Yes, you should absolutely close your chimney flue (damper) during the summer. Leaving it open allows your cooled, air-conditioned air to escape, pulls hot, humid outdoor air into your home, and lets pests or debris inside.
You may have heard stories from relatives and friends when you were growing up that a fireplace's damper needs to remain open in the summer to let your fireplace “air out.” The truth is your fireplace needs to stay shut when it's not used in the summer. Even if your chimney has a cap, it can become damaged.
The "Seven Times Rule" is: The flow area of the largest common vent or chimney shall not exceed seven times the area of the smallest draft hood outlet. NOTE: there are significant differences between the operation of interior and exterior chimneys.
Close the Flue When the Fireplace is Not in Use
In the cold months warm air has an easy exit from the home through that opening. The same is true for cold air in the summertime, when you're probably far from thinking about winter nights by the fire. And do not worry about locking out Santa Claus.
For a Hotter Fire
Fully open the damper to maximize airflow. It provides ample oxygen to the fire, resulting in a more intense and hotter burn. The damper must be fully open when lighting the fire.
How to Do It: Wait until all embers have extinguished and the fireplace is no longer warm to the touch. Closing the damper too soon can trap smoke and carbon monoxide inside your home, creating a dangerous situation. Safety Tip: Always double-check that the fire is completely out before closing the damper.
In the burning process, wood starts to chemically break down at 500oF, producing volatile gases including creosote. These gases burn at about 1100'F; if that temperature is not roached, the gases will escape up the chimney, resulting in the loss of much of the wood's energy.
If the chimney flue is left open after the fire goes out, all the heat generated will escape. Closing the flue will keep the heat inside; you must be careful not to close it too quickly, otherwise you may trap smoke and carbon monoxide in your home. It's best to keep the flue closed when the fireplace is not in use.
This chimney construction rule says: The chimney needs to extend at least 3 feet above the roof on the side of the chimney where the roof is highest. The top of the chimney must be at least 2 feet higher than any part of the roof or any component on the roof that's within 10 feet of it.
The majority of heat loss in a house escapes through air leaks and drafts (around 35% to 38%) and poorly insulated walls (around 35%). Because warm air naturally rises, the attic and roof are also massive culprits, accounting for about 25% of total heat loss.
Mice aren't only found in the attic or kitchen. They can also make their way down your chimney. Mice are mainly attracted to open spaces and warmth, so your chimney is the perfect place to nest. Leaving them unattended could lead to a full-on infestation in your home and costly repairs.
Professional roofers possess extensive experience with chimney-related repairs that directly impact roof integrity and weatherproofing systems. Their expertise covers external chimney components including flashing replacement, crown repairs, and addressing problematic areas where the chimney penetrates the roofline.
The building code requires that the top of the chimney extends not less than 1 m (3 ft.) above the point it exits the roof and 600 mm (2 ft.) higher than any roof, building or other obstacle within a horizontal distance of 3m (10 ft.).
Tip #1 – Close The Fireplace Damper Or Use A Damper Seal A fireplace flue damper enables you to control how much air flows up your home's chimney when the fireplace is in use. Adjusting the damper allows you to burn a fire efficiently and safely.
Clay tile liners and cast-in-place liners typically last around 50 years. Stainless steel flue liners generally last for 15 to 20 years (though low quality liners may not even last for five). Good quality stainless steel chimney liners often come with a lifetime warranty.
Your flue (via the damper) should be adjusted based on whether your fireplace is in use: Open the flue before starting a fire. This allows proper ventilation so smoke, fumes, and combustion gases escape up the chimney instead of entering your home. Leave it fully open while the fire is burning.
It takes time for your home to warm up and cool down. If you're not sure how long it takes, try turning the heating on about 30 minutes before you need it. You should turn it off 30 minutes before you'll stop needing it.
It typically takes an air conditioner about 30 to 60 minutes to cool a house by 1 degree Fahrenheit. However, this timeframe is highly variable and depends on outdoor weather, humidity levels, and how well your home is insulated.
Actual percentages of heat loss for each:
Additionally, in the early 1980's, tests were conducted to discover which kind of wood created the most creosote in a regular “open” fireplace. The results were surprising. Contrary to popular opinion, the hardwood's, like oak and poplar, created more creosote than the softwoods, like tamarack and pine.
At this point we cover everything in the rule: the chimney is a minimum for 3' above the uphill side of the roof and 2' higher than anything within 10' feet. This clearance is set up to help prevent any embers from landing on the roof. This height requirement is extremely important for the safety of the chimney system.
The biggest mistake? Using logs that simply aren't dry enough. Firewood with high moisture content produces more smoke, less heat and leaves behind sticky tar (creosote) in your flue and burner. It also makes lighting your fire harder, wastes energy and can even damage your stove.
Close the Flue When the Fireplace is Not in Use
In the cold months warm air has an easy exit from the home through that opening. The same is true for cold air in the summertime, when you're probably far from thinking about winter nights by the fire. And do not worry about locking out Santa Claus.
A fully open damper allows maximum airflow, making the fire burn hotter and faster. If you want a slower burn or a fire that lasts longer, you can partially close the damper to reduce the oxygen supply. Just be careful not to close it too much because it can lead to poor combustion and smoke buildup.