Venting a furnace properly involves safely removing combustion gases from your home. Proper furnace venting depends on the type of furnace you have, but generally involves creating an airtight pathway for exhaust gases to exit your home through either the roof or a sidewall.
Understanding Furnace Venting
The method for venting a furnace varies depending on the type of furnace you have and local building codes. Here's a breakdown of common methods:
- Natural Draft Furnaces: These older, less efficient furnaces rely on the natural buoyancy of hot gases to rise through the vent pipe (typically a chimney). Proper venting requires ensuring the chimney is clear and in good condition, and that the vent connector from the furnace to the chimney has the correct slope and size.
- Forced Draft Furnaces (Mid-Efficiency): These furnaces use a fan to assist in pushing exhaust gases. They often use a B-vent, a double-walled metal pipe, to vent through the roof.
- High-Efficiency Condensing Furnaces: These furnaces extract more heat from the exhaust gases, causing water vapor to condense. This condensate can be acidic, so they require special venting materials, such as PVC or CPVC pipe, to resist corrosion. These are typically vented through a sidewall.
Steps for Sidewall Venting (High-Efficiency Furnaces):
Disclaimer: This is a general overview. Always consult the furnace manufacturer's instructions and local building codes for specific requirements. Working with gas appliances can be dangerous, so consider hiring a qualified HVAC technician.
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Planning the Vent Route: Determine the shortest and most direct route to an exterior wall. Consider proximity to windows, doors, and air intakes, as exhaust gases should not be drawn back into the home. Check local codes for required clearances.
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Creating the Opening: Drill a hole through the exterior wall large enough to accommodate the vent pipe and any necessary fittings.
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Installing the Vent Pipe:
- Connect the PVC or CPVC vent pipe to the furnace's vent outlet.
- Run the pipe through the hole in the wall.
- Use appropriate fittings (elbows, couplings) to create a secure and airtight connection.
- Ensure the pipe slopes slightly downwards towards the furnace to allow condensate to drain back into the unit.
- Proper sidewall venting often 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.
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Sealing and Supporting the Vent Pipe:
- Seal the gap around the vent pipe where it passes through the wall with weatherproof sealant.
- Use pipe supports to secure the vent pipe along its route and prevent sagging.
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Installing the Vent Termination:
- Install a vent termination cap on the outside of the wall to prevent rain, snow, and debris from entering the vent pipe. The termination should also be designed to prevent back drafting.
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Testing: After installation, test the venting system for leaks using a combustion analyzer. This will ensure that the furnace is venting properly and that no combustion gases are leaking into the home.
Important Considerations:
- Material Compatibility: Always use venting materials that are approved for use with your type of furnace. Using the wrong materials can lead to corrosion, leaks, and dangerous carbon monoxide buildup.
- Proper Sizing: The vent pipe must be the correct size for the furnace's BTU input. Consult the furnace manufacturer's specifications for sizing requirements.
- Local Codes: Adhere to all local building codes and regulations regarding furnace venting. These codes are in place to protect your safety and the safety of others.
- Carbon Monoxide Detectors: Install carbon monoxide detectors on every level of your home, especially near sleeping areas. Test them regularly to ensure they are working properly.
- Professional Installation: If you are not comfortable working with gas appliances, hire a qualified HVAC technician to install or repair your furnace venting system. This is the safest way to ensure the job is done correctly.
Summary
Proper furnace venting is critical for safety and efficiency. Understanding the type of furnace you have and following the appropriate venting procedures is essential. When in doubt, consult a qualified HVAC technician.
