Which furnace vent is intake?

Author: Jovan Rempel III  |  Last update: Sunday, May 11, 2025

Walking around your house, you might notice a hooded opening along the side. This is your fresh air intake vent, and it's crucial for the optimal performance of your HVAC equipment. In particular, your heating oil furnace depends on this vent to receive air. Newer systems may have more than one vent.

Which is intake and exhaust on furnace?

The exhaust pipe points up while the intake pipe points down.

How do I know if my vent is intake or exhaust?

Fresh Air Intake: If there's a screen, it's an intake. This is where the cool fresh air makes it's way back to your HVAC equipment. You can test this by turning on the furnace and feeling the suction as it draws air in. Exhausts: If the vent has a flap, it's an exhaust.

Where is my furnace intake vent?

Oftentimes, the intake is on the side of the house. It can be in the form of a hood on an exterior wall. Look for a gray vent hood or a white or black plastic PVC pipe. The fresh air intake leads to a duct that draws air into a vent near the furnace.

Why does my furnace have two vents?

Most central air heating and cooling systems have 2 intake vents that help circulate your home's air and clean out any debris by running it through an air filter.

High Efficiency Furnace Venting [Building the Exhaust Port and Air Intake]

What are the two vents on my furnace?

Your home's HVAC system has two kinds of vents: return and supply air vents. These HVAC vents help regulate the air temperature and humidity in your home. They also contribute to air quality and energy efficiency. They just do it in different ways.

What happens if there is improper venting of the furnace?

Your furnace keeps your home cozy during frigid winter temperatures, but could a faulty unit present a major safety hazard for your family? Yes! Furnaces that don't vent adequately send carbon monoxide into the home and increase the risk of house fires.

What happens if the furnace air intake is blocked?

If the intake pipe becomes blocked, the heating system will likely stall and turn off as it can't pull in the required air for the combustion process. If the exhaust pipe becomes blocked, a safety mechanism should trip to prevent dangerous fumes from entering your home.

How to identify supply and return ducts?

A return vent is the opposite of a supply vent. Return vents draw air into the system in order to condition it and pump it back out into the home through the supply vents. To identify a return vent, take a piece of paper and hold it up to the vent. If the paper is drawn towards the vent, then it's a return vent.

What is an intake vent?

What Are Intake Vents? Air intake vents are used to allow outside air to enter into attics and ventilation spaces. Intake vents should be located along a roof assembly's lowest eaves at or near soffits. Intake vents are best used with exhaust vents that are located at or near a roof assembly's peak.

Do all furnaces have fresh air intake?

Every home is legally required to have a fresh air intake if a gas appliance, such as a furnace, is installed.

What does a return air vent look like?

You can usually spot return vents on your walls, ceiling, or floors. Look for a white grille without shutters to spot an air return vent. These vents will typically integrate seamlessly into your home.

How do I know which valve is intake and exhaust?

If you are thinking how you can distinguish the intake from the exhaust valve, then they can most easily be differentiated by the diameter of the valve head. The intake valves have a larger diameter of the valve head, so they are larger.

How do I find my furnace exhaust?

1 - Look at your furnace and find the plastic (pvc) intake and exhaust pipes. Follow them to see where they exit the building; it's most likely through a wall near the furnace. 2 - Go outside and look for the intake and exhaust pipes, based on where they exited the building when you looked at the furnace.

What are the two pipes coming out of my furnace?

If your furnace is 90% efficient or greater, you probably have PVC pipes coming out of the wall of your home that look something like those pictured here. These pipes allow the furnace to intake fresh air and to safely vent flue gasses out of the home.

How to tell the difference between vent and return?

In a supply vent, the air flows out of the ductwork. In a return vent, the air flows into the ductwork. A second difference is the size of the vents. In most situations, the return vent will be much larger than the supply vent.

Which side is supply and return?

Place your hand near the vent while the HVAC system is running. If you feel air blowing out, it's a supply vent. If air is being pulled in, it's a return vent. Supply vents are generally smaller and may have adjustable louvers to control the direction and volume of airflow.

Which duct is the return duct?

Return air ducts channel air from rooms back to the air handler. They're connected to the air grilles you might find on the walls or ceilings of your hallways and larger rooms. The return ducts help maintain good air circulation, preventing hot and cold spots, and keeping your rooms from feeling stuffy.

How come my furnace is blowing cold air?

Your furnace will blow cold air if there is no air to heat and send back into your home. Another reason you may not be getting enough air flow is if your ductwork is not sized properly. Unfortunately, this is quite common. If your return ductwork is too small, it will not be able to take in the required amount of air.

How do you tell if your furnace is venting properly?

Condensation/Moisture: Another sign that your furnace isn't venting properly is noticing condensation or moisture on your windows, especially in the morning when you turn on the furnace. It is caused by the fumes leaking into your home from the furnace.

What happens if the furnace intake is blocked?

If the furnace intake pipe becomes blocked with snow, the heating system can stall because it cannot pull the required oxygen to properly operate. Once the intake pipe becomes blocked, the only way to get the furnace working again is to clear the snow.

Should furnace exhaust be higher than intake?

It's important for the exhaust gas to not get sucked back into the furnace, so manufacturers will usually give several ways to do this. One way is to make the exhaust terminate higher than the intake, usually by at least one foot.

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