Damp route checker + dehumidifier sizing

Condensation, a building fault, or both?

Start with where and when the moisture appears. If the signs fit condensation, the tool will size a dehumidifier, choose compressor or desiccant, and show the running cost.

Nothing is uploaded or saved
Step 1

The space

One damp room, or damp through the whole house? Pick the scope, then set the floor area.

What are you drying out?
Quick presets

Not sure? An Irish double bedroom is roughly 12–16 m², a box room 6–9, and a typical living room 18–22.

Step 2

The conditions

Damp level affects capacity. Temperature decides whether a compressor or desiccant machine is the better fit.

a) How damp is it?
b) How warm is the space?
c) Do you dry laundry indoors?
Step 3

Where and when does it show?

This cannot diagnose a building remotely, but the pattern can tell you whether buying a dehumidifier is a sensible first move.

Choose the strongest sign
When is it worst?

Measure away from a radiator, open window or the dehumidifier outlet. A single reading is a snapshot; a few days of morning and evening readings are more useful.

Your result

Likely route and machine size

Pattern check

The pattern fits condensation

    If you are managing condensation, this is the size to buy Capacity is based on the space, severity, laundry load and real-world performance in cool rooms.
    — L/day —

    —

    50–60% RH
    A practical target range. If humidity is already below 60% but one spot stays wet, investigate the surface or building.
    —
    — at your rate (— kWh/hour)
    —
    Estimated running cost at 6 hours a day, 7 days a week. A humidistat should cycle the machine off once the target is reached.
    Safety and health: stop an active leak, avoid disturbing extensive mould, and get professional advice if damp affects electrics, ceilings, structural timber, sewage, or anyone with significant respiratory symptoms.
    The honest bit

    Why the rating looks larger than expected

    Headline litres-per-day ratings are measured in warm, humid lab conditions. A real Irish room at 15–19°C extracts much less, particularly with a compressor model. The recommendation allows for that performance gap. It is a practical sizing estimate, not a guarantee of daily water collection.

    Measure the humidity, then buy for the room you have

    The matching machine type is highlighted. A cheap hygrometer is the first purchase if you have not measured the room.

    Compressor dehumidifiers (12–25 L) → Desiccant dehumidifiers (8–10 L) → Digital hygrometer → Heated airer + cover →

    A machine manages airborne moisture and drying. It cannot repair a pipe, roof, gutter, wall, drain or ground-level defect.

    Irish damp, condensation and dehumidifier FAQs

    How can I tell condensation from penetrating damp?

    Condensation usually favours cold surfaces, windows, external corners and areas with poor airflow, and worsens in cold weather or after moisture-producing activity. A patch that tracks rain, a local stain beside plumbing, or a low-wall tide mark needs the source investigated rather than being labelled condensation.

    What does the dew point tell me?

    It is the temperature at which the room air becomes saturated and water can form on a surface. If the tool gives a dew point of 11°C, a window reveal or wall surface at 11°C or colder can condense even though the room air feels much warmer. The calculation does not measure the actual wall temperature.

    Compressor or desiccant?

    A compressor model is more efficient in a heated living space. A desiccant model keeps extracting in a cold, unheated room where a compressor loses performance. A cool room between those conditions can suit either, depending on whether low power use or extra warmth matters more.

    What humidity should I aim for?

    A practical target is 50–60% relative humidity. Use a hygrometer and the machine's humidistat rather than running continuously. If readings are normal but a single area stays damp, that points away from a whole-room humidity problem.

    Will a dehumidifier cure rising or penetrating damp?

    No. It may help dry materials after the source is fixed, or temporarily reduce moisture while work is arranged. It does not repair rain entry, a leaking service, bridged damp protection, ground levels or another building defect.

    Is a dehumidifier useful for indoor laundry?

    Yes. Use it in a closed room with the clothes airer, allow airflow around the laundry and keep the filter clean. The water then goes into the tank rather than spreading through the home.