One challenging aspect of duct renovation is accounting for everything that affects a successful outcome. These can be overwhelming. So much so, they can keep an HVAC company from adding air-side repairs to their service offerings because the owner doesn’t think the “juice is worth the squeeze.”

However, if you break all the variables down, you can place them into four familiar categories. This removes some of the unknowns and connects what is left to items you encounter daily. Let’s look at four factors that influence duct renovation and what you should know about them.


1. The HVAC Equipment

The first factor is the HVAC equipment. Equipment is what most people think of as the “HVAC system.” However, equipment and system are two very different things. HVAC equipment is the Btu factory component that delivers heating and cooling into the duct system and finally into the living space.

If the HVAC equipment is wrong from the beginning, it’s like building a house on a cracked foundation. Regardless of the equipment manufacturer, this component must handle the building’s heating and cooling loads. That doesn’t mean bigger is better. It means you should use industry-approved sizing methods like ACCA Manual J and S to determine the right fit.

Depending on duct location, duct losses often hide oversizing. If you’ve ever had a customer ask for a 5-ton unit when the 3-ton they currently have is already too much, you know what I’m talking about. Don’t rely on your customer's experience of “it’s always worked great!” to influence your equipment selection decisions.

Correcting a duct system on oversized equipment can be a costly mistake that you’ll regret. You will own the oversized equipment for a long time unless you address it first.

Don’t start a duct renovation if the existing HVAC equipment is oversized.


2. The HVAC Installation

The second factor to consider is the equipment installation. On an existing job, this factor mostly includes variables the installing contractor determined. Once your company steps in, you determine the fate of the duct renovation and the equipment’s future performance.

Since we’re talking about duct renovation and HVAC installation, the duct system is the obvious place to start. Once you know the right equipment is in place, you need good duct design to assure equipment Btus makes it to the living space in the proper quantities. The industry standard for this process is ACCA Manual D. Use it to aid you in duct fitting selection, sizing, and routing.

Once you design the ducts correctly, don’t forget to seal them to keep the air inside and avoid losses. Other factors include balancing dampers for airflow control and duct insulation to limit air temperature losses. Finally, choose the right registers and grilles to complete the installation.

Additional aspects of an HVAC installation include items we often take for granted. These include:

  • Refrigerant lines, insulation, purging, and evacuation;
  • Controls and electrical wiring (line and low voltage); and
  • Condensate disposal and safeties.

Your craftsmanship determines how the system installation comes together. Unfortunately, it doesn’t always get the attention it deserves.

Your installation determines duct renovation success as much as the equipment you use.


3. The Building

The third factor in any duct renovation is the easiest to overlook. That’s because we often don’t associate it with the HVAC system. The building can make a substantial difference in overall comfort. If it is messed up, your customer cannot get the full benefits of duct renovation.

Consider this: You can have a perfect HVAC system, but a bad building will beat it every time. That’s because you can’t control what you can’t contain. The building is a Btu container, and Btus equal comfort. So if the building leaks or has poor insulation, it isn’t a very effective Btu container.

Many in our industry believe the building is someone else’s responsibility. Most times that is true. However, if there’s a comfort complaint or humidity issue, the framer or insulator doesn’t get the call — you do.

The easiest way to understand the building is to look at it as an extension of the HVAC duct system. The traditional side of the duct system includes the ducts, dampers, insulation, air-handling equipment, sealants to prevent air leakage, registers, and grilles. However, the building is the extension of the duct system that connects air from the supply registers back to the return, creating a closed-loop system.

Just like a traditional duct system, the building has ductwork (rooms), insulation (in the floors, walls, and ceilings), and dampers (interior doors). The building should also be free of air leaks to contain and control the air inside it.

The building might be out of your work scope, but you need to understand how it can affect the outcome of your duct renovations.


4. The Customer

Make sure the customer understands your test results. If they don’t, they will resort to what they understand — price.
- David Richardson
curriculum developer and trainer
National Comfort Institute

The fourth factor in a duct renovation might not seem that critical, but it is the most important. The customer is the one who ultimately decides whether you do a duct renovation or not. If they don’t buy, it doesn’t matter how good you are at this stuff.

First, the customer must trust you. One way to help establish this trust is to put them in control of their HVAC system and the outcomes you can provide. Give them an experience that no one else can repeat. Testing makes a big difference in this relationship since most of your customers appreciate proof and something they can see. Seeing is believing, and that leads to trust.

Each customer knows their home better than anyone else, even you. After all, they lives there every day. Why not use testing to make them detectives in their own homes? Let them find their problems and guide them to the answers and solutions only you can provide. Testing removes all doubt and provides clarity and transparency to your customers.

Testing also helps determine which of the first three factors are most out of whack and need the most attention. They can see the readings from their own HVAC equipment, system, building, or a combination of the above. You may choose to include some tests at no charge, while more advanced testing should require an investment to continue.

Each test you offer should have an outcome or reason for taking it. Otherwise, you’re wasting time. There are some great applications on the market, like MeasureQuick, that simplify testing and guide you through the steps. They translate the technical aspects of our industry into simplified explanations with visual charts.

Make sure the customer understands your test results. If they don’t, they will resort to what they understand — price.


Juggling the Four Factors

If you try to consider all these factors at once, they can be overwhelming. You may try but end up doing nothing. This is a normal response, so don’t feel bad. The reason is “paralysis by analysis.” It is a response that originates in a part of the brain that controls subconscious behavior. You can read how it affects HVAC system performance and duct renovation here.

Because of all these conflicting thoughts and options, starting is the biggest obstacle. It doesn’t have to be that way if you decide to focus on progress over perfection. You learn by doing. So pick a place to begin and focus on taking one small step forward.

If you’re struggling with where to begin, start with what you know — the HVAC equipment. It’s one reason, at the National Comfort Institute (NCI), we recommend starting with static pressure and temperature at the equipment. You and your team are already familiar with it, so the first step isn’t that intimidating.

Next month, we’ll look at five rules to help your duct renovations flow smoothly and account for the four factors we discussed this month in a way that helps you and your customer agree on the best solution.