lot of time, and there is a lack of training in new computer programs or computers for that matter.

Even for large companies that do have the knowledge, personnel and equipment, you have the old mentality of oversizing “just to cover the 1% percent of the time the climate is above or below normal”.

To be fair, builders have not helped themselves by building leaky and inefficient homes; and Architects and Designers are not far behind with a lack of knowledge and detailing for energy efficient drawings.

See a discussion I started a couple of few months a go: http://homeenergypros.lbl.gov/forum/topics/manual-j-report?commentI...


 not undestanding how to explain that value to the customer.

People want to avoid pain.  You need to know if they recognize the pain of poor HVAC design.  Start simple.  

Explain that building to code is building to the crappiest specification legally allowed.  Building a worse home could mean going to jail.  

Ask them if they've ever experience a home that had rooms that was frustratingly hard to heat or cool, experienced equipment that was so noisy they had to watch tv with the remote in their lap, and/or had a home with surprisingly high energy bills.  

Homes are not Corvettes, they are super tankers. Reorient they way they think about energy and comfort.  Fluctuating temperature means DIS-comfort.

Help them understand that comfort and efficiency aren't achieve by heating a home UP or cooling it DOWN, it's in MAINTAINING comfortable temperatures evenly and silently within the building thermal envelope.   The home loses or gains energy from the environment, HVAC helps remove or replace that energy.   In the nicest homes this is done in a way that is not apparent or even noticeable, it's just done.  

My clients report not ever having to touch the thermostat, and only thinking about heating and cooling when they open their bills and are surprised by how low they are.   The opportunity to get that right is never better than at design and specification.  That does not occur by building "to code".  

But remember, some people need to learn from their own mistakes.  Keep your antenna up for these people so you don't waste a lot of breath.  

My clients report not ever having to touch the thermostat, and only thinking about heating and cooling when they open their bills and are surprised by how low they are.

This statement is an important one, few customers have a home so comfortable that they aren't messing with the thermostat constantly. Even room temperatures help a lot with this also. The problem is most consumers typically buy a "spec house" that is already or mostly built by time they buy it. A few people custom build but they account for a minority of purchasers. This leaves builders to decide on which contractor to choose and what system needs to go in there. The builder/HVAC contractor are more interested at minimizing initial costs than optimizing comfort. If building code limited the size to HVAC units to something like 1ton per 1,000 sq ft (not unreasonable for new construction in most areas) it would force the builder to insulate the house properly or deal with customer complaints.

I couldn't agree more. Using comfort as a selling point is a huge opportunity. One thing I really like about Manual J softwares is that once the home is entered, you can see how other home upgrades like sealing the ductwork, adding insulation, air sealing, etc. can affect the heating and cooling loads of the home. It can be presented to the homeowner as a "a few hundred dollars spent here can save you this much on your equipment cost," and even if it's a wash on the front end, the lower operating costs are a positive cash flow in a few years.

Thanks for the feedback guys, very helpful.


The problem is customers have the idea they can "manage" the temperature INSIDE their homes.  This leads to crazy behavior that means the contractor has to field calls from uninformed people, for free.  

Fielding no revenue phone calls is not a sustainable business activity.  

My customers have aggressively small equipment.  It also has variable BTU output to further improve ability to load match.  I spend a great deal of time educating them, so they know that if they let the house drop 10 degrees it will take a day to recover.  They don't care about recovery, they'd rather have a home that is always comfortable (aka - supertanker) and 30% lower energy bills than their neighbor with the noisy and uncomfortable (aka - corvette) system.   

Most homeowners want recovery in 15 minutes, and think the key to saving money is to NOT heat and cool their homes.  

This backward thinking creates a major dilemma for the contractor.  

They have few calls about "bill is too high" or "house is clammy" or "equipment is noisy" or "daughters room is freezing" in which they get blamed.  I've seen all these complaints caused by oversized equipment.  

They get blamed when the house doesn't "recover" at whatever rate the homeowner thinks it should.  This is what happens with, what I consider, properly sized equipment.  

With no skin in the energy bill problem, their obvious answer is to oversize and avoid the "my house isn't heating UP fast enough" phone call.  Note, this is not "my house isn't staying warm," it's "my house is not GETTING warm."

Until we stop telling people "setback your thermostat and you'll save enough for college tuition" this problem of oversized equipment is not likely to go away.   

