Break the mould: How to keep your home condensation-free

Revealed: The essential strategy to win the war against condensation, damp, black mould, and mildew

There are ways you can actively fight condensation issues before you can afford investment solutions such as reducing water run-off around windows. File picture

Did you know that a family of four (two adults and two kids) release approximately 20l of water vapour back into the air just through breathing? Buttoned into the house after hours, the atmosphere in many older homes is downright clammy. Condensation issues can be misidentified and even exploited by unscrupulous cowboy contractors as rising damp or other weatherproofing/structural issues in the home.

Peeling wallpaper, pooling water on windowsills, musty smells, mysterious winter coughs and visible black mould and mildew. Your breath combined with normal domestic activities, could be wreaking havoc on the interior environment, particularly during these darker months.

So, what is condensation? Basically, it occurs when moisture in the air, those tiny unseen droplets touch a cold surface, reach what is termed their dew point, and return to a watery state. 

The warmer the air is, the greater its ability to hold moisture as vapour. If the air is laden with moisture (100% humidity), and there are cold surfaces for the vapour to settle on — the more likely there is to be condensation. You may regularly find a few dribbles of liquid around the base of older double or single glazing after a cold night, especially those cloaked in heavy curtains. The warm air heaving with moisture falls down through the room as it cools, hits the window and condenses.

There are other sly signs that your ventilation is not up to the job. Is the sugar clumping if left in a bowl in the kitchen? It’s ingesting moisture.

Breathing, cooking, bathing, boiling — it all releases vapour into the air. In managed quantities (50%-70% is standard) this humidity keeps our air comfortable. However, without sufficient air exchanges — it’s a problem, especially in winter when we are sealed up in a weather-tight home with reactive, fossil-fuel heating peaking and plunging temperatures over 24 hours. 

Even where you have passive forms of ventilation such as open fireplaces, if you close the doors the air can be fattening up with moisture vapour with as little as a single whole-house air exchange in one day.

Think about your north or east-facing outside walls — how cold they are during the night? If the air in the bathroom has been sodden with a couple of showers, and your mechanical ventilation is not up to the job (or simply doesn’t exist), that moist air will inevitably cool, settle on tiles, ware and walls, and condense. In areas of the house where you cannot see where the condensation is happening, things can spiral unseen. 

Behind furniture in a cold room where you hang a few things to dry during the day, walls reach dew point during the night. There could be a slime festival unfolding simply because we closed a wall vent.

Condensation is the number one culprit for black mould — not rising damp. Aspergillus niger needs pure water to thrive, and condensed water is actually very clean — ideal for biological vagrants to party. So, short-term without diving into major expense, what can we do this weekend to freshen the air, and at least put a hold on chronic condensation issues? Condensation can and does happen in some airtight A3-rated new homes where the ventilation elements need remedial work. We’re going to keep it simple — by reducing moisture and increasing ventilation with what you could term — managed draughts.

Heating

Don’t just use your central heating to make the surroundings feel dryer — it doesn’t work. Remember, the warmer the air is, the greater its ability to hold moisture as vapour — the moisture that can lead to condensation is still there and damp air is harder to heat than dry air.

Bathrooms

Starting with steamy scenes of the bathroom — relatively cool after hours and often marked by exterior walls. If you cannot get a mechanical vent installed in short order, think about rapid ventilation (opening a window) or sharing the burden of that humid air between better-ventilated spaces. If you have a shower room adjoining a utility room, try cracking the window in the utility and leaving the door ajar if privacy allows. 

Have tough, able youngsters, open the window slightly during showers and throw it wide for a few minutes when they’re finished with the bathroom door firmly shut. If there are wall vents in place, ensure they are open. Go outside and check for obstructions caused by climbing plants. At ground level, vents should be cleared to breathe (don’t do high work —get in a pro — especially if you are of a certain age).

Laundry

If you have a tumble dryer, unless it is condensing water into a reservoir that is pumped outside or collected and poured away, your machine must be vented to the outside. Periodically, take a peek at the venting hose fixed on the reverse leading to the wall vent. These are easily punctured but can be replaced with an adaptor kit for your model for under €20. 

Do not — I repeat do not — dry clothes in any space without adequate ventilation, or the addition of a dehumidifier or some sort of water-collection drying rack. Influencers fluttering full loads of wet washing on elaborate radiator devices are misguided. Next time you see a nostalgic pulley model hovering over an ancient Aga, note the cottagecore speckling of mildew to the ceiling.

 

Back in the bathroom, reduce the relative humidity by all means. Watch shower durations and temperatures. Consider adding a window squeegee to your shower routine. Whip this over any glazed panels and down the tiling and send that moisture down the drain. If you have a cordless window vac use that too.

Humidity

If someone is leaving the place clouded up like a Turkish bath, they are likely boiling up your heating bills. When using your hob to boil or simmer, run the extractor fan while cooking and for a few minutes afterwards to freshen and dehumidify the air. If it’s not a through-draught design, prop a window too to aid that air exchange. In winter, we’re trying to balance air quality against heat loss. Special care should be taken for vulnerable family members — the young, physically challenged or elderly.

Windows and vents

Something that’s often overlooked (apart from the German practice of Lüften — opening the windows and doors on brighter, warmer days to cross-ventilate the house) is the power of window vents and the narrowest window-latch. 

These tiny inclusions can offer a trickle of fresh air exchange that’s useful in the bedrooms as you snore through the night. 

If vents are articulated, try opening them up even with curtains closed, and prop the bedroom door too to share moist air across more cubic metres. Check tightly built wardrobes for signs of mildew, ventilating them with small grills or propping them open to let air circulate.

Longer, consistent heating cycles will manage condensation better than short hits as it takes time for exterior walls to warm up and to do what they can do quite well — act as heat stores and return warmth to the building. Otherwise, they operate as condensation panels.

Ventilate rooms

If you have rooms that you know are going to be cold during part of the day and night focus on ventilating them, don’t just simply heat them periodically. Dehumidifiers are a proven weapon for drying out a damp house, but you must follow their maintenance to the letter.

On the bright side of spring, go further. Investigate more comprehensive improvements to reduce moisture and to ventilate the surplus vapour off successfully. Be guided by an independent damp survey carried out by a qualified engineer. Retrofits might include loft-mounted, positive input ventilation (economical and highly effective), mechanical ventilation units, and improved wall insulation (EWI or the wrap and dry lining).

Look up grant-aided help through the Sustainable Energy Authority of Ireland, seai.ie, and the low-interest, home improvement loans from financial institutions including your local credit union.