HVAC Ductwork: Best Practices for Cleaning, Modifying and Care

HVAC Ductwork: Best Practices for Cleaning, Modifying and Care
Arne Jacobsen
Residential Sales Professional

I have been in heating and air conditioning trade for 44 years. In that time, I have installed, serviced, designed ductwork, sold, and sized thousands of residential heating and cooling systems.

About This Article

Your ductwork is the circulatory system of your HVAC system. Proper sizing, cleaning, care and maintenance of home ductwork is important to maintain efficiency and comfort.

Your HVAC system includes an air conditioner (or heat pump), a furnace, a thermostat, maybe some air quality products like humidifiers or air purifiers, and...what else??

Oh right, ductwork!

Ductwork is too often the forgotten element of HVAC systems. This is a mistake, because it does a LOT.

To put it into physiological terms, if the main equipment represents your organs (thermostat = brain, furnace = heart, etc.), your ductwork is the circulatory system that connects everything and allows the organs to do their job.

So what exactly do you need to know about ductwork? You set it up and forget about it, right? Well, not quite.

All HVAC equipment can be hyper-efficient or a drain on the entire system. Ductwork is no different. So we’re going to cover a few areas, and when you would want to consider each one:

  1. Ductwork Cleaning - the when, the why, and the how
  2. Ductwork Modification - the when, the why, and the how
  3. Ductwork Care - the whe...you get the idea!

What’s in it for you? Reduced energy costs, fewer allergens in your home, cleaner air, and more comfort throughout the year. Hopefully, that’s enough to interest you. If so, read on.

Ductwork Cleaning

You’ve probably done a bit of ductwork cleaning yourself when you drop a coin down a vent or your son or daughter inspects an open vent and somehow a baseball ends up inside of it.

This isn’t quite what we’re talking about when we refer to ductwork cleaning, but we’re going to come back to it, since inspecting your vents can be useful.

Dust, dirt, grime, and other contaminants will get into your ductwork over time. This, in turn, affects airflow, air quality, and your health.

So we need to clean it. How do you do this?

The first option is with a roto brush. This is basically a vacuum cleaner with an extended hose and a rotating brush on the end. The brush agitates the particles in the duct, and the vacuum sucks them up.

This can work well for some situations, and in fact is a great solution for mildly to moderately dirty ductwork that needs some attention beyond routine system maintenance.

Roto brushes can’t always reach everywhere, though, and for systems that are heavily clogged or very dirty, another level of cleaning is required. For that, you need a professional power vacuum.

A power vacuum is a massive vacuum that’s attached to a truck. The vacuum line is inserted into your ductwork, and other vents are closed off or otherwise sealed to create a pressurized environment. The entire system is then suctioned to perform a deep cleaning.

Power vacuuming also frequently includes a longer, more malleable agitator that can reach into the deepest regions of your ductwork to loosen debris.

At Fire & Ice, we don’t perform power vacuuming, though we do offer roto brushing services that are often of great benefit to our customers. For larger cleaning jobs, we’re partnered with a local power vacuuming company whose commitment to excellence matches our own. In situations where a power vacuuming is required, we refer customers to this company.

So to reiterate, when should you get your ducts cleaned? When your HVAC partner recommends it based on debris buildup and system performance.

Why should you? Because debris can cut down the dimensions of your ducts, which inhibits airflow. This makes your system work harder, which shortens its lifespan. It also increases your energy bills and gives you dirtier air than you deserve.

How should you? By working with a vetted company that performs thorough system cleanings.

Many of the same considerations go into ductwork modification, which we’ll talk about next.

Ductwork Modification

Did you know that a new system installation sometimes requires modified ductwork to accommodate it? Well, now you do. Let’s talk about why this is.

A Manual J Load Calculation should be performed on your home when installing new equipment. This process, which is created by the Air Conditioning Contractors of America, is designed to get the right power level or “size” for your air conditioner, heat pump, or furnace.

A Manual D calculation works similarly, except for ductwork. Based on the cubic feet per minute (CFM) moved by your system through the ductwork, it’s power/size, the velocity of the airflow, and a few other factors, the Manual D will let an HVAC contractor know what size ductwork should be.

If your previous system was very old, or a previous HVAC installer performed the Manual J incorrectly (or didn’t perform it at all!), you may require ductwork modification.

RELATED: Cost of HVAC Ductwork Modification

As an aside, the Manual D calculation can be performed with a tool called a Ductulator. That’s not necessarily relevant for you as a homeowner, it’s just a funny-sounding word. I thought you might like to know. Moving on…

What Is Static Pressure, and Why It Matters

So you have a balloon and begin blowing it up. For a while, the balloon is insufficiently enlarged and will appear small and saggy. Put too much air into the balloon, though, and it will pop.

That’s static pressure, except on the insides of ductwork.

Why should you care? Because an improperly sized duct system will give you a saggy balloon (or a popped one). You could spring leaks with too much pressure, or have pockets of dead airflow with too little.

Other factors contribute to static pressure, such as how dirty your air filter is, how dirty your ductwork is, and sometimes even the quality of the installation of your blower motor (usually found in the furnace or air handler).

