# Condensation on Windows | Condensation Mould in Dublin URL: https://dublincleaners.ie/blog/winter-condensation-mould-dublin-homes/ > Condensation on windows from November to March: why it happens in Dublin homes, how to ventilate, dry clothes indoors safely and stop mould. Call 01 230 8646. Seasonal # Condensation on Windows in Winter: Stopping Mould in Dublin Homes ![Lana, founder of Dublin Cleaners](/img/lana-founder-dublin-cleaners-96.webp)By [Lana](/author/lana/), Founder of dublincleaners.ieUpdated 14 November 2026 Quick answer Condensation on windows forms when warm, moist indoor air meets cold glass, and it peaks in Dublin from **November to March**. Cut it by running **extractor fans** when cooking and showering, keeping **trickle vents open**, drying washing **outside or in a ventilated room**, and wiping glass each morning. The HSE links damp homes with **mould on walls and windows**. Key takeaways - SEAI's 2026 technical standards describe condensation as moisture in the air depositing on cold surfaces due to reduced ventilation and breathability. - SEAI lists stuffiness, odour, mould and condensation as evidence of inadequate ventilation in a home. - SEAI's standards say all wet rooms, such as a bathroom, shower room or utility room, should have an extract fan. - The HSE advises using an extractor or opening a window when cooking or showering, and drying washing outside if you can. - The HSE lists mould spores among the common causes of allergic rhinitis, which affects about 1 in 5 people. - Dublin Cleaners cleans mould from €95 for one room and €120 for a whole bathroom. Condensation on windows is the first sign of winter in many Dublin homes. From November to March, cold glass and warm, moist air meet every morning, and water runs down onto the sills. Left alone, that moisture feeds black mould on frames, curtains and wall corners. This seasonal guide explains what causes it and what to change. ## Why does condensation on windows get worse in winter? Condensation gets worse in winter because the glass is colder and homes are sealed up to keep heat in. SEAI’s 2026 technical standards describe condensation as moisture in the air depositing on cold surfaces due to reduced ventilation and breathability. Colder glass and less fresh air mean more water. Everyday life adds the moisture. Showers, cooking, kettles, breathing overnight and wet washing all release water vapour. In a small apartment with windows closed, that vapour has nowhere to go except the coldest surface, which is usually the window or an outside wall corner. SEAI also notes that cold spots, called thermal bridges, can cause damp cold walls, condensation build-up and mould growth. That is why mould often starts behind wardrobes, in ceiling corners and around window reveals. ## How do you know if condensation is causing mould? Condensation mould shows as black spots on window seals, frames, sills, wall corners and the backs of curtains. It is worst on north-facing and outside walls. SEAI lists stuffiness, odour, mould and condensation as evidence of inadequate ventilation, so mould is a ventilation warning, not only a cleaning job. The HSE says moulds and fungi grow on walls and windows in damp houses. It lists mould spores among the common triggers of allergic rhinitis, which affects about 1 in 5 people. People with asthma or allergies tend to notice symptoms first. Damp from a leak or rising damp looks different. It usually appears as a tide mark or a patch that stays wet in dry weather. Where black spots have already spread, our [mould cleaning service in Dublin](/mould-cleaning/) treats one room from €95 or a whole bathroom from €120. ## How do you stop condensation on windows? Stop condensation by removing moisture where it is made and letting fresh air in. Run extractor fans during and after cooking and showering, keep trickle vents open, and air rooms for a few minutes each morning. Keep the heating at a steady, moderate level rather than short blasts. Habit Effect on condensation Notes Extractor fan on while cooking and showering Removes moisture at the source SEAI says all wet rooms should have one Trickle vents open Constant background ventilation Never cover or tape them shut Lids on pots Less steam into the kitchen Free and immediate Bathroom door closed during and after showers Keeps steam in one room Open the window once the fan has run Wiping windows each morning Stops water reaching seals and sills Wring the cloth into the sink Furniture a few centimetres off outside walls Lets air reach cold walls Common mould spot behind wardrobes The HSE gives the same core advice: use an extractor or open a window when cooking or showering to prevent condensation, and keep bathroom curtains clean. SEAI’s standards add that where a kitchen or utility room under 6.5 m² has no outside wall and cannot be aired by a window, the extract fan should run on for 15 minutes after use. ## How should you dry clothes indoors in winter? Dry clothes outside whenever the weather allows, as the HSE advises. Indoors, use one room only, close its door, open