Positive Input Ventilation

Condensation

Positive Input Ventilation

Positive input ventilation is a loft or hallway unit that dilutes humid air in UK houses where condensation, not rising damp, is marking cold walls and windows. It is specified after that diagnosis, and it does not replace a missing damp proof course. Request a quote with the form or WhatsApp.

Positive input ventilation is for homes where condensation, not rising damp, is marking cold walls and windows.

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Symptoms

What people notice first

Condensation already diagnosed, with streamed windows and mould on cold walls

A house with a loft, or a hallway position, where extracts alone are not enough

Upstairs rooms that stay humid overnight

What's included

Check that condensation is the main problem
Loft or hallway location assessed
Unit sized to the house
Existing extracts in kitchens and bathrooms reviewed
How to run the system explained

What this visit does not do

Not a fix for penetrating damp, a leak, or rising damp
A flat with no suitable location may not take a loft unit
The unit needs a suitable power supply; a dedicated electrical alteration is an electrician’s job if the existing circuit is not adequate

Method

How the visit runs

Condensation is confirmed first. Loft or hallway location, the size of the house, and the extracts in wet rooms are checked. The unit is sized to the house. You are shown how it should run, including through winter.

1

Investigate first

We map the stain, take moisture readings, check salts where plaster has blown, and look outside at ground levels, gutters, pointing and the damp proof course line. The damp type is written down before any treatment.

2

Treat the path that is wet

Rising damp, rainwater, condensation, a bridged cavity or a wet cellar each get the repair that closes that path. A damp proof course is used only where groundwater is the cause.

3

Leave a record and a drying time

You get a treatment record and the guarantee that applies to the system installed. Plaster and paint wait until the readings say the wall is ready. Decorating a wet wall brings the mark back.

4

What changes the price

The price follows the unit, wiring, loft access, and whether extra extract fans are needed in wet rooms.

5

After the visit

Leave it switched on in the heating season. Clean or replace the filter. Do not block the hallway diffuser with a tall cupboard.

6

What fails if this is skipped

A unit with a clogged filter barely moves air, and the mould returns. Maintained, it keeps diluting humid air for the life of that unit. It does not dry a rain-soaked wall.

A desk fan or a small dehumidifier is not positive input ventilation. They do not bring the same steady air change through the whole house.

FAQ

Questions

These are the questions for this job. Wider damp questions sit on the FAQ page.

All FAQs

No. An extract pulls wet air from a bathroom or kitchen. Positive input brings drier air in, usually from the loft, and dilutes humidity in the whole house. Wet rooms still need their own extracts.

The unit tempers loft air. It is not a heater and it is not an open window all night. The survey says if the house is so leaky or so cold that ventilation alone will not deal with the mould.

Sometimes, with a hallway unit, if condensation is the cause and there is a place to put it. Many flats are better served by working extracts. We will say if a loft unit does not fit.

Filter cleaning or replacement as the manufacturer sets out, and a check that it has not been switched off. A dead unit is a common reason mould returns two winters later.

Condensation Management Systems

Expert Damp Surveys & Diagnosis

Rising Damp Specialist Treatment

Penetrating Damp Solutions

Coverage

Areas we cover

The same survey runs in these counties, and across the rest of the UK.

Greater London Greater Manchester Kent Devon Cardiff Edinburgh

See all areas we cover

Next step

Your building, diagnosed before it is treated.

A loft or hallway unit that dilutes humid air when condensation is the diagnosis.

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Positive Input Ventilation