How To Vent A Furnace Through A Wall? Essential Guide

Rima Chatterjee

When it comes to furnace installation, venting is essential. Direct venting through a wall is an option for homes without chimneys. Consider clearances and distances to avoid damage or danger. This article will cover all you need to know about sidewall direct venting. Plus, pro tips to help you install.

how to vent a furnace through a wall

Two pipes are needed for direct venting: one for exhaust gases and another for intake air. PVC or metal is used for the pipes. Manufacturer specifications and local code regulations must be followed. Clearances from combustibles, windows, doors, properties, and snow must be taken into account. High-efficiency furnaces may require condensate drains.

Check the location of the combustion air intake inlet. Choose an appropriate position on the sidewall for the vent outlet. Make sure there is enough space for airflow and maintenance access. Install the pipes securely, avoiding sharp bends that could impede exhaust gas flow or cause leaks.

One pro tip is to use a blower fan or an inclined plane. This prevents backdrafts and pipe blockages due to wind gusts or snow. Insulate the pipes where they penetrate exterior walls to minimize heat loss and water vapor condensation.

Playing Tetris with your home’s layout is key to finding the perfect spot for your furnace!

Choosing the Right Location for Your Furnace

Choosing the right spot for your furnace is key. A direct-vent gas furnace needs proper ventilation and air intake from outside

  • Clearance distances for a heating appliance installed against a combustible wall should not be less than 6 inches.
  • Balancing airflow is important to prevent damage. 
  • Use a floor drain or slanted pipe to prevent water accumulation. 
  • PVC pipes must only be used for high-efficiency furnaces & boilers
  • Check for leaks or damages in the propane or natural gas furnaces.

A cautionary tale: homeowners installed a new furnace without following specs. Result? Poor efficiency and icicles on the neighbor’s fence! Don’t worry, we’re here to help you with direct vent and exhaust systems.

Understanding Direct Vent and Exhaust Systems

Direct vent and exhaust systems are important for the proper functioning of furnaces and heaters. These systems can be dangerous if not installed correctly, as they expel poisonous gases like carbon monoxide. Here is some info about them:

Direct VentingOne pipe takes in fresh air from outside and lets out exhaust gases.
Sidewall VentingAir and gases come in and out of the same wall.
Power VentingElectricity or a fan pushes gases out of the home, and another device controls the airflow.

It’s essential to remember the specifics of each system. Clearances, material distances, snow levels, wind direction, intake terminations, and pipe locations all matter.

My neighbor had a propane fireplace that was improperly drafted. Too much water vapor went into the crawl space, building up icicles. They noticed the humidity and wetness and fixed it before it became more hazardous. Ignoring clearances can lead to serious trouble like a fire-breathing furnace!

Understanding Clearances and Distance Requirements

Clearances and distance requirements are important to remember when venting a furnace through a wall. Not following these specs could cause property damage or even deadly carbon monoxide gas leaking into the house. To stay safe and efficient, it’s essential to understand these clearances and distances.

We need to take a look at the clearance distances. The table below shows the minimum space between direct exhaust vents and air intake terminals based on the equipment type and the vent system used. These clearances are vital for proper airflow, preventing snow, water vapor condensation, and potentially combustible material hazards.

Equipment TypeVent System UsedClearance Distances(Feet)
Gas FurnaceDirect exhaust1 foot above grade
Sidewall2 feet from the property line
Power vent4 feet from any opening like doors, windows, etc.
Gas BoilerDirect exhaust1 foot above grade
Sidewall2 feet horizontally from any opening like doors, windows
Furnace Heat ExchangerDirect exhaust3 feet horizontally or >5 feet vertically from the property line
Power vent Gas AppliancePVC pipesPer manufacturer instructions

Apart from these clearances, the vent pipe’s position concerning upwind structures such as fences and neighboring houses must also be considered. Be sure to meet local building code standards for safety.

High-efficiency furnaces have the advantage of using plastic PVC pipes instead of metal flue pipes. However, plastic pipes may be a concern for heat resistance with regard to low-temperature condensate drains. Thermo Products or Weil-McLain should be read before installing a high-efficiency furnace venting system.

Installing the Venting System

When it comes to installing a furnace venting system, there are a few important things to consider. Direct vent, gas furnaces are popular for their efficiency and easy installation. However, it must be done correctly for safe operation.

  1. Location: Find a suitable exterior wall or sidewall to install the venting system and ensure it meets manufacturer specifications and local building codes.
  2. Vent Pipes: PVC pipes or metal vents are usually used for high-efficiency furnaces. They provide proper airflow and ventilation while avoiding leaks.
  3. Installation & Security: Secure the venting system as per manufacturer instructions. Make sure the air intake terminations are positioned upwind of obstructions like doors or fences.

It’s essential to read the installation manual carefully and seek professional advice if necessary. Carbon monoxide poisoning can occur if condensation builds up due to improper terminal positioning or blockage from snow accumulation.

Venting problems stressing you out? Let’s sort it out!

Troubleshooting Common Venting Problems

Having issues with your furnace’s venting can be annoying. Check the manufacturer’s installation manual and follow the proper distances for vent systems. Clear the combustion air intake inlet from any blockage to ensure proper fuel combustion. Position the vent outlet upwind of any doors, fences, or windows to stop snow accumulation or wind damage.

Hire a certified HVAC technician to repair and maintain your heating gear. Install CO detectors on each level of the house. states that “Fatal carbon monoxide poisoning occurred in a nearby home due to condensate drain spilling water outside that formed icicles and backed up exhaust gases into their propane fireplace.” 

Be thorough when reading your furnace installation manual or Heating and Ventilating Contractors Association website data to stay safe.

If you’re scared of high-efficiency furnaces and their venting, you’re not alone.

Understanding High-Efficiency Furnaces and Their Venting Requirements

High-efficiency furnaces are becoming popular for their ability to heat homes more efficiently. But, proper venting is a must. Direct vent systems are great for gas-fired appliances as they require less clearance than traditional flue systems.

When installing a high-efficiency furnace, be sure to follow the manufacturer’s instructions. The placement of the furnace vent outlet and air intake must be correct. Clearances should be observed too, so that combustible materials do not touch the vent system.

You can use PVC pipes as a material for furnace venting. Just make sure that it meets the requirements outlined in codes and regulations.

A homeowner once noticed icicles forming on their new furnace’s exhaust venting during winter. It was due to improper location and installation. We fixed the issue by correctly positioning the furnace and taking other necessary steps, enabling safe furnace operations all year.

To vent your high-efficiency furnace safely and efficiently, follow these tips:

  • Use direct vent systems for gas-fired appliances.
  • Follow manufacturer instructions for proper placement of the vent outlet and air intake.
  • Observe clearances to prevent combustible materials from touching the vent system.
  • Use PVC pipes for furnace venting if it meets code and regulation requirements.


Venting a furnace through a wall is important for its efficiency and safety. Keep the correct clearance distance and follow instructions to stop damage and carbon monoxide gas leaks. PVC pipes are best for high-efficiency furnaces for exhaust and air intake. Position the vent terminal away from windows, doors, and combustible materials. Check manufacturer specifications and local gas codes when installing new furnaces. High-efficiency furnaces with condensate drain lines must terminate in a floor drain or an approved discharge location according to local codes. Attaching them directly to a roof fan can cause damage due to ice buildup.

About the author

Debarghya Roy: A heating systems author, Passionate about energy efficiency and sustainability, Sharing insights and empowering readers through informative blog articles.