Do You Need A Chimney For A Gas Furnace?

by | Last updated on January 24, 2024

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Do you need a chimney for a gas furnace? But while most homeowners are aware of the need to have their fireplace or woodstove chimneys cleaned and inspected, many don’t realize that a gas heating appliance – be it a furnace, boiler, or even a hot water heater – also

relies on a chimney for proper venting of the exhaust

.

Contents hide

Can you vent a furnace without a chimney?


Two or more appliances could vent into an exterior chimney, but design conditions must be appropriate along with appliance fuel input

. Additionally, one of the appliances must have a draft diverter (natural draft system). Interior chimneys typically benefit from the heat of the structure.

Does a gas furnace need a chimney liner?

Draft & Efficiency

When it comes down to it, you need your furnace functioning as efficiently as possible to ensure you get the warmth and comfort you need this winter.

Liners can help direct gases up and out of your flue, so your system works better and faces less decay and deterioration

.

Does a gas furnace need to be vented?

Is the chimney connected to the furnace?

In houses with wood-burning fireplaces, a masonry chimney will usually contain two separate paths upward to the roof: a flue for the fireplace and one for the furnace.

In the basement, the furnace connects to the chimney through a metal duct

and the exhaust gases come out at the top of the chimney above the roof.

Do modern furnaces need a chimney?

But while most homeowners are aware of the need to have their fireplace or woodstove chimneys cleaned and inspected, many don’t realize that a gas heating appliance – be it a furnace, boiler, or even a hot water heater – also

relies on a chimney for proper venting of the exhaust

.

Can you vent a gas furnace through a wall?

Direct Vents


These furnace vents can be installed horizontally through an exterior wall

, or vertically so exhaust fumes go out through the roof. Although more costly than a natural vent, a direct vent is also a more efficient and safer option.

Do I need a chimney liner for a 80 gas furnace?


Older, less efficient furnaces do not need a chimney liner

. This is because the steam they release can be up to 700 degrees Fahrenheit. That means that the steam uses the entire space of the chimney as it travels outwards. More efficient furnaces, such as those at 80% AFUE, use the chimney for ventilation as well.

What is the use of chimney in furnace?

A chimney is an architectural ventilation structure made of masonry, clay or metal that

isolates hot toxic exhaust gases or smoke

produced by a boiler, stove, furnace, incinerator or fireplace from human living areas.

Does chimney need to be lined for gas fireplace?

Whether you go from gas to wood burning or vice versa,

you must install a new chimney liner appropriate for that type of fuel and use

. The same rule applies to heating and hot water equipment because different materials are more suited for different types of fuel.

Where do gas furnaces vent?

Old furnaces tend to be furnaces with standard-efficiency ratings. These furnaces vent gas

away from your house through a flue pipe

. The flue pipe is attached to the heat exchanger, where the gas combusts and produces heat energy. Gas exits the house through the exhaust pipe, which usually leads up to a house’s roof.

How do you vent a gas furnace?

Can a furnace be in a closed room?

Does a furnace room need ventilation? Most new building codes require that spaces that house gas-fired appliances such as water heaters and furnaces have an outside ventilation source to provide combustion air.

Electric Furnaces or water heaters do not need ventilation to support combustion

.

What is code for furnace exhaust?

503.6.


A Type B or L gas vent shall terminate not less than 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar

. A Type B-W gas vent shall terminate not less than 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.

How often should you clean your gas furnace chimney?

The National Fire Protection Assoc. 211 codes state that “chimneys must be inspected and cleaned

if needed annually

” – just like the oil service man services the furnace annually, so should the chimney system be serviced annually.

How do I vent my furnace to the roof?

Do high efficiency furnaces use chimney?

Higher efficiency furnaces do not let out steam that is so high in temperature.

A really high efficiency unit (90% and above) does not even use the chimney

! They have their own plastic pipes that leave the home from the side of the house because the steam is only about 150 degrees.

Why is a metal vent often preferred rather than a masonry chimney?

Why is a metal vent often preferred rather than a masonry chimney?

Metal vents reach operating temperatures quicker than masonry vents do

. Masonry chimneys tend to cool the flue gases.

Can you install a high efficiency furnace with only one pipe?

Can a gas furnace be vented out the side of the house?


An 80% efficient furnace CAN be side wall vented per National Fuel as Code 7.3. 4 with the use of a “mechanical draft system of either forced or induced draft design”

.

How far can you run a furnace exhaust?

The maximum vertical distance you can run a furnace exhaust vent is about

15 feet

. If there is a forced air inlet within 10 feet of the exhaust vent, the exhaust gas ventilation terminal should be positioned at least 3 feet above it.

How do you vent a high efficiency furnace through a wall?

Proper sidewall venting requires

installing separate vent pipes horizontally so that they vent to the outdoors through a wall of your home

. These ventilation pipes should be isolated from the furnace combustion chamber and made airtight to eliminate the possibility of combustion gas leakage.

Is chimney lining necessary?

How much does a chimney liner cost?

A chimney liner cost averages

$625 to $7,000

, with a national average of $2,500. Chimney relining costs are primarily based on the type of material you choose to install, the size of the chimney, the roof pitch, the chimney’s condition, labor, and permits.

Do you have to line your chimney?

When an installer checks your chimney they may find that

the only way to provide you with a compliant and safe installation is to line the chimney

. If there is any risk that the chimney could leak fumes in to the house they must line it with a suitable re-lining material.

When did houses stop having chimneys?

Chimneys are most common in homes built

before 1900

, while fireplaces experienced a bump in popularity in the 1980s, 1990s and 2000s. Not all fireplaces need a chimney.

What is the need of a chimney in the house?

The primary function of the chimney is

to direct the smoke away from the stove and out of the house

. However, this is not the only function of the stove, as it must also: Ensure that enough air is drawn into the stove for the fire to burn clean.

What is the difference between chimney and stack?

When you think of a chimney, you may picture the brick structure on top of a roof, but that is actually known as the “stack”.

The chimney stack is the part that is above the roofline

.

Is an unlined chimney safe?

Why does a gas fireplace need a chimney?

Does a gas furnace have an exhaust?


One of the most important parts of a gas-powered furnace is the exhaust flue

. Although this component plays a largely passive role in furnace operation, your system simply couldn’t work without it. If you would like to improve your knowledge of residential HVAC systems, keep reading.

How are new furnaces vented?

Can you vent a gas furnace with PVC pipe?

How safe are natural gas furnaces?


Gas Heaters Are Safe to Use

The main concern with a gas heater is the leak of carbon monoxide, which is a toxic byproduct of the combustion of gas. Furnaces vent out CO through a flue, and there is very little chance that it will flow into the house.

Can you enclose a gas furnace?

Can a Furnace be Enclosed?

Yes, you can enclose your furnace

. However, and according to this information for the US Department of Energy, you do want to make sure that any combustion furnaces have chimneys that satisfy all manufacturers ‘ recommendations and local building codes.

Can a gas furnace be in a closet?


No, you can’t install a furnace in a bedroom closet

— or the bedroom for that matter. The major component of the average furnace’s operation is its burners. A furnace generates heat thanks to fire from a gas or propane energy source.

David Martineau
Author
David Martineau
David is an interior designer and home improvement expert. With a degree in architecture, David has worked on various renovation projects and has written for several home and garden publications. David's expertise in decorating, renovation, and repair will help you create your dream home.