Since Colorado legalized recreational cannabis, plenty of metro Denver homes have seen indoor use, and some have hosted home grows. Neither is unusual, and for many buyers neither is a deal breaker in itself. What concerns buyers is the lingering odor, and in the case of grows, what the odor might indicate about humidity, ventilation changes and wiring.
Cannabis smoke behaves much like tobacco smoke in a house. It leaves a residue on hard surfaces, soaks into fabrics and carpet, and travels through ductwork. Its smell tends to be sharper and more recognizable, and many buyers will name it immediately. Vaping and edibles leave far less residue, but heavy indoor vaping can still leave a film on windows and smooth surfaces.
A grow room is a different matter. Plants release moisture, and a room run warm and humid for months can leave mold on drywall and framing, musty odor in carpet, and stains under the paint. Many home grows also involved added venting, extra circuits or covered windows. A buyer's inspector will notice those things whether or not any odor remains.
Smoke residue versus former grow room
| Question | Smoke residue | Former grow room |
|---|---|---|
| Where odor sits | Walls, ceilings, fabrics, HVAC | Drywall, framing, carpet, closet and ventilation paths |
| Main hidden risk | Residue bleeding through new paint | Moisture damage and mold behind finishes |
| Other things an inspector may flag | Rarely anything beyond odor and staining | Added circuits, vent penetrations, blocked windows, water staining |
| Typical first step | Cleaning residue from every surface | Moisture and mold assessment of the room |
| Who else may be needed | Painter, HVAC cleaning | Electrician, drywall repair, mold professional |
Matching the response to the situation
- IfOccasional indoor smoking, mostly in one roomThenClean that room thoroughly, replace the HVAC filter, prime and paint. Recheck with the house closed.
- IfHeavy smoking throughout the house for yearsThenTreat it like a long-term tobacco home: remove soft materials, wash all surfaces, address ducts, and consider a whole-house treatment before finishes.
- IfA former grow in a closet, basement room or garageThenHave the room inspected for moisture and mold before cleaning or painting. Ask an electrician to look at any added wiring.
- IfVisible mold on drywall or framingThenHave the extent assessed and handled properly rather than painted over. Mold removal is a separate job from odor treatment.
Signs of a former grow an inspector may spot
- Extra vent holes in walls, ceilings or closet doors
- Patched holes where ducting or fans were mounted
- Added outlets or a subpanel not original to the house
- Water staining on ceilings or subfloor in one room
- Reflective paint or residue from foil on walls
- Window coverings sealed or painted over
General information for the Denver area, not a quote or professional advice. In an emergency, call 911.