Rooms, readings and psychrometrics

Room Analysis is where most of a damp & mould survey’s evidence is captured: one card per room, each carrying its own readings, checklist, and photos.

What it is

Adding a room opens a card for Relative humidity (%), Temperature, and Surface temperature, plus a Water Activity (aw) value, from which the app calculates Dew Point, Vapour Pressure, Absolute Humidity and Mixing Ratio — the standard set of psychrometric values used to judge condensation risk, calculated on-device with no server round-trip. Water activity above roughly 0.70 is the threshold generally understood to support mould growth. A ventilation-adequacy check, plus optional detail on room volume, extraction type and rate, and background/purge ventilation, sits alongside the readings. A defect checklist (cracked walls, poor drainage, leaking pipes, insufficient insulation, cold bridging, and more) and a photo section, using the same photo pipeline as everywhere else, complete each room.

The Environmental Sensitivity Matrix (mould risk matrix) is a separate, explicitly-labelled simulation: it projects surface relative humidity across a range of temperature shifts while holding the room’s current moisture level constant, colour-banding each projected value from green through to red/severe. It’s a way of visualising how sensitive a room is to a temperature drop, not a second measurement.

How to do it

1. Add a room and name it.
2. Enter your readings — relative humidity, temperature, surface temperature, and water activity if you’re taking it.
3. Review the calculated psychrometric values that appear alongside your readings.
4. Tick any relevant items on the defect checklist, and complete the ventilation-adequacy check and, where enabled, the extended ventilation detail.
5. Add photos for any hazard finding — required if your organisation’s photo policy applies.
6. Review the mould risk matrix if you want to see how sensitive the room’s projected surface RH is to a temperature change.
7. Repeat for each room in scope, including any your organisation has marked as required.

How it integrates

Room readings feed directly into the survey’s overall condensation analysis and, for damp & mould, the HHSRS scoring — see Condensation and U-value analysis. The defect checklist is shared between room and external findings, so the same vocabulary applies whichever you’re recording against. Photos attached to a room finding follow your organisation’s photo policy exactly as described in Photos, geotagging and the photo policy.

Common problems

• I don’t see the extended ventilation fields. They’re an org-level setting (on by default) — ask an admin if you expected them and they’re missing.
• The mould risk matrix shows a severe band and I’m not sure what that means. It’s a projection, not a live reading — a red/severe band means the room’s current moisture level would put surface humidity into mould-favourable territory if the temperature dropped by that much, useful context alongside your actual readings, not a replacement for them.
• A required room is missing from my list. Required rooms are set by the office when the job was raised — check the job’s briefing shown when you first opened it, or ask the office to confirm.