I am a HVAC Dealer  in a small town and I do load calcs and have for 15 to 16 years. I believe it has value but the lowest bidder will get the job in a large percentage of the bids.  My calc have been used by the homeowner to check if the others are pricing the same size equipment and then go for the lowest price.  They don't realize that sizing is just one part of the information a load calc contains.

Our local builders always go with the lowest cost system. 

My main business is correcting the previous work done by the so called "professionals"  Then the load calcs really come into play in determining sizing, duct and airflow shortfalls.  I like to compete against contractors that "don't know" and more importantly "don't care"

Thanks Steven, that's just was I was looking for. I was mainly asking the question in a changeout scenario. Even if a homeowner has no clue what a load calculation is, seeing one contractor take the time (and seriously, are we talking about more than an hour for the majority of homes if you're using software) to run the calculations and then go over the main points, compared to a guy who looks at the unit and throws a price out. It seems that using the Manual J as a sales tool can really differentiate the professionals from the rule of thumb only guys.

Granted, you have no control over the homeowner taking your quote and getting a low-bid guy to undercut you. But I'd hope that the time you put in can establish some trust and hopefully some loyalty, as well.

Thanks again.

Trust is the big issue - people buy the low bid because they dont trust the better system is worth the money -after all if I am going to get screwed I want lose $5  rather than $10.   They (not all) do call us when it doesn't work well or they cant find the low bidder any more because he wont answer his phone or is out of business.  I have had two customers in the last year have us redo their system within 6 months of buying it from someone else. In one case the homeowner paid as much to redo the ductwork as they paid for the initial system.  They are  one of our best cutomers now.  

Quality will win out over the long haul if you can survive the short haul.  After all no one ever got yelled at for doing it right or going beyond what was expected.

Here is your opportunity to shine. Sell the customer on additional services that you provide with your bid. Offer to fix ductwork or other obvious issues with your quote. This way when the homeowner comparisons shops and sees the other contractors just want to "swap and go". Your quot needs to explain why you aren't the cheapest, but will offer the best overall value to your customer.

I already do that and a lot of customers see it up front and others have to experience the dark side of hvac  lol.   .  to be honest, we all make value judgements on what we can afford and if given knowledge and choices up front people will make an informed choice and do what is best for them not always what I think is best for them.  Either way I always leave the door open so when they do want to correct things we will be an option for them.  It is a slower path but at least I don't have to duck people on the street.

As a BPI BAP/EP, NATE certified technician, Mechanical Contractor, and a member of RSES, and ACCA, and ICC, I can safely say, Manual J, D, and S are great, as are all of the manuals....but, they often do not allow for real world situations. The problems arise and are exaggerated when you are working on very old leaky houses, being lived in by people without a lot of money. When these people want it to be 70 degrees inside with an outside temp that is 10 degrees above the Manual J summer design temp., there will be problems. Air sealing and insulating a home this old and leaky can be very expensive, widows are even worse. Barely usable roofs and basement/crawlspace, moisture are also possible. Unless these people can afford to make extensive repairs, Manual J will not help. The existing equipment can barely keep the space below 90 as it is. The customer will not accept a smaller system. It is far cheaper to the customer to purchase a system the same size or larger than it is to make extensive structural repairs.

The old saying "the customer is always right" is absolutely true. Tulsa OK has a summer design temp of 97 degrees and yet we hit 115 degrees. The temperature was above 104 degrees for days at a time.

I have met far too many people that have no experience in the real world, but do have a BPI certification. These individuals have no business touching or giving advice on mechanical equipment. One of my technicians performed a service call for a customer that had a BPI Analyst accidentally knock down two sections of flue pipe that he had drilled through first. While they were waiting the "analyst" explained in detail how bad the job was and how there was obviously not a Manual J done on the equipment. My technician informed me this was a 7 year old 3.5-ton system on a 2500 sq. ft. house, with lots of windows and a cathedral ceiling. there was no identifiers as to who installed it, but it was an average system install that was properly inspected. He did not do a load calculation obviously, but based on experience I saw no red flags. I later performed an energy audit and found the system was properly sized and the ductwork in the attic had R-6 insulation. There were obviously sealing and insulation opportunities possible, and even a possible efficiency upgrade, but realistically they upgrades were not worth it to the customer, with the exception of duct sealing, which was minor.


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