The Value of Design and Right-Sizing by Arlington HVAC Contractors

The Value of Design and Right-Sizing by Arlington HVAC Contractors

Before the not-so-cold winter arrived in Arlington this year, we were looking at the importance of heating, ventilation, and air conditioning (HVAC) contractors.

In this post we return to the subject of contractors, who wear many hats, including:

  • salesman
  • installer
  • problem solver
  • service and repair tech
  • trusted advisor
  • designer


Design, as it turns out, is one of an Arlington HVAC contractor’s most important important jobs and is often overlooked because most homeowners think of an HVAC contractor as more installation and service tech than designer.

HVAC 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 HVAC contractors in any state such as Texas or cities such as Arlington, but they do call attention to an issue homeowners should be aware of, especially when calling a contractor to install new heating and cooling equipment.


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

HVAC 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 is easily seen throughout Arlington.

In 1975 the average home was 1,645 square feet. Today it’s nearly 2,500 and it’s not uncommon to see homes (sometimes called McMansions) 3,000 to 5,000-and-more 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 Arlington HVAC service, repair, and installation contractors to properly “size” the equipment.

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

”Wrong-Sizing” Scenarios

Here are a few scenarios to understand.


This is where an Arlington HVAC company, 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 without any regard to how it will fit and operate in your home’s environment.

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 that this approach works well because of their experience upgrading systems over years of operation.

“Square Footage”

Similar to “nameplate.” In this scenario an Arlington HVAC company, 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 may have worked well 30 years ago but 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 Arlington HVAC contractors or ones in the Metroplex reply on “rule of thumb” calculations, but homeowners should be aware of the practice regardless. Ask how calculations are made.

”Right Sizing”

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

Arlington homeowners should insist on “right sizing.”

If “right sizing” is not offered by an Arlington HVAC contractor, find one that does.

In some cases, it’s possible, that the Arlington HVAC company works with gas and electric utility companies in Arlington, Fort Worth, and Dallas, who also do right-sizing assessments and calculations.

Also check with nearby home improvement centers for recommendations.

Manual J

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

There are self-proclaimed 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 contractor not only “right size” but use the Manual J specification.

The Design Process

The Arlington HVAC company, 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-valueof 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.

Benefits of Right-Sizing

“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 Arlington homeowners should NOT do when choosing an HVAC contractor.