Roof Termination Chimneys
Reference data and engineering information about roof termination chimneys for combustion applications.
Overview
Engineering reference data for Roof Termination Chimneys in combustion engineering.
Key Formulas
Heat Release
Fuel energy release rate.
Air-Fuel Ratio
Mass of air per mass of fuel.
Excess Air
From flue gas oxygen measurement.
Variables
| Symbol | Description | Unit |
|---|---|---|
| Heat release rate | W | |
| Mass flow rate | kg/s | |
| Heating value | J/kg | |
| Air-fuel ratio | — |
Practical Considerations
When designing or specifying roof terminations for chimneys and single-wall vents, several factors influence performance and compliance:
Draft and Performance: The termination height and profile affect the natural draft of the chimney. A poorly chosen termination can reduce draft efficiency, leading to poor appliance performance or smoke spillage.
Weather Protection: While "no caps" are specified in this context, the termination must still be designed to minimize rain, snow, and debris ingress without significantly impeding exhaust flow. Specific designs may use spark arrestors or anti-downdraft features.
Material Compatibility: The termination material must be compatible with the flue gas chemistry and temperature to prevent corrosion or premature failure. Common materials include stainless steel, aluminum, and galvanized steel.
Clearance to Combustibles: Maintain required clearances between the vent termination and any combustible building materials, as specified by the National Fuel Gas Code (NFPA 54) or local building codes.