the window slightly or run a dehumidifier, and keep the airer away from walls. Avoid bedrooms, where people already add moisture overnight. Draping wet clothes over radiators puts the most moisture into the air in the shortest time. A tumble dryer vented outside, or a condenser dryer with its water tank emptied, keeps that moisture out of the room. Spin clothes at the highest setting the fabric allows before drying them. ## How do you clean condensation mould safely? Clean small patches of surface mould with a mould spray, following the label, while wearing gloves and with the window open. Wipe, rinse and dry the surface. The HSA’s home chemicals leaflet says to read the label, use the recommended amount and never mix chemicals. Never mix bleach-based mould sprays with vinegar or other cleaners. Wipe window seals and the bottom rubber gasket carefully, because mould hides in the groove. Wash affected curtains on the hottest setting the label allows. For larger areas, or mould that keeps returning, fix the moisture first and then clean. The [guide to cleaning mould from walls](/blog/how-to-clean-mold-from-walls/) covers painted surfaces and ceilings in more detail. ## What should renters do about winter condensation? Renters should ventilate and heat reasonably, and report broken fans or missing ventilation to the landlord in writing. The RTB’s minimum standards say a rented home must not have damp and must have proper heating and ventilation that tenants can control. Dated photos help if there is a disagreement later. Mould is a common source of argument at the end of a tenancy. Our guide to [mould in a rented house in Ireland](/guide/mould-in-rented-house-ireland/) sets out who is responsible for what. Cleaning mould off is only half the answer if a fan has failed or vents are blocked. Want a fixed price instead? Call 01 230 8646. Give us the bedrooms, bathrooms and area, and we will give you a price on the phone. [01 230 8646](tel:+35312308646)[Request quote](/contact/) ## Frequently asked questions Is condensation on windows normal in winter? Some is normal on cold mornings, especially in bedrooms and on single glazing. Heavy condensation that runs down the glass every day, or that forms on walls, means too much moisture and too little ventilation. SEAI treats persistent condensation and mould as evidence that ventilation is not adequate. Should I open windows in winter to stop condensation? Yes, briefly. Open windows for a few minutes after showering, cooking or first thing in the morning, then close them. Keep trickle vents in window frames open all the time. Short bursts of fresh air remove moist air without cooling the walls and furniture much. Is it safe to dry clothes on radiators? It puts a lot of moisture into the room, which ends up on the coldest surfaces. The HSE advises drying washing outside if you can. Indoors, use an airer in one room with the door closed and the window slightly open or a dehumidifier running, not a bedroom. Does a dehumidifier stop condensation? A dehumidifier lowers the moisture in the air, so less condenses on windows. It helps most in a room used to dry clothes or a flat with poor ventilation. It does not replace extractor fans in the kitchen and bathroom, which remove moisture at the source. How do I clean black mould off window frames? Wipe the frame and seal with a mould spray, following the label, in a ventilated room while wearing gloves. Do not mix it with any other cleaner. Wipe dry afterwards. If mould keeps returning or covers more than a small patch, the moisture problem needs fixing first. Who fixes condensation in a rented home? Both sides have a part. The RTB's minimum standards say a rented home must not have damp and must have proper heating and ventilation that tenants can control. Tenants should use that ventilation and avoid blocking vents. Report a broken fan or vent to the landlord in writing, with dated photos. ## Sources 1. [SEAI, Domestic Technical Standards and Specifications, Version 4.0 2026](https://www.seai.ie/sites/default/files/publications/Domestic-Technical-Standards-and-Specifications.pdf) (2026-07-01) 2. [HSE, Living with asthma (mould and damp)](https://www2.hse.ie/conditions/asthma/managing-your-asthma/) (2026-11-14) 3. [HSE, Allergic rhinitis](https://www2.hse.ie/conditions/allergic-rhinitis/) (2026-11-14) 4. [Residential Tenancies Board, Minimum standards for rental properties](https://rtb.ie/renting/rights-responsibilities/minimum-standards-for-rental-properties/) (2026-11-14) 5. [Health and Safety Authority, Use Chemicals Safely at Home and in the Garden](https://www.hsa.ie/media/1nfngryi/use-chemicals-safely-at-home-and-in-the-garden.pdf) (2026-11-14) ![Lana, founder of Dublin Cleaners](/img/lana-founder-dublin-cleaners-192.webp) About the author: [Lana](/author/lana/) Founder of dublincleaners.ie, Lana's company brings expertise in both residential and commercial cleaning services fostering a clean, healthy environment. Outside of work, you'll often find her hitting the gym or immersing herself in invigorating body balance classes.