We are homeowners, not HVAC professionals. This page documents what we observed with the fresh air intake system.
The Issue
| Item | Observation |
|---|---|
| Fresh air flex duct | Runs from an exterior hood into the main return plenum |
| Filter screen | Missing during home inspection. CBH added a light-blue screen afterward. The screen had no label, no MERV rating, and no maintenance instructions. Gaps around edges allowed air to bypass the filter. |
| Duct connection | The flex duct pulled away from the exterior wall outlet. The plastic collar tore through the screw holes. A zip tie was loosely holding the duct near the wall. |
Detached duct in the attic
Timeline
- Pre-closing inspection: Independent home inspector flagged missing filter screen.
- Post-closing: CBH added light-blue filter screen (no label or MERV rating provided).
- April 2025: Discovered flex duct had pulled away from exterior wall outlet. See Fresh Air Intake Disconnection.
- Summer 2024: Replaced original screen with MERV-1 pad.
- After 2 months: MERV-1 pad showed significant debris accumulation.
Evidence
Original Filter (no rating)
MERV-1 Filter after 2 months (Summer 2024, fire season)
Air quality monitor readings:
| Scenario | Before filter replacement | With MERV-1 pad |
|---|---|---|
| Wildfire smoke events | Indoor readings reached “Unhealthy” within an hour | Readings reached “Moderate” |
| High-pollen days | Spikes observed on monitor | Lower spikes observed |