Q: We had a handyman doing some work around our house last week, and he told us that he thought many of our problems with uncomfortable rooms and high energy bills were the result of duct leaks. He then said the biggest thing to worry about was potential backdrafting problems when we use our fireplace or gas stove, and we should get the ducts fixed right away. Was he trying to scare us or is there something here to worry about?
A: This seems to clearly be one of the major energy issues in homes that isn't keeping pace with the many other improvements in products and building strategies and so it remains a potential problem for many people.
While I've written often about ducts, I don't think I've addressed the backdrafting issue before so I think it's worth talking about this subject.
You already know that your heating and cooling system is constantly recirculating air throughout your house, and if the ducts are not tightly sealed, these leaks can draw in air from the attic, garage and other places in and around your home. This means that pollutants like car exhaust and stored chemicals in the garage, dirt and mold in the crawlspace and pollen and insects from the outdoors can get into the duct system.
But there's another issue involving leaky ducts that has a potential more serious effect on your health. Ducts that are not properly sealed can cause depressurization of the home and as a result, when you use fuel-burning appliances or your fireplace, leaky return ducts near combustion equipment can cause backdrafting of the flue gases in furnaces, space heaters, water heaters, wood stoves and fireplaces.
This is a situation that happens when gases from the combustion equipment are drawn back into the house rather than being expelled to the outdoors, creating a potential dangerous problem indoors.
Contractors know the importance of this and most do a good job of sealing the ducts, but if holes and tears occur over time, leaky ducts can depressurize the area near the furnace. The result is that the backdraft could possibly put carbon monoxide and other dangerous fumes into the home.
Because ducts are sort of hidden up in the attic, it's hard to see them to make sure they're properly sealed. They're also fairly easy to tear or rip when you're inspecting or sealing them. And they typically have many turns and bends that need to be well-sealed and sometimes aren't tight even after they're first installed.
I suggest that you make sure you have carbon monoxide detectors in your home, especially near each bedroom. Inexpensive ones are available in hardware and building supply stores and can be easily mounted on walls or just plugged into electrical outlets. They'll alert you if this dangerous gas, which is colorless and odorless, builds up in your home. But if you're concerned about the ducts causing this problem, get them inspected.
It's fairly easy for leaky ducts to cause pressure imbalances in a home. I've read estimates that the air pressure in ducts can actually create as much as 25 times more air leakage through an opening than the same size hole would cause in a wall of the home. Leaky ducts can be a major energy-waster in a home, but they can also cause some potentially dangerous situations when they bring in dangerous gases that should instead be flowing out of the home. If you suspect that the ducts in your home are not well-sealed, don't put off getting them inspected and fixed.