We frequently hear from homeowners seeking answers to repair and maintenance problems. Many of these questions and answers are compiled in our Home Improvement Library. Here is a recent question.
Question
On certain days, our first floor fireplace causes a smell to backup in the house. It doesn’t matter if the flue is open or closed, or a window in the room is open and a fan going. Do you know why this is happening and what we can do to prevent it?
Answer
We suspect your house has a negative pressure imbalance from either a forced air heating system with leaks in the return air ductwork or exhaust vent fan(s) drawing a vacuum on the house.
To explain the physics of this, imagine all the windows and doors in your house closed and a giant vacuum cleaner hooked up through the wall sucking the air out. Where would the replacement air come into the house from? The “make-up” air would come down the chimney, bringing the smell inside the house.
An imbalanced forced-air ductwork system often creates this negative pressure, and is typically caused by a leaky or undersized return air duct system. Sealing your return air ductwork joints stops air leakage. Also, under-sized return air systems are more the rule than exception; increasing the return air volume is another solution for preventing the fireplace smell.
Other causes for the odor are possible. Consider having a professional chimney sweep clean and inspect the flue to minimize possible creosote buildup in the flue. And sometimes the geography around your house creates a pressure situation where the wind blows down your chimney and brings the smell inside. However, the more common ailment is the imbalanced ductwork system or vent fans.
For help determining the cause and solution for fireplace issues – or even a fireplace facelift – call our office at 314.909.1800 or contact us here.