Furnace Vent Codes: What You Need to Know

When you discover a furnace with ducts that are exposed to outside air, you may wonder if there are local codes regarding indoor-outdoor air. There are codes regarding the operation of chimney-connected furnaces and their exhaust ducts. And while they may not be as visible as the walls, ceilings, or windows in a home, it’s important to remember that the various components of your home – including those related to the structure and utilities within it – need to meet particular standards for safety, efficiency and durability if you want your home to last for years to come. With so many different codes out there, how do you know which one applies to your situation? This article will provide an overview of some of the most common local code requirements related to furnaces and their venting systems.

Chimney-connected Furnace Venting Basics

The National Fire Protection Association (NFPA) defines a chimney-connected furnace as, “one that is connected to a masonry or factory-built chimney flue by an insulated connector.” We’ll take a look at some of the most common types of furnaces that meet this description below. – Direct-vent and non-ducted systems – Direct-vent and non-ducted combination systems – Direct-vent and non-ducted systems with a single-path filter – Standard-vent systems The code requirements for each of these systems differ in terms of how they’re vented. In other words, they each use a different path to get exhausted gases outside the home.

Which Codes Apply to My Furnace?

As we briefly discussed above, different types of furnaces with different types of exhaust ducting will be subject to different code requirements. To determine which codes apply to your furnace’s setup, you’ll need to know the type of furnace you have and how the exhaust ducts are arranged. Before we go any further, it’s important to note that any alteration to your existing ductwork or furnace may require additional permits or inspections. This is particularly true if you’re making changes to an existing chimney, making significant modifications to your home’s structure, or adding new systems.

Determining Exhaust Duct Location and Size

Exhaust duct location requirements vary by code. If you’re adding an exhaust duct to an existing furnace, or if the existing ductwork is not sufficient to provide proper ventilation, you should locate the duct as far away from the living space as possible. This minimizes the risk of indoor air contamination from the outdoor air. – If your existing chimney is not tall enough to meet code requirements, you may need to consider other options, such as locating the exhaust duct outdoors and connecting it to the chimney. – For ductwork that is located indoors, the duct should be as short as possible and located away from doors, windows, and air intakes. – The exhaust duct should be as straight as possible, and it should use the most direct path to the exterior of the home. – If the exhaust duct runs through unheated areas of your home, such as crawlspaces, attics, or unfinished basements, it should be insulated to prevent heat loss. – The minimum diameters for residential exhaust ducts are as follows: – Round ducts – 6 inches – Square ducts – 8 inches – Rectangular ducts – 8 inches – Circular ducts – 12 inches

Requirements for Outlet Ducts

The requirements for outlet ducts are different between direct-vent systems and standard-vent systems. With a direct-vent system, the exhaust duct is usually run through the interior wall of the home and connected to an exterior wall via a wall connector. With a standard-vent system, the exhaust duct is usually run through an exterior wall and connected to the exterior wall via an exhaust connector. For both types of systems, the outlet duct should be as short as possible and located as far away from doors, windows, and air intakes as possible.

Requirements for Supply Ducts

Requirements for supply ducts are generally the same for direct-vent and standard-vent systems, as well as for single-path filter systems. For these systems, the supply duct should be as short as possible and located as far away from doors, windows, and air intakes as possible. Additionally, the supply duct should be as straight as possible, and it should use the most direct path to the supply source.

Summing Up

This article has provided an overview of some of the most common local code requirements related to furnaces and their venting systems. If you’re planning to install or replace a furnace, you’ll want to keep in mind that these various codes are designed to protect both the homeowners and the people who service and repair the systems. For instance, it’s important to keep the various components of your home – including the furnace, exhaust ducts, and intake vents – located as far away from doors, windows, and air intakes as possible to minimize the risk of indoor air contamination. These requirements are also in place to help the people who work on these systems be safe by providing adequate space and clearances between the various components of the system and themselves.