Can I Install a Furnace Intake Vent? A Step-By-Step Guide

Furnace fresh air intake vents bring in outside air, which is heated and then distributed through ductwork throughout the house. This is needed to replace the stale, stuffy indoor air that exhaust from bathroom fans and dryers brings into homes, and prevent deadly carbon monoxide buildup.

Older homes typically have one fresh air intake vent, while newer buildings, with tighter insulation, tend to have several due to stricter building codes.

How to Install a Furnace Intake Vent

Having fresh air intake vents on your furnace is vital because it allows the furnace to use oxygen that is present in the outdoor air. Without it, the furnace would have to burn indoor oxygen in the combustion process — which isn’t ideal for your home’s indoor air quality.

The first step in preparing for fresh air intake is to install a 6-inch metal galvanized duct line from the collar up to the stub that connects to the intake hood. Screw the duct together and, if needed, use a pipe crimper to fit it. Once the duct is installed, the barometric damper should be placed on top of the intake hood. Make sure the arrows on the damper are pointing toward the furnace to indicate which direction air will flow.

Preparation

Furnaces need fresh air for proper combustion. Without a fresh air intake, the furnace will pump indoor air through the exhaust pipe, pushing out pollutants such as mold spores and decomposition gases that decrease your family’s health.

The air intake vent is a separate port, usually located in the basement, that allows outdoor air to be drawn in through the pipe and into the furnace. It’s essential that it be installed in a space away from exhaust and dryer vents, as these will cause turbulence and recirculation of suffocating gases.

Install a 6-inch galvanized duct from the intake hood collar to the return stub, making sure to screw and fit all joints. Then, install the barometric damper on top of the intake hood and make sure its arrows point at the furnace.

Installing the Intake Hood

A gas furnace needs oxygen to burn. Since the entire house is part of the ventilation system to keep air clean, your home’s gas furnace relies on ducting to get fresh oxygen to its combustion chamber.

The fresh air intake vent is an open duct that runs from the outside vent to a basement or room housing your home’s furnace. Homeowners often instinctively block fresh air intake vents in their homes — and they shouldn’t.

If you block your furnace’s fresh air intake, your home could experience negative pressure that draws carbon monoxide back through your vents and into your living spaces. Additionally, turbulence caused by too many turns in your fresh air venting can cause corrosive exhaust that eats holes in the metal venting pipes of your high-efficiency gas furnace.

Installing the Return Duct

Fresh air must be pumped into conventional furnaces to avoid carbon monoxide and other dangerous combustion gases from building up inside the home. Air that’s contaminated by these harmful substances also damages the heat exchanger and shortens its lifespan.

Often, fresh air intake vents are located in a room that contains the furnace to help make sure this dangerous air doesn’t contaminate the rest of the house. However, homeowners sometimes block these vents by tampering with the ductwork.

To install the return duct, start by drilling a 6-inch hole adjacent to the furnace pipe with a pair of aviation snips. Then, place a metal collar in the hole and screw it down, making sure it is stable before proceeding to the next step. The duct should be made of galvanized material for maximum durability.

Installing the Barometric Damper

Barometric dampers help regulate the draft of your stove. They are installed in the flue pipe and use a mechanism that responds to changes in air pressure to open and close. You will need to test the damper and adjust it periodically to keep it functioning correctly. It is important to clean the damper and keep it free from blockages.

A fresh air intake vents outdoor air into your house to replace conditioned indoor air that is exhausted by the furnace. Homes without an intake vent can create negative pressure that draws in outside air from crawl spaces, attics and unconditioned spaces leading to health problems. If you notice your damper (draft regulator door) is stuck shut, a heating service technician can easily fix it.