Air Conditioning in Arlington: Contractors as Designers

Air Conditioning in Arlington: Contractors as Designers

Heating, ventilation, and air conditioning (HVAC) contractors wear many hats . . .

  • service tech
  • repair tech (there is a difference between service and repair, although these can be the same in some companies)
  • salesman
  • installation tech
  • problem solver
  • trusted advisor
  • designer


What does an Arlington air conditioning contractor have to design?

This post takes a look at one of the contractor’s most important jobs, something that many homeowners simply overlook because they don’t know its importance.

Contractor as Designer

Think about this for a moment: More than half of the heating and air conditioning systems installed in the U.S. are the wrong size.

This surprising tidbit not only comes from a bunch of national surveys but from the mighty Department of Energy.

Surveys contend that more than half of HVAC contractors do not properly “size” heating and cooling systems, which means homeowners:

  • are paying for over-sized equipment (and associated installation costs) they might not need
  • believe their HVAC is operating efficiently when it’s actually inefficient, costing more to operate and impacting comfort
  • may be experiencing a “clammy” feeling in their homes and/or unseen and unhealthy mold growth
  • may be experiencing uncomfortable and large temperature swings
  • may have equipment that “short cycles” without realizing it
  • may have equipment that requires more-than-usual maintenance and/or service and repair

The surveys do not single out contractors in any specific state like Texas or cities like Arlington, Fort Worth, or Dallas, but they do call attention to an issue homeowners should be aware of, especially when calling an Arlington air conditioning contractor to install new heating and cooling equipment.

Wrong-sizing Background

“Wrong-sizing” isn’t necessarily a new phenomenon, but it’s one that shouldn’t be happening as frequently today because of all the technology and knowledge available to prevent it.

Air conditioning equipment has been under- or over-sized for decades, but contractors and builders were doing the best they could with the technology and knowledge available at the time.

But, over the past 30 years, homes have dramatically increased in size through renovation and large-scale new construction, which are easily be seen in Arlington and neighboring communities.

In 1975 the average home was 1,645 square feet. Today it’s 2,434 and it’s not uncommon to see homes (often called McMansions) 3,000 to 5,000 square feet. There’s also been a shift from single-story to two-story homes, which necessitates additional equipment to handle the upstairs living area.

The increased square footage and architectural complexity of homes today also makes it more difficult for service, repair, and installation specialists to properly “size” the equipment.

This does not mean HVAC contractors are crooks or incompetent. Not at all. But if you encounter companies that offer to install heating and cooling equipment without performing load calculations, based on current industry standards and practice, then find another contractor.

”Wrong Sizing”

Here are a few scenarios to understand.


This is where a service technician, installation specialist, or salesman reviews the metal tag on existing equipment. The tag lists Btu per hour output, among other things, and that information is used to sell you “one just like it” or, worse, a bigger unit.

This approach doesn’t take into account any improvements made to the home since the HVAC’s original installation or any worsening conditions or mistakes make during the previous install.

You may also hear from contractors this approach works because of their experience upgrading systems over years of operation.

“Square Footage”

Similar to “nameplate.” In this scenario a service technician, installation specialist, or salesman asks you for the living-space square footage. He bases his recommendation on a typical value like one ton (12,000 Btu/hour) is needed per 500 square feet.

This approach does not take into account the differences in home orientation, design, construction, energy efficiency, or intended use.

“Rule of Thumb”

Similar to “square footage,” “rule of thumb” involves adjusting the square-foot rule so whatever equipment the contractor has in the warehouse becomes the “right size” for your needs. “Rule of thumb” calculations, which are actually illegal, are based on outdated information and performance specs using high, medium, and low guesses. They often translate into a one-size-fits-all solution.

It’s not that all Arlington air conditioning contractors or ones in Fort Worth or Dallas don’t apply ”rule of thumb” calculations, but homeowners should be aware of the practice nonetheless.

”Right Sizing”

“Right sizing” requires much more information (see below) and is offered by conscientious air conditioning contractors. It’s particularly important to “right size” in Arlington and North Texas because of the brutally hot summers.

Insist that your Arlington air conditioning contractor, service or repair tech apply “right sizing.”

If “right sizing” is not offered, find another contractor. Or, in some cases, it’s possible, that the company works with gas and electric utility companies in Arlington, Fort Worth, and Dallas (who will do the right-sizing assessment and calculations) or even major HVAC manufacturers in the area. Also check with nearby home improvement centers for recommendations.

Manual J Standard

Manual J, published by the Air Conditioning Contractors of America, is the most common standard used to calculate residential load requirements.

There are so-called user-friendly (that’s debatable) computer software packages available to consumers who want to calculate load requirements themselves, but you’ll still need a good understanding of HVAC terminology and systems and know something about construction and math.

Insist the Arlington air conditioning contractor you are considering not only “right size” but use the Manual J specification.

The Process

The service technician or installation specialist (not the salesman, unless he’s a certified tech) will . . .

  • Measure walls, ceilings, floor space, and windows in each room for accurate dimensions and volume. Room by room assessments allow “estimators,” as the service techs and installation specialists are also known, to understand the “air tightness” of the space and to better estimate air flow requirements.
  • Take into account the R-value of the home’s insulation, the solar-heat ratings of windows, and other building materials.
  • Perform blower-door tests, if applicable, for air leakage.
  • Take into account other variables like skylights, fireplaces, ceiling heights, and how many people live in the home, among other things.
  • Review ducts and ductwork (and seal, if needed) and design solutions with distribution in mind.
  • Test for performance, including duct tightness, room-to-room pressure, delivered air flow, and the a/c system charge.


“Right-sizing” according to Manual J standards benefits the homeowners in several ways.

  • Peace of Mind. The equipment, including brand, model, and SEER rating (among other features and functions), has been properly sized and may be smaller and less expensive.
  • Efficiency. Right-sized equipment operates more efficiently because it’s been designed specifically for your home’s environment and characteristics, not on “nameplates” and guesstimates, saving on energy costs.
  • Fewer Repairs. Right-sized equipment requires fewer repairs and lasts longer, assuming basic service and maintenance check-ups are made.
  • Healthier Home. By reducing cyclic losses, humidity control is improved and, with proper duct design, you will have a much healthier and comfortable home.

Next Up

Next, we’ll look at things for Arlington, Fort Worth, and Dallas homeowners NOT to do when choosing an HVAC contractor to replace old equipment.