Forced air systems use a series of air ducts and registers throughout your home to push warm air from the furnace in the winter and cool air from the air conditioner in the summer. Even if you have the most energy efficient furnace and AC unit on the market, it’s only as good as the duct system within your home.
Getting rid of air leaks by sealing ducts can improve the energy efficiency in your home but at what cost? Is it worth it? Let’s take a closer look.
Here are 7 secrets about air duct sealing you should know about and why ducts leak in the first place.
What are air ducts and why seal them?
Air ducts are the hollow metal tubes and enclosures that start in the basement or wherever your furnace is located and run throughout your home to each room and up from the floor to deliver warm (from the furnace) and cool (from the air conditioner) air to moderate the temperature inside the home. The Heating, Ventilation and Air Conditioning (HVAC) system in your home uses the air ducts to deliver conditioned air that has either been warmed or cooled depending on the season throughout your home.
Air ducts are known to cause a loss of anywhere from 25% – 40% of heating or cooling energy
so even the most expensive high efficiency furnace won’t be able to make up for this energy loss. If you have ducts in your attic and live in a very hot, humid climate it’s possible you’re losing energy at the higher end of this range.
Air ducts can leak because of poor design or damage to the duct work most notably. Energy loss during the heating or cooling process tends to be conduction of heat from the process itself and from air leaks. Many air leakage occurs at the connections to the air return registers, plenums or branches in the air duct system which often can’t be seen by homeowners and thus is difficult to notice.
Fixing air duct leakage will reduce energy costs and help your air system run more efficiently.
How do I know if my air ducts are leaking?
The common symptoms of leaking air ducts include:
- Noticeable damage or gaps to the visible air duct work in the basement.
- Air is coming out of the ducts in certain places that you can visibly see, hear, or feel.
- Your air conditioner or furnace runs virtually non-stop.
- You see dust in your rooms particularly near the air return registers.
- There is inconsistent heating or cooling throughout the home ie. varying temperatures in different rooms.
- Poor air quality within the home.
Sealing air duct leaks can help to solve each of these problems.
What is duct sealing?
Traditionally, duct sealing used methods to seal leaks in duct work from the outside. It typically involved sealing gaps and leaks with aluminum duct tape, duct work mastic and duct work insulation. This form of duct work sealing costs around $300 and many people will simply do the patchwork themselves.
Research and real life experience over decades has shown however that duct tape generally doesn’t last very long. Over time with the duct work alternating between sending warm air in the winter and cold air in the summer, the fluctuating temperatures causes the tape to eventually loosen and fall off. So even though it’s called duct tape, it may not perform very well on ducts, certainly not to fix leaks.
The first aerosol-based sealant was then created in 1994 at the Lawrence Berkeley National Lab to spray directly onto duct leaks by Dr. Mark Modera. He then commercialized the product by forming Aeroseal Inc.
What is Aeroseal?
Aeroseal is a Chicago-based company that provides residential and commercial duct sealing services. They created a new form of duct sealing that seals leaks and gaps with a sealant but from the inside of the duct work. They pump a water-soluble and low Volatile Organic Compound (VOC) sealant into the duct system from their truck outside the house through a tube throughout your home’s duct system and each register to seal gaps and holes.
This repair only works on damage and gaps that are less than 5/8″ so holes that are bigger than this will need to be repaired before duct sealing takes place. The work is guaranteed for 10 years after application although the company says they’ve stress tested it up to 40 years.
How much does it cost to seal ducts?
Professional duct sealing services such as Aeroseal range from $1,500 – $4,000 and up depending on the size of the home and thus the duct work size and any factors specific to your home that can add to the cost.
In terms of the benefits, Aeroseal refers to potential savings of 20% – 40% off your energy bill for up to $850 in savings per year which is based on government studies on the effectiveness of duct sealing.
Aeroseal’s services may be 3 – 4 times the cost of other forms of duct sealing services.
Does duct sealing work?
Consumer Reports stated back in 2012 that sealing air leaks in duct work and to a lesser extent in walls and windows offers the quickest savings in energy costs.
Aeroseal provides real-time reporting as the sealing work is being done which monitors the work in each room of your house. Aeroseal also provides a detailed audit report before and after the duct sealing to show you the air loss in Cubic Feet Per Minute (CFM) before you had the work done and again after the sealing has been completed. You can thus monitor the before and after results of your air loss.
If you have a hole in your ducts greater than 5/8″ in size, you’ll need to have this repaired first as duct sealing won’t work. If your duct work is already in bad shape and nearing replacement, duct sealing is likely a waste of money. The company providing the duct sealing should do a visual inspection of your duct work before agreeing to seal your ducts.
