DIY Duct Leakage Test With Artificial Smoke

When you perform a duct leakage test with artificial smoke, you’ll be amazed at the leakage that exists.

Even with good-looking ductwork. Imagine that every joint is a hairline crack. Add up all the joints and connections; before you know it, you will have the equivalent square foot hole in your duct.

Using artificial smoke will help you find leaks in duct work. It’s a simple DIY project and the artificial smoke is not expensive. Simply turn your heating systems fan to the “fan on” position and while holding the smoke generator introduce the smoke along all the duct seams and connections.

On the supply or leaving air side of the furnace the air leakage will divert the smoke making leaks obvious. On the return side (filter side) the smoke will be sucked into the system.

The smoke generator I use in this short video is called a Wizard Stick. Amazon says they are currently not available but that changes. I found a similar unit called a Handheld Smoke Stick Draft Detector Machine.

Duct work leaks are one of the most energy consuming problems in most heating and air conditioning systems. Adding high efficiency equipment to a duct system full of leaks is not the answer.

You are way better off fixing the duct leakage and keeping the low efficiency furnace unless it’s just time to replace the furnace anyway. Sealing and insulating your duct work will give you a positive return on the cost of closing up all the cracks.

One Major You Should Do A Duct Leakage Test

These flex connector facilitate the connection between two sections of duct or duct and a furnace as you can see above. They are assembled by folding at the corners and then stapled at the canvas-like-material that provides the flexing.

You could have more than one flex connector. They also help eliminate vibration originating from the equipment. Just do a duct leakage test everywhere you can access the duct work.

The stapled part most always has a significant leak. Do your duct leakage test where these ends meet and seal them with a good pliable duct sealer or caulk.

You should seal up all the leaks as you find them. You will notice the system to run quieter as you begin to get all the leaks stopped. An added benefit.

Older Duct Work In Attics And Crawl Spaces Are Prone To Leak

You may have to get dirty and get down in that crawl space to examine your ducts. Look for sagging duct and flex duct that has separated from the metal connections.

If you physically are unable to inspect your duct work find a youngster who can and send them down there with a camera. Or, hire someone. It’s that important.

Animals like rats, mice, and cats love to snuggle into the warm spots especially on flex duct and scratch through the liners into the duct itself creating huge leaks and very unsanitary conditions.

The only way to repair such an invasion into flex duct is to replace the entire section of duct.

Mastic Duct Sealant Works To Seal Most Metal Duct Connections

Mastic duct sealing products are a great way to quickly close up those air leaks. It paints with a brush like paint and it’s water soluble. It will dry in no time and lasts for a very long time. I love using this stuff.

The image below shows me testing an elbow on a section of duct that I haven’t put mastic on completely.

It’s a little hard to see the leak moving the smoke, but it does. Each one of these connections is a small leak. The gores (the joint in an elbow) that allow the elbow to turn or adjust are also each, a small leak.

Add up all the connections or joints in a system. Even though they are only hair line cracks they add up.

The average thickness of a hair is about 1/1000 of an inch. Considering that heating system might have about ten 6″ elbows and 6″ elbows are almost 19″ around.

If my math is right, that adds up to an accumulated 1″ hole in your ductwork, those are the leaks in just the elbows. Would you go drill a 1″ hole in your ducting? Or spend $25 and buy a bucket of mastic? There are a ton of products made to seal ductwork. Check them out on Amazon; any of them is better than leaky ductwork.

Sealing Ductwork From The Inside An Alternative To A Duct Leakage Test

Years ago, I’m guessing around 2002, we were investigating a new product on the market called Aeroseal. It was a pretty exciting way to seal ductwork from the inside. No need for a duct leakage test after using the process Aeroseal developed.

We used my house as a test house, and I could not believe how much of a difference this process made on the efficiency and noise level of my HVAC system.

Aeroseal is an application that blows a polymer through the inside of your duct system. Nothing is introduced into the house as all registers are closed and sealed. This polymer finds all the cracks and crevices and seals them.

It’s an amazing process. Search for Aeroseal near you and get some prices.

Caution, 100% Duct Sealing Can Reduce Efficiency

Some duct systems are undersized from the get go. Sealing a duct work system that doesn’t properly distribute the air could cause overheating in winter and frozen AC coils in the summer.

Best test to have done is a static pressure test. I have an article that addresses static pressure here. Check it out. I discuss adding more efficient filters and how they can cause problems to systems that aren’t capable of moving enough air to compensate for such filters.

Conclusion

Nothing can compare to having a correctly sized duct system that is sealed properly and puts the correct amount of air into every room. Doing a duct leakage test yourself or hiring it done is a good start to doing your part in cutting cost.

Every day you wait to do this duct leakage test is money down the duct and out the crack. You are either heating the attic or the crawl space, depending on where your duct is located in your home.

If your return is in the attic then you are sucking in hot air in the summer and paying to cool it again or you are sucking in cold air in the winter and paying to heat it again.

If your supply ducts or the duct work delivering air into your house is leaking then your house will be in a negative pressure sucking in outside air that is unconditioned.

Many things in a home affect pressures in a house created by leaking duct work, and you should get the picture by now and be inspired to do a duct leakage test and seal up the leaks in your duct work.