The stack effect in plain terms

Warm air is lighter than cold air. In a multi-story building during a Denver winter, heated air inside tends to rise and push out through the upper floors, while cold air is drawn in low. The result is a slow, building-wide upward flow, strongest on cold, still days. Smoke from a lower unit rides that flow up through shafts, stairwells and the gaps around pipes and wiring.

Cherry Creek North and the blocks around the shopping district have many mid-rise condo buildings with stacked units, shared plumbing walls and vertical shafts for vents and trash chutes. Those shared vertical paths are exactly where the stack effect moves air. Owners on upper floors often notice drift more in winter; owners on lower floors may notice it more from balconies and windows when neighbors smoke outside.

Corridors matter too. Many buildings supply fresh air to hallways so it pushes into units under entry doors; if that system is weak or unbalanced, air can flow the other way and bring hallway smoke in.

Sealing your own unit, most effective first

Check your HOA's rules on alterations before changing anything on a shared wall, door or fire-rated assembly.

  1. Under-sink and behind-toilet pipe penetrations

    Gaps around plumbing that runs between floors are a classic path. Seal with an appropriate sealant, and ask about fire-rated products where pipes pass through rated walls.

  2. Outlets and switches on shared walls

    Foam gaskets behind cover plates are inexpensive and easy to install with the power off.

  3. Entry door

    Add or replace weatherstripping and a door sweep, if your association allows it.

  4. Bath and kitchen exhaust

    A backdraft damper on the exhaust fan, checked by a qualified contractor, can stop air flowing in from a shared shaft.

  5. Baseboards and trim on shared walls

    Caulk the gap between baseboard and floor where air moves.

  6. Windows and balcony doors

    If drift comes from a neighbor's balcony, keep windows on that side closed at the times it happens and check the weatherstripping.

Questions for your HOA or building manager

  1. What do the declaration and rules say about smoking inside units, on balconies and in common areas?
  2. Has the corridor ventilation been checked and balanced recently?
  3. Can the association help locate the source if smoke is entering through shared shafts?
  4. Which sealing work inside my unit needs approval because it touches a rated wall or door?
  5. How should I document drift so the board can act on it?

General information for Cherry Creek, not a quote or professional advice. In an emergency, call 911.