How to Prevent Condensation and Humidity

control humidity and condensation

Humidity control is fast becoming a priority consideration for home owners. Damp and mould are a real problem in many households in Ireland that do not have sufficient heating or that do not have adequate ventilation. If left unattended, it will result in condensation and mould growth.

Condensation is the opposite of vaporization; it refers to the process by which water vapour in the air is changed into liquid water. Examples of condensation include the water droplets on a shower door or your bathroom walls after a hot bath or shower, the moisture that appears on the outside of a cold water bottle or glass or the droplets and fog that appear inside your window during a shower of rain.

Condensation can create damage to interior paintwork, the inside surface of wall linings, floor coverings, curtains, and furnishings. Condensation will also result in increased heating costs as additional energy is required to convert condensation back into vapour which is taken up by the air as the temperature rises and can also present health hazards.

Everyday household activities such as cooking, washing, using unflued gas heaters, as well as peoples’ breathing provide the main sources of moisture that cause humidity indoors.

As condensation is formed from airborne water vapour, expelling the humid air is a crucial step in dropping condensation levels.  Correctly addressed ventilation will resolve most condensation problems by replacing moist humid air with fresh air from outside the home.

Window openings, vents and open chimneys help a building to breathe and get rid of excess water vapour but stricter Building Regulations in Ireland now demand more energy efficient and air-tight houses with features including sealed double glazed windows, central heating, etc… Therefore, Irish homes require greater ventilation design to allow the home to breathe naturally.

Condensation can be controlled in a couple of ways: firstly, by reducing sources of humidity and putting an effective ventilation system in place and secondly, by reducing the possibility of warm air coming into contact with cold surfaces.

Reducing sources of humidity

Normal vents can be quite inefficient and they can let in cold air and undo the hard work that you have done trying to keep your home warm. Luckily, there are now humidity sensitive ventilation systems available that will automatically adjust the airflow depending on the room humidity without electricity. The greater the level of humidity the more the shutters are open.

Simply opening a window can also help to control internal humidity. These should preferably be on opposite sides of your house in order to maintain a good cross air flow.

You can also use extractor fans in the kitchen and bathroom which will remove moisture at the source and stop it from travelling through the rest of your house.

Dehumidifiers draw excess moisture from the air thus helping to combat condensation, mould and damp on walls, and peeling paint and wallpaper. Dehumidifiers are designed to keep a room’s humidity levels in check, so the air is more comfortable but you do have to be careful not to over use them.

Air conditioners can also help to reduce humidity in your home. Most modern air conditioning systems are capable of regulating humidity using an evaporator coil that condenses water vapour from the air. This process occurs when hot, moist air in your home comes in contact with the cold evaporator coil. The liquid is then condensed out of the air, making your home less humid.

Having a number of plants around your home can also help to lower humidity levels. Plants extract many of their nutrients from the air and some plants can receive water from the air. Examples include the Peace Lily, Reed Palm, English Ivy, Boston Fern, Tillandsia and small cacti plants.

The steam produced by hot showers is one of the greatest contributors to bathroom humidity. To combat this problem, leave your bathroom door slightly open whenever you take a hot shower. You may also want to leave your bathroom window open part way.

Reducing the likelihood of warm air coming into contact with cold surfaces

This can be achieved through insulation. Insulated glazing units significantly reduce window condensation.

Also, make sure that the walls of your house are well insulated since warmer temperatures imply lower relative humidities.

I hope you found this article helpful. If you have any comments or suggestions on this subject please feel free to enter them in the comments box below, we’d be delighted to hear your experiences in combating condensation and controlling the humidity levels in your home.

All the best,
Oliver Dempsey
4th December 2013


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About Oliver Dempsey

Owner and Managing Director at and contributor to the Blog DISCLAIMER: All content provided in my articles is for informational purposes only. The information contained in these articles has been obtained from research carried out by myself through online and offline sources and through other writers and contributors who provide me with content. While I am responsible for the final editing of each article and I do my best to verify the information, I do not make representations as to the accuracy or completeness of any information. Therefore you must not rely on the information contained in any of these articles and always make sure to seek the advice of a suitably qualified expert before embarking on any project.
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  • tradesmen1

    We got this email below from Peter Mulholland in Cabinteely recently in response to the above article

    Oliver Dempsey

    – the piece on condensation is timely. But a I’d like to have read a
    lot more than the basics. eg: I recently had a roof reslated and then
    found that it does not have enough slate vents to meet building regs.

    Also worth consideration – or ‘condensing out’:

    how air heat recovery systems might impact on condensation levels in cold attics.
    I got two specs on insulated plasterboard for ceiling from different advisers in same company. They differ – a lot.
    to achieve an airtight (vapour tight) ceiling – advice re durability of
    vapour membranes and the best tape to use can be hard to come by
    how best to ‘water-seal’ old chimneys, cracks in gable walls, parapets etc etc
    a couple of pensioners could have avoided being caught by a cowboy
    outfit called ‘Rainwater Homes’- selling gutter installation etc
    how to block (ventilate) decomissioned chimneys (happening a lot these days)
    etc etc