Bad and Leaky Ducts Raise Your Electrical Bill

Air leakage and escaping from your duct system can have a very poor effect on your Air Conditioning System, reducing efficiency, reducing lifespan, and reducing the overall performance of the system.  Air duct leaks can increase your energy bills, create a lot of allergen excessive dust, and cause poor indoor air quality for You, Your Family, and Your Pets.
In order to fully understand how air duct leaks and a leaky duct system can cause your Air Conditioning System to operate inefficiently, it is important to know how the duct system works in conjunction with the Air Conditioning System to heat or cool your home.  We will use the example of cooling your home, rather than heating, because we have such harsh summers it helps put things into perspective.
When you turn on your A/C at the thermostat during the summer this is what is happening and the steps that it happens in,
1. the unit turns on and a motor turns a fan to suck air through the “return” ductwork to the inside of your unit.
2. The air from inside your home is sucked in through that “return” duct and passes over a filter to catch dust particles. ”The common filter you change monthly”
3. The air is then blown over a coil that is made of copper and aluminum, and looks similar to a giant radiator.  “That coil has refrigerant inside of it that cools the coil ice cold in the summer.”
4. The air gets sucked through that coil and cooled down.
5. After the air gets sucked through the coil and is cold, it gets pushed out the other side of your unit into the “supply” ductwork.  “The ductwork is either made of metal tubes or rectangular boxes that are connected together in sections, or it can be flex tubes that are like a giant slinky wrapped in insulation, or sometimes a combination of both.”
6. The air travels through the “supply” ductwork and is spit out of all the different registers / vents in your home.

You also have a “return” duct that connects to a filter box and grill.  Larger homes have multiple return ducts, each connecting to a box with a filter grill.  In many cases, those “return” boxes are leaking at the seams and at the main connection collar where the ductwork is attached.

The return ducts may also be leaking at other connections in the ductwork, and at the main connection at the air handling unit. “The Unit Typically in your Attic or Closet”
Air Conditioning Systems are designed to pull air from the inside of your home, over the filter to remove particles, and blow it over the coil to be cooled and distributed back to your home.
If the return duct has any leakage it causes some of the air to bypass the filter.  That means that the Air Conditioning System is sucking in some air from your home and the filter is catching the particles, and some of the air is sucking in through all of the seams, gaps, and holes in the “return” ducts from the attic. The quality of Air in the attic is very poor and is full of dust and debris, as well as fiberglass insulation that you don’t want to breathe.
Also, just so you know attic air in Tallahassee Florida is usually between 120-170 degrees in the summer which is much hotter than the typical 75-85 degree air inside your Tallahassee home.  Making your Air Conditioning System have to work much harder to cool down 120-170 degree attic air, rather than 75-85 degree home air.
Any average eskimo can quickly figure out that this reduces the lifespan of the Air Conditioning System and increases your energy bills and Joe does not like that.
Air Conditioning Systems are also affected by the particles that bypassed the filter.  You don’t want to breathe the attic air full of dust and fiberglass, and neither does your Air Conditioning System.
The air from the attic gets blown over the coil to be cooled, and that causes the coil to sweat condensation.  Some of the dust and fiberglass particles from the attic air end up sticking to the wet coil, and it creates build up, sort of like a lint trap in a dryer.  Most manufacturers recommend that you clean the indoor coil every 2-3 years, and APS and Energy Star recommend cleaning it every 2-4 years, but with leakage, it needs to be cleaned more often.  Cleaning the coil is difficult and costly, so sealing the duct work will help keep that coil cleaner.
When the coil gets residue and build up, it causes the motor to run harder in order to suck the air through that coil because it’s impacted with debris so the airflow is restricted.
When the motor runs harder, the amp draw increases, and so does your energy bill, not to mention the fact that it reduces the lifespan of the motor.
The dust and fiberglass particles that make it through the coil are pushed through the “supply” ducts and distributed in the air throughout your home.
Those particles also build up in both your “return” and “supply” ducts as well.  So if you have leakage in your “return” ductwork, it creates poor indoor air quality, an increase in dust throughout the home, an increase in your utility bills, and it reduces the efficiency and lifespan of your air conditioning system.

