By Ted Ballantine
When it comes to household safety, there are a few simple measures that nearly every homeowner takes: locks on the doors, smoke alarms on the ceilings, and carbon monoxide detectors on the walls.
But there is one occurrence that even the most astute homeowners can fail to plan for: backdrafting, a potentially deadly phenomenon that can turn your home into a hub for dangerous gasses – without you even knowing it.
What causes backdrafting? And what can be done to prevent it? We talked to Nick Gromicko, founder of the International Association of Certified Home Inspectors, to find out.
What Is Backdrafting?
Every home has appliances that utilize combustion; fuel-fired water heaters, furnaces, boilers, and more. But homes are meticulously designed to make sure the dangerous by-products of combustion get sent outside through a flue. Backdrafting, explains Gromicko, happens when that system breaks down.
Backdrafting begins when “the pressure differential that allows for release of combustion gases is overcome by low indoor air pressure, caused by a high rate of expulsion of air pushed outdoors, through exhaust fans, fireplaces and dryers, ” says Gromicko. “Then, combustion gases can be sucked back into the house and may even cause death to the occupants.”
Gromicko recommends getting a proper, knowledgeable, licensed home inspector into your home if you are worried about backdrafting in your home. The right home inspector can look for clues, inspect your flues and find any kind of flue blockages in your home, and recommend safe ways to fix or improve the air quality in your home too.
Get the Story Straight on CO Detectors
A carbon monoxide detector is a simple way to detect – but not prevent– backdrafting.
Unfortunately, a recent survey found that most homeowner do not understand how to use their carbon monoxide detectors properly. This can include when to change the batteries, replace the unit, what the various alarm sounds mean. Take the time to read the instruction manual that came with your unit. Proper installation is also key to get proper ratings, as many units suggest not placing near the furnace. If you are unsure about where to place your carbon monoxide detector unit, or just have questions, you can always call your local fire department for information.
It’s worth stressing again that carbon monoxide detectors can tell you if you have a problem; but they aren’t preventative.
Here are some of the most common causes of backdrafting:
Install Your Gas Water Heater Properly
In the backdrafting world, gas water heaters are often suspect #1, warns Gromicko.
“Consumers have to be worried about fuel-fired water heaters. They shall not be installed in a room used as a storage closet. Water heaters located in a bedroom or bathroom shall be installed in a sealed enclosure so that combustion air will not be taken from the living space.”
When it comes to installing your gas water heater, make sure you have properly checked for any gas leaks in the line, and of course, have vented it properly.
Don’t Seal Your Home Too Tight
Today’s homes are sealed up quite nicely, keeping the warm air inside when it’s cold out, or the cool air inside when it’s hot out. We all love to save money on our heating and air conditioning bills, but too much of a good thing can turn bad: tightly sealed houses can severely exacerbate pre-existing backdrafting issues.
Properly Configure Your Flues
Fuel-fired water heaters, boilers, wall heaters, and furnaces are designed to exhaust the by-products of combustion to the outdoors through a flue. Another way dangerous backdrafting can occur is “through improperly configured flues, or flue blockages” warns Gromicko. Having a home inspector check to make sure your that all your flues are installed properly, in good working condition and do not have any blockages is vital to avoid backdrafting in your home.
Properly Vent Your High-Efficiency Furnace
When replacing your older furnace for a newer, high-efficiency model, you will probably have to convert and change the venting system. If improperly installed, or venting system is not adapted to the new model, you might get backdrafting. A proper, qualified heating technician should know how to convert and adapt, and properly install the venting for your new furnace.
Beware the Orphaned Water Heater
When replacing your old furnace with a higher efficiency one, you have to be careful to not leave the water heater using the chimney all by itself – that’s what is called an orphaned water heater, according to Gromicko.
The chimney was designed for the larger amount of flue gases, from your furnace and water heater combined. According to Larry D. Armanda, Owner of Therma-View Infrared and Energy Consultants, orphan water heater-related backdrafting occurs “when the draft temperature is so low in the water heater that it often can’t overcome the slug of cold air inside the chimney, and the flue gasses can't escape so they come back into the CAZ (combustion appliance zone).”
When replacing your furnace with a higher efficient model, makes sure to ask your technician about flue gases from your gas water heater. A reliable company will be able to reroute your gas water heater flue as well to avoid backdrafting.
Use Exhaust Fans
With homes today being sealed so tight, backdrafting can happen when you are actually trying to pull stale, smoky or moist air out of your home. Using your bathroom exhaust fans, kitchen range hoods, dryer vents, attic fans – basically anything that pulls air out of the house – can cause backdrafting through the chimney.
If you have all your windows closed and shut tight, your home becomes completely sealed – except for your chimney. If the water heater comes on, the replacement air will come from the easiest and closest hole in the building, which is usually the chimney.
What can a qualified home inspector do to test for backdrafting?
When Nick Gromico goes into a home, there are several tests he does to see if your home can be backdrafting dangerous toxins and emissions. You as the homeowner will not be able to smell or see these kinds of situations, so it is imperative to get a professional out to your home to do these tests:
- An inspector can use a smoke pencil, or chemical puffer to release a smoke into the draft diverter to see if it gets sucked into the duct (as it should) or if it spills back into the room.
- An inspector can see if there is sufficient draft to pull the flame in the direction of the flue, in your gas-heater by holding a lighter beside the draft diverter.
- Look for a dark residue on the top of your water heater. Sometimes combustion gases that backdraft into a house leave soot.
- A carbon monoxide analyzer can be used to test for backdrafting of that gas. Inspectors should be properly trained to use these before they attempt to use one during an actual inspection, primarily to avoid false negatives.
Bio: Ted Ballantine is a journalist who covers health, retirement and senior care. In his free time, he writes about indoor air quality and respiratory health on his blog.
/ These columns are the work of our guest bloggers who want to share their expert green opinions on a range of topics.