Installing flex duct

Types of Ductwork

There are a few main types: metal, flex duct, and wood. Wood is the least common. At Fire & Ice, we generally install metal ductwork, but will occasionally use flex duct in conjunction with metal ducts.

Flex duct is the most flexible, as the name suggests, which makes it great for tight spots in the home. But it has some downsides. For starters, it’s the most fragile. Adjusting or cleaning it requires extra care.

It also has ridges on its insides, which trap dust and debris more easily. Flex duct will often get dirty faster than metal ducts.

We tend to use it only as needed due to logistical constraints as a result of home construction.

The construction and installation of any type of ducting matters, though, for a couple of reasons:

  1. A 90-degree turn will produce more static pressure than a curved turn, which can damage the system.
  2. Hanging ductwork properly can prevent it from sagging, thus producing areas that act as dirt traps.

A knowledgeable HVAC installer is the key to all of this. A bad installation or modification is going to produce numerous problems. A good one will prevent them.

HVAC ductwork

Ductwork Care

This sounds great, you might be thinking, but it’s all on the contractor side. That’s true enough. So what can you be doing to ensure the health of your ductwork?

Several things, it turns out. Let’s run through them:

  1. Replace and/or clean your air filter on its recommended schedule. No, this isn’t ductwork, but it affects the static pressure.
  2. Periodically survey major ductwork for any cracks or holes that might indicate leaks and, more holistically, too-high static pressure inside the system.
  3. Keep an eye on those vents (remember I said we’d come back to them?). If airflow stops or dramatically slows down from one or more vents, there’s a problem.
  4. Also, look for dust and dirt inside the vents or coming out of them. This can indicate unhealthy air and clogged ductwork.
  5. Schedule routine maintenance for your HVAC equipment. This usually means twice a year; once for the furnace, once for the air conditioner or heat pump. If you have noticed any problems mentioned above, talk to your maintenance technician about it. They’ll be able to diagnose the problem.

Heating and cooling vent

Indoor Air Quality Concerns

Hopefully, we’ve impressed upon you the need for good ductwork. It’s important for us to mention, though, that it’s not just us who says this. The previously-mentioned Air Conditioning Contractors of America (ACCA) have a whole section devoted to air quality issues in their Manual D calculation instruction manual.

A few snippets from this section are below, which discuss the risks of poor duct sizing:

“Comfort is compromised when infiltration (of outdoor air) creates drafts. Infiltration also can cause the indoor humidity to be too high or too low…

“Also note that when leakage is associated with the return side of the duct system, it can have significant effect on the operating characteristics of the HVAC equipment…

“Health can be adversely affected when duct leakage produces a condition (infiltration or negative pressure) that draws pollutants (dust, dirt, spores, fumes, odors, vapors, sewer gas, soil gas, radon gas, etc.) into occupied space…

“Duct leakage can have a direct effect on the pressure within the house, within the various rooms of a house and within the buffer zones that are associated with the house. In some cases, this leakage can cause negative pressures, which have an adverse effect on combustion appliances, fireplaces, flues, and vents…”

This is just a sample from a much larger manual, but we hope it gets the point across.

The Master Bedroom HVAC Problem

So let’s pull this out of the abstract and into your home. Let’s say your master bedroom is very hot in the summer (this isn’t an uncommon problem). What’s the cause?

Is it ductwork? Maybe, maybe not. But your ductwork is a good place to start.

Sometimes, due to home construction, the cost of ductwork modification is prohibitive. In these cases, you’d want to look into alternative solutions, like a mini-split.

RELATED: Ductless Mini-Splits 101: What They Do & How You Benefit

Other times, a thorough duct cleaning will allow proper airflow to the bedroom.

Still other times, you might really require larger or more ductwork to properly heat and cool the room. This usually occurs when a home is constructed and isn’t properly measured for HVAC ductwork. Inadequate ductwork to a room can produce hot and cold spots.

So long as the home’s construction doesn’t prohibit the addition or expansion of ducts, a good HVAC contractor should be able to install or modify your system appropriately.

A worst-case scenario here might be that your ductwork is adequate, but the core equipment (A/C, furnace) wasn’t sized properly at installation, and it would require a brand new system to get the proper airflow to that room. Most times, though, a less expensive solution is possible.

Either way, ductwork modification gives you options for optimal comfort.

Ductwork components

Let Your Home Breathe Easy

What did we call the ductwork earlier? The lungs of your system? Or maybe the circulatory system?

The exact metaphor isn’t the important part. The important thing to remember is that without correct ductwork, nothing’s going to heat or cool your home like it should. And the potential risks mean that you may be inviting contaminants into your lungs by not properly fitting your ductwork to your HVAC system.

The solution is obvious: be aware, be informed, and talk to your HVAC partner when it comes time for either maintenance visits or it’s time to replace a major component of your system. You won’t be sorry that you did.

Need to get in touch with an HVAC contractor? Are you in the Greater Columbus, Ohio area? Give us a call to get things started. We’re looking forward to making your day better!

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