Does MVHR prevent mould?

It helps a lot, by continuously removing moist air and supplying drier fresh air, which stops the humidity that mould needs. It does not fix damp from a leak or rising damp, which need separate repair.

Why do I get condensation in an airtight home?

Because the moisture from cooking, showering and breathing cannot leak away as it would in a draughty home. Without adequate ventilation it builds up and condenses on cold surfaces. Controlled ventilation is the fix.

Will ventilation get rid of existing mould?

Ventilation prevents the conditions that cause mould, so it stops it coming back, but existing mould still needs cleaning off. Fix the ventilation to stop it returning.

What ventilation is best for condensation in an old house?

In an older, leakier home, positive input ventilation is a common low-cost option, keeping fresh air moving to reduce humidity. Improved extract in the kitchen and bathroom also helps. Confirm the damp is from condensation, not a leak, first.

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MVHR, mould and condensation

Condensation and mould are ventilation problems at heart: they happen when moist air has nowhere to go. Good ventilation removes that moisture before it settles on cold surfaces. This guide explains how ventilation prevents damp, and how MVHR and the other systems help.

By VentRight Editorial · Last updated 2026-07-08 · Impartial · Sourced

Why ducts in cold spaces need insulating. Labelled: Uninsulated duct, Insulated duct. — Why ducts in cold spaces need insulating — labels

uninsulatedUninsulated duct — In a cold loft, the warm moist air inside the duct cools at the duct wall and condenses into water, which can drip and cause damp.

insulatedInsulated duct — Insulation keeps the air in the duct warm, so it stays above the point where moisture condenses. No condensation forms.

What causes condensation and mould in a home?

Everyday activities such as cooking, showering, drying clothes and simply breathing put a lot of moisture into the air. When that warm, moist air meets a cold surface, such as a window or an outside wall, the moisture condenses into water. Left there, that dampness lets mould grow. The root cause is moist air with nowhere to escape.

Modern airtight homes make this worse if ventilation is not sorted, because the moisture cannot leak away as it did in a draughty old house. Cold spots, such as behind furniture on an outside wall or around window reveals, are where condensation and mould show up first. It is a moisture and ventilation problem, not just a cleaning one.

How does ventilation prevent mould and condensation?

Ventilation removes moist air before it can condense, and replaces it with drier air. Extracting at source, from kitchens and bathrooms where moisture is produced, stops it spreading through the home, while supplying fresh air keeps overall humidity down. Keep the moisture moving out and it never settles on cold surfaces to feed mould.

This is why the wet rooms are ventilated hardest under building regulations: they are where the moisture starts. A continuous or well used extract system in the kitchen and bathroom, plus adequate whole-home ventilation, is the core defence against condensation. Mould treatments deal with the symptom; ventilation deals with the cause.

Does MVHR stop condensation?

MVHR helps prevent condensation by continuously extracting moist air from wet rooms and supplying drier fresh air throughout the home, keeping humidity down. In an airtight home it is very effective. It is not a magic fix for a home with a separate damp problem, such as rising damp or a leak, which need their own repair, but for everyday condensation it is a strong defence.

Because MVHR runs continuously and extracts at source, it keeps moisture from building up in the first place, which is the best way to avoid condensation and mould. If condensation persists in a home with MVHR, the system may be off, undersized or poorly commissioned, or there may be a non-ventilation source of damp to investigate.

Which ventilation is best for a home with damp?

It depends on the home. In an airtight or newer home, MVHR or continuous extract keeps moisture under control. In an older, leakier home with condensation, positive input ventilation is a common and low-cost fix, keeping fresh air moving through to reduce humidity. The right choice depends on the home airtightness and the source of the moisture.

For a persistent condensation problem, it is worth confirming the moisture is from everyday living rather than a leak or rising damp, which ventilation will not solve. Once that is clear, match the system to the home: our selector and the guide to the four system types help work out which suits.

Questions

Does MVHR prevent mould?: It helps a lot, by continuously removing moist air and supplying drier fresh air, which stops the humidity that mould needs. It does not fix damp from a leak or rising damp, which need separate repair.
Why do I get condensation in an airtight home?: Because the moisture from cooking, showering and breathing cannot leak away as it would in a draughty home. Without adequate ventilation it builds up and condenses on cold surfaces. Controlled ventilation is the fix.
Will ventilation get rid of existing mould?: Ventilation prevents the conditions that cause mould, so it stops it coming back, but existing mould still needs cleaning off. Fix the ventilation to stop it returning.
What ventilation is best for condensation in an old house?: In an older, leakier home, positive input ventilation is a common low-cost option, keeping fresh air moving to reduce humidity. Improved extract in the kitchen and bathroom also helps. Confirm the damp is from condensation, not a leak, first.