In some homes, your builder may have used cheap workmanship and parts or may have installed duct work that is actually undersized for your home. The inspection before doing the duct work might reveal that you’re better off replacing the existing duct work with a properly sized installation because in this case, duct sealing won’t solve your problems.
Duct sealing providers may include more than just actual sealing of duct leaks and may improve other aspects of your energy inefficiencies such as air sealing services to prevent air from flowing into the home. Indoor air quality, a reduction in your energy bills, poor airflow from registers, uneven temperatures in parts of the home, and overall improved system performance are all areas you should ask any duct sealing company about to see if and how they can help you.
Is duct sealing worth it?
Generally costing between $1,500 and $4,000 depending on the size of the home and duct work, the cost of professional duct sealing is not cheap and might be a significant percentage towards simply replacing your entire duct work system. Flexible polyester, flexible aluminum and galvanized steel are commonly used to build duct work so your choice can affect the cost.
If you are expected to replace your duct work system anywhere from 10 – 25 years after the home was built (more on that below), it would be difficult to financially justify duct sealing if your home is already 15 years or older as you might be approaching the date of having to replace the duct system. At that point of the age of your home, you’re probably better off getting an HVAC pro to look at your existing system to see what shape it’s in.
If you can’t afford professional duct sealing or aren’t quite sure it’s even worth it, you might consider a professional energy audit first and get a readout of your home to learn about how you use energy and where you’re losing energy. The professional report that you should receive can then give you guidance as to what you should do next.
Bonus questions
How much does it cost to replace duct work completely?
Some professionals suggest that duct work should be replaced every 10-15 years on the short end and every 20-25 years on the high end. According to Carrier, the average home has 30-90 linear feet of duct work but it’s based on the size of the home and number of rooms. You’ll typically find one register (vent) in an average sized room like a bedroom or bathroom and two vents for larger rooms over 100 square feet in size.
The need for duct work replacement is often due to noticeable damage and wear, mold and mildew growth. Other HVAC problems that a professional inspection reveals could be caused by the duct work itself and where repairs, duct cleaning or sealing won’t suffice.
Replacing duct work generally costs $35 – $55 per foot so a home with 30 – 90 linear feet so the total cost to replace your existing duct work could be in the $1,050 – $4,950 range.
Does duct tape seal air duct leaks?
While duct tape can be used to patch noticeable holes or small gaps that you can visibly see in duct work, most duct work in the home is unseen by home owners and thus can’t be patched or fixed. Studies have shown that many types of duct tape fail within days of being applied and thus aren’t suitable for repairing duct work despite the tape’s name.
Is air duct cleaning worth it?
Air duct cleaning is a somewhat controversial question because while air duct cleaning companies will tell you to clean your ducts every 3 – 5 years, others tell you not to bother. There is no scientific evidence that duct cleaning improves the health within a home although a service like Aeroseal may require duct cleaning prior to duct sealing taking place.
When else might you consider having air ducts cleaned? If you’ve had messy work done in the house such as wood flooring installed, a finished basement or some other renovation that involves sawdust or other debris flying around, cleaning your ducts can make sense. Your ducts can get dirty in this instance and you might feel the effects if you or a member of your household suffer from allergies.
If you have a bad odor coming from a duct or air return that smells like a dead animal, duct cleaning may also be a good idea. We experienced that at our house and other than that reason, I probably never would have thought about paying $250 for a duct cleaning but we did. It got rid of the smell but when I asked the duct cleaning company what it was, they checked the cleaning bag in their vacuum and couldn’t find anything of note other than dust and other debris.
Beyond that, you might skip the duct cleaning and save your money.
Before you pay for a duct sealing service…
Contact your local utility companies
Contact your local utility companies and enquire about the cost of doing an energy audit and ask if they subsidize it which some do.
The cost of a professional energy audit will depend on the size of your home among others factors but you should expect to pay in the range of $200 – $700. It can go much higher depending on what else you might have tested given the size and scope of your home.
Visit the RESNET website and learn about the HERS Index
Also check out the RESNET (Residential Energy Services Network) website to learn more about the Home Energy Rating System (HERS) Index which is the industry standard to measure the energy efficiency of homes.
The higher your HERS Index score, the more energy efficient your home and potentially the better the resale value should you put your house up for sale. It’s a very detailed report that covers various aspects of your home related to energy use, loss and efficiency including your:
- Walls and floors
- Ceilings, roof and attic
- Foundation and crawlspace
- Windows and doors
- Vents and duct work
- HVAC systems, water heater and thermostat.