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What Is InnoFlue® Lite? A Guide to Cost-Effective Flue Gas Venting

When it comes to flue gas venting, selecting the right system is essential, not just for performance, but for safety, compliance, and long-term reliability. Whether you're installing a direct vent water heater, upgrading a boiler, or reviewing gas hot water heater venting requirements, choosing the right vent material can significantly impact both cost and performance. 

For many installations, particularly in non-code or non UL 1738 enforced markets, InnoFlue® Lite offers a cost-effective solution designed for high-efficiency appliances.

Here we’ll cover: 

  • What InnoFlue® Lite is 
  • How it compares to standard InnoFlue® 
  • How UL 1738 and ULC S636 impacts pipe selection
  • The best way to vent a boiler (including air intake considerations) 
Exterior side wall of a white metal building with two vertical vent pipes mounted to the siding, under a cloudy sky with trees and power lines in the background.

What Is InnoFlue® Lite?

InnoFlue® Lite is a polypropylene flue gas venting system designed for use with high-efficiency gas-fired appliances, including: 

  • Boilers 
  • Furnaces 
  • Tankless water heaters 
  • Gas water heaters 

It is specifically engineered for condensing appliances (Category II & IV), which produce lower-temperature exhaust gases and acidic condensate. 

Key Features of InnoFlue® Lite: 

  • Suitable for Category II and IV appliances 
  • Rated for flue gas temperatures up to 230°F (110°C) 
  • Designed for residential applications (commonly 2” and 3” diameters)
  • Lightweight
  • Gasketed system for faster installation
  • Listed to the CE EN 14471

In simple terms:

InnoFlue® Lite is a lightweight, cost-effective polypropylene venting system designed for safely exhausting flue gases from high-efficiency appliances, where UL 1738 listing is not required.

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Why InnoFlue® Lite Matters

Temperature  

  • Modern heating systems, especially condensing boilers, can produce exhaust temperatures that exceed the limits of PVC venting materials. As a result, more heat-resistant alternatives are often required, such as InnoFlue® Lite.

Corrosion

  • Modern heating systems, especially condensing boilers produce acidic condensate
  • Metal venting faces a corrosion risk in condensing appliances
  • InnoFlue® Lite resists acidic condensate corrosion.

InnoFlue® Lite

  • Maintains long-term structural integrity
  • Offers simplified installation

What Is the Difference Between InnoFlue® Lite and InnoFlue®?

The only differences are UL 1738 listing, flame retardancy, and color. All other performance factors are exactly the same. 

InnoFlue® Lite 

  • Not UL 1738 listed
  • Does not include flame-retardant additives required for listing
  • Lower cost alternative
  • Intended for areas or municipalities not yet enforcing UL1738

Standard InnoFlue®

  • UL 1738 listed 
  • Includes required flame-retardant properties
  • Approved for code-compliant installations 

Important Clarification:

Performance characteristics (temperature rating, pressure rating, condensate resistance) are very similar, but code acceptance is the deciding factor. 

  • Use InnoFlue® Lite-where UL 1738 is not required for a cost-effective alternative
  • Use InnoFlue®-where UL 1738 is required by code. InnoFlue® can also be used in non-code markets, but it is not required.

How UL 1738 Impacts Pipe Selection

UL 1738 is the recognized North American standard for special gas vent systems used with positive-pressure, condensing appliances. 


A Summary of what UL 1738 Covers:

  • Temperature resistance 
  • Positive pressure operation 
  • Condensate handling 
  • Flame spread / fire safety 

Why It Matters:

  • Required by many state and local codes 
  • Enforced by inspectors and AHJs (Authorities Having Jurisdiction)
  • Ensures safe venting of combustion gases
Close-up of hands fastening an octoclamp between white and gray pipes using a threaded bolt and nuts.

What Is the Best Way to Vent a Boiler?

Best practices for flue gas venting are based on both code and manufacturer instructions. 

1. Select the Correct Vent Material

  • If UL 1738 is required-use listed systems (e.g., standard InnoFlue®) 
  • If not required-InnoFlue® Lite can be used as a cost-effective alternative

2. Manage Condensate Properly

Condensing appliances produce acidic condensate: 

  • Horizontal runs must be pitched back toward the appliance
  • Condensate must be properly drained and neutralized where required

3. Follow Manufacturer Installation Instructions

This is non-negotiable: 

  • Vent length limits 
  • Fittings 
  • Termination requirements 

Air Intake Considerations

Key Advantage of InnoFlue® Lite:

  • It can be used for air intake applications, including in markets where it is not approved for exhaust. Air intake is not subject to UL 1738 in the same way exhaust venting is, but you should always confirm with local code and appliance manufacturer 

Why This Matters:

  • Improves combustion efficiency
  • Supports balanced systems
  • Reduces indoor air contamination risk
man with white pipe

Is InnoFlue® Lite Right for Your Project?

Choose InnoFlue® Lite if:

  • You need a cost-effective alternative that can also support air intake

Choose Standard InnoFlue® if:

  • Your project requires code compliance / UL 1738 listing

InnoFlue® Lite provides a reliable, cost-effective solution for flue gas venting in applications where UL 1738 listing is not required, while still delivering the performance benefits of standard InnoFlue® polypropylene venting systems. 

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