Monitoring mold risk across a portfolio
How property managers monitor mold risk across buildings: score every unit to rank them, run occupant intakes where the score is high, and re-score on any change to the record.
Step by step
Score the whole portfolio once, to establish an order
The value at scale is ranking, not individual verdicts. Scoring every address puts the units warranting attention nearer the top than ordering by age, by rent, or by complaint history would. This is a one-time exercise that produces a working list.
Re-rank by what is fixable, not by score
Split the top of the list by driver. Units carried by climate and terrain need monitoring; units carried by site drainage, ventilation or a documented event need work. The second group is where a maintenance budget actually moves the outcome, and it is usually a much shorter list.
Run occupant intakes on the high group
The structured intake is worth up to 20 points of contribution and it is the only input that comes from inside the unit — what residents can see, smell and have repeatedly reported repaired. For a portfolio it is also the cheapest inspection substitute available, because the people are already there.
Put logging hygrometers in the worst of them
A spot reading tells you about a moment. A logger left for a season tells you how often a unit spends time above 60% relative humidity and for how long, which is the persistence that decides whether anything grows. It is the only signal that catches a developing problem before a resident reports one.
Work the fixable list on a seasonal cycle
Grading and downspout discharge before autumn. Extraction ducting and its termination checked with the heating season. Gutters before and after leaf fall. None of this is sophisticated and between them they cover the failure modes behind most residential water.
Re-score on any change to the record
A completed remediation with a scope and an independent clearance. A construction year confirmed from a parcel record where it had been estimated. Work you have done does not reach the model unless you supply it, which is why a well-maintained building in a vulnerable category keeps scoring as its category.
Why complaint history is the wrong ranking
It is a lagging indicator by a season or more. By the time a resident reports a musty smell, the condition producing it has usually existed since the previous heating season, and the material behind the finish has been wet throughout.
It is also unevenly reported. Residents differ enormously in how quickly they raise something, and the quietest tenancies are not the driest units — they are frequently the ones where a problem runs longest.
A modelled estimate is the only signal available before anyone has noticed, which is the entire operational argument for using one across a portfolio.
What changes as a result
Maintenance capital gets allocated on condition rather than on age. Older stock is not automatically the wetter stock — the model's worst construction decade is the 1990s, above pre-war, because tightened envelopes without matched ventilation lost the drying capacity older buildings had.
Inspections get pointed. A surveyor attending a unit already knowing its era, cladding, terrain and documented history spends their time differently.
Disputes get a paper trail. A documented monitoring programme — scores, intakes, humidity logs, seasonal checks — is a materially different position to be in than a maintenance record that starts at the first complaint.
Cost at portfolio scale
The free check runs on any address with no account, which makes the initial ranking pass free regardless of portfolio size.
Paid reports are per property — $29, or $79 where a disclosure exists to parse, which for rental stock it usually does not. In practice most portfolios buy the paid tier only for the short fixable list rather than for everything.
Volume arrangements for managers and portfolio owners are agreed directly rather than published as a self-serve tier.
Questions people ask
- How often should a portfolio be re-scored?
- Annually, and on any material change — a completed remediation, a verified construction year, a new documented event. More often reads the same records again.
- Does this replace inspections?
- No. It decides which units get one and tells the inspector where to start. The model never enters a building.
- What about units in buildings we do not own?
- Scoring needs no ownership or permission — everything read is public record or commercially available property data.
- Can residents see their unit's score?
- That is your call. Worth knowing what you would be sharing: an estimate of conditions, not a finding about the building. Presented as the latter it says more than it can support.