Mold risk by ZIP code
How to run a mold risk check by zip code: a ZIP shows the regional moisture burden every property there shares. It cannot separate two houses on the same street.
What changes at each level of detail
| Level | What it can see | What it cannot |
|---|---|---|
| Metro | Climate, precipitation, flood-claim history and the dominant housing era across a whole market. | Anything about a neighbourhood, let alone a building. |
| ZIP code | The regional moisture burden — 20 of the model's 100 points — plus the general housing stock of the area. | Terrain, which varies street to street. Construction of a specific house. Any disclosure history. |
| Address | All four modules: regional load, terrain and drainage at those coordinates, the building's own record, and its documented water history. | Current conditions inside. Undisclosed history. Maintenance nothing recorded. |
What a ZIP-level figure actually is
It is the regional component, and nothing else. Twenty of the model's hundred points cover the climate a building has to cope with — humidity, rainfall, flood exposure, storm exposure — and every property sharing a postal code starts from the same figure for those.
That makes a ZIP genuinely useful for one question: how much background pressure do buildings here work against? A high-humidity, high-rainfall ZIP means envelopes in that area are being tested harder, and it is a reasonable input into deciding how much scrutiny a purchase there deserves.
It is useless for the question people usually bring to it, which is whether a particular house is a problem. Eighty of the hundred points are about the property — its ground, its construction, its history — and none of those are constant across a postal code.
Why the variation within a ZIP is larger than between ZIPs
Terrain moves in metres, not miles. One house at the bottom of a shallow depression and another sixty metres away on the rise have different drainage classes and can differ by six or eight points on that module alone, in the same postal code, on the same street.
Housing stock is rarely uniform either. Most established neighbourhoods carry several construction eras, and the era curve spans thirteen points between its best and worst decade. A ZIP-level average of that is a number nobody's house has.
And the largest module, disclosure and event history, is entirely property-specific. It cannot be averaged in any meaningful way, which is why an area figure quietly omits nearly half the model.
How to use an area figure well
As a screening step across a portfolio or a search area, to decide where to spend attention — not as a finding about any one address in it.
As context for a score you already have. A property scoring Elevated in a low-burden ZIP is being driven by the building or its site, which narrows what to look at. The same score in a high-burden ZIP may be mostly climate.
As a reason to ask better questions about local construction. Areas with a dominant era carry that era's failure modes at scale, which is worth knowing before viewing anything.
Coverage
Regional profiles are held per postal code, so an area figure is available anywhere in the covered footprint. Full four-module scoring — which is what an address gets — runs in Pennsylvania, New Jersey and Delaware, where the terrain profiles and the state disclosure forms are supported.
Questions people ask
- Can I see mold risk trends for my neighbourhood?
- At postal-code level you can see the regional moisture burden, which is stable rather than trending — climate normals move over decades. What varies meaningfully within a neighbourhood is terrain and housing stock, and those need addresses.
- My ZIP scores low. Is my house fine?
- It means the regional component is low, which is 20 of 100 points. The other 80 are about your building, your ground and your record, and a low-burden region has plenty of wet houses in it.
- Why not just publish a map?
- A map at postal-code resolution would show one number that is true of the area and of no individual property in it, and it would be read as the latter. The metro index publishes area-level comparison honestly, as a ranking of markets rather than a verdict on buildings.