As with leakage from your return ducts there can also be leakage from the “supply” ductwork.
Supply side leaks are usually also found at connections, as well as the seams and gaps inside the main trunk line, distribution boxes, or the “supply” boxes that have the registers / vents attached to them.  So after the air is sucked through the unit and cooled from the coil, it travels into the supply ductwork and some air just blows into the attic.  So besides cooling down your home, you’re also cooling down your attic, which is a waste of money.

The other issue is that the leakage from the supply ductwork will cause a vacuum effect on the home.
A five ton unit is made to suck in 2,000 cfm of air through the filter, and spit out 2,000 cfm through the registers.  So if that five ton system has 10% air leakage from the “supply” ducts, it’s sucking in 2,000 cfm, but it’s only blowing about 1,800 cfm into the home, and 200 cfm into the attic.  The unit still needs to suck in 2,000 cfm, and since it can’t get all of the air back that it spit out because 200 cfm went in the attic, it causes a vacuum in the home.  That vacuum pulls in warm outside air from doors and windows, and it also pulls in dusty and polluted air from behind electrical outlets and switches, as well as from any gaps at plumbing penetrations, light fixtures, ceiling fans, recessed can lights, and so on.  So once again, the leakage is affecting your indoor air quality.


Sealing air duct leaks in your duct system is usually an all day job, and in some cases it may take 2 or 3 days if the home is large or you have to make frequent trips in and out of the attic because of the heat, remember 120-170 degrees, If you attempt this Job yourself Joe recommends you bring plenty of ice to the party and make sure that you stay hydrated, the technicians at Tallahassee Air Conditioning & Electrical are used to doing this kind of work and their bodies are conditioned for it so please be careful.

The total cost to make the necessary repairs depends on the size of the home, the type of ductwork used in the system, the amount of air leakage detected during the negative pressure test, and the overall condition of the duct system.  The cost can be as little as a few hundred dollars, or as high as several thousand dollars.

Our home comfort specialists seal all of the supply and return ductwork in the attic at all seams, connections, and collars using a high temperature fiberglass reinforced elastomeric sealer.  We also seal any distribution boxes and trunk lines at seams, collars, and end caps using the same sealer.

Our specialists then remove all supply registers / vents and seal the ductwork from the inside at seams, joints, collars, and connections with a high temperature fiberglass reinforced elastomeric sealer.

We will then fill up any gaps in the drywall behind the registers using a silicone latex caulk, and reattach the registers, inside all return boxes at seams and collars with the sealer, and fill up the gaps in drywall around the filter grills using a silicone latex caulk.

There are a ton of variables that can come into play that will require additional sealing.
⦁ Duct systems that use return air platforms may require plating off areas using duct board or sheet metal and sealing over the plates.
⦁ Systems with fresh air return ductwork also usually require plating off areas and sealing over the capped section with sealer.
⦁ Sometimes leaks in the duct system are located at torn or deteriorated flex duct runs, or damaged hard duct runs or distribution boxes that cannot be properly sealed.

In those cases, we replace or repair the ductwork as needed, and proceed with sealing the ductwork after making the repairs.

Some homeowners have conditioned air loss from the shell of the home, referred to as the home envelope.  In some cases, customers request that Tallahassee Air Conditioning & Electrical make the necessary repairs to reduce the conditioned air loss as well as seal the duct system.

Our specialist can explain the benefits of sealing the home envelope after performing the negative pressure test, and inform you of the priority of the repairs, depending on the issues (allergies, asthma, COPD, dust, warm or cold rooms, energy consumption, etc.) each customer is concerned about the most.

There are a variety of repairs that can be made to the home to help reduce conditioned air loss, ranging from replacing leaky can lights with air tight can lights and sealing around plumbing pipe penetrations and installing weather stripping around door frames, to sealing inside electrical outlets and switches and sealing around speakers, sky lights, and light fixtures. Realize that a lot of times Tallahassee Air Conditioning & Electrical is unable to repair the issues we locate, such as replacing a leaky window.  In those cases, our specialist will inform you of the problem, and recommend a company that can perform the repairs.


Apr 3, 2016 Uncategorized

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