Why Does My Fireplace Backdraft? - Kansas City Chimney Repair

Think of your house and chimney system as a living, breathing thing. They actually need to breathe to exchange the stale, stagnant air for fresh air. There are many appliances pushing air out of your house—bathroom fans, central vacuums, range hoods, clothes dryers, etc.—leaving it constantly searching for ways to bring new air back in to replace it. This creates negative pressure in your house (meaning your house becomes more interested in trying to suck air in than push air out). This most definitely interferes with the air supply for your entire chimney system and can become even more obvious for those homeowners who have basement fireplaces.

chimney back draft & repair in Overland Park KS

When full of hot air, your chimney pulls air through the firebox; this pulling action is what’s referred to as draft. The simplest way to increase the draft in your chimney is to burn a hotter fire—the hotter the air gets, the lighter it becomes, thereby providing it with more pull. This increased pull draws more air through the firebox and up your chimney. The tendency of warm house air to rise results in pressure differences at various levels in the house. The pressure in the basement and lower levels of your house will be less than the atmospheric pressure. In upper levels of your house, the pressure will be higher than the atmospheric pressure as the rising air pushes against the ceiling. At some point between these high and low pressure zones is an area where the pressure is neutral; this point is known as the neutral pressure plane.

The difference in pressures creates what is called the stack effect. A taller house will have a greater stack effect than a shorter house. The stack effect in your house can make a considerable difference in the venting and performance of your fuel burning appliances—wood burning, oil and gas fired appliances. Basements are the most susceptible to problems caused by the stack effect, as it’s the lowest point in the home. Appliances and chimney openings located below the neutral pressure plane of the house must work against the negative pressure induced by the stack effect. One problem often created by this struggle is what is commonly referred to as a backdraft.

If a backdraft forms when you’re trying to light a fire, it may be because the fire simply isn’t hot enough yet. To correct this, ignite some fast-burning wood or paper. If you live in a particularly windy location, you may have problems with wind blowing downward through the chimney. Installing a wind-resistant chimney cap should prevent this from happening. Finally, you should avoid blowing hot air out of the room with the fireplace via exhaust fans while a fire is burning. If the fire doesn’t get the air it needs, it will burn cooler, eventually causing it to smolder and fill the room with smoke.

Many things can cause your draft to become compromised: chimney blockages, closed and/or clogged dampers, improper or inefficient construction, lower-temperature fires, or structural damage. Fluesbrothers Chimney Service understands that the safety of your family includes protecting them from any potential danger from fire and illnesses caused by not keeping your chimney appliance in top working condition. One of our CSIA-certified chimney sweeps can evaluate your chimney and recommend any corrective action to ensure that it is capable of the proper draft and flow. Call us today or click here to schedule your appointment online!