As Irish households spend more time indoors in autumn, cooking, showers and laundry add moisture to the air. The Department of Housing’s home-ventilation guide explains why trapped moisture can become condensation on cold surfaces in winter. It recommends keeping wall and window vents unobstructed and using the extraction provided in kitchens and bathrooms. [1]

A useful first check is a small record of how the rooms and their ventilation are used. It can help you explain a recurring problem without pretending that a window photograph identifies its cause.

Find the instructions before changing the settings

Locate the user guide for any mechanical ventilation system. The Department’s guide says it should explain operation, controls and maintenance; its advice does not replace the manufacturer’s instructions. [1]

Make a note of the controls you understand and any indicators you do not. If you rent and do not have the information, ask the landlord or managing agent for it. Do not turn a whole-house system off or dismantle a fan just to see what happens.

Walk through the ordinary moisture sources

Check that furniture and curtains are not covering purpose-provided vents. Use the kitchen and bathroom extraction according to the system’s instructions. SEAI distinguishes background ventilation from extract fans and from permanent air supplies needed by some fuel-burning appliances. Keep those permanent supplies clear. [1][2]

In the kitchen, SEAI suggests putting lids on pans to retain heat and reduce condensation. [3] At the laundry stage, decide where clothes can dry without adding avoidable moisture indoors; the Department’s guide advises outdoor drying or using a clothes dryer. Follow the dryer’s installation and operating instructions. [1]

These are checks of normal use, not directions to install vents, alter wiring or modify an appliance’s air supply. Put repairs or changes to the system in the hands of an appropriately qualified professional.

Keep a short observation record

For a week, note the room, time and location of condensation, alongside recent activities such as a shower or clothes drying. Record whether the relevant extraction was in use. A simple line might read: bathroom, morning, window wet after shower, fan running. Avoid turning that observation into a diagnosis.

If moisture keeps returning, gather the notes and any photographs for the owner, agent or professional investigating it. Ask what needs checking and how the existing ventilation is intended to operate. A general checklist cannot establish whether the cause is ventilation, a building defect or something else.

Check the user guide’s maintenance schedule and record when the next permitted routine check is due. Persistent problems deserve investigation rather than repeated purchases based only on a symptom.

This seasonal household guide uses official information checked on 11 October 2026.