The core idea
Temperature differences can create upward or downward air movement that redistributes moisture, odors and combustion risk.
How the mechanism works
Warm air is buoyant, creating pressure differences between lower and upper levels; leakage paths determine where air enters and leaves.
When it becomes relevant
Typical trigger: Cold weather, tall buildings, open stairwells or strong indoor-outdoor temperature differences.
Evidence that supports this interpretation
- Upper-level leakage and lower-level drafts occur together
- Symptoms intensify in colder weather
- Door position changes the pattern
Evidence that weakens it
- The pattern is unchanged across seasons
- A local fan alone explains the symptom
- No connected vertical leakage path exists
What this concept cannot prove alone
A single observation, image or meter reading cannot confirm the complete failure pathway. Use this concept to form better questions, compare alternatives and decide which safe observation would be most informative next.
Safety and professional boundary
Combustion appliances require professional testing before pressure experiments or air-sealing changes.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
