Ventilation, Air-Tightness & Insulation


A well-retrofitted home by RENOVA will not only be completely air-tight and well-sealed; most importantly it will be well-ventilated. It’s a simple fact that air-tightness and ventilation should go hand-in-hand to prevent an unhealthy living environment.

In the past, although we lived in draughty homes which were difficult to heat, they were usually well-ventilated. They were well-ventilated as a direct result of their draughtiness. Believe it or not, this was actually healthy – healthier at least than living in a well-sealed yet badly ventilated home which unfortunately we are seeing a lot more of these days. The old rattly windows and doors, badly/uninsulated walls, floors and attics were, in fact, performing two very important roles: allowing the house to breathe whilst letting the heat and moisture out.


Leading on from this, nowadays here in Ireland, in our more modern homes, we still tend to think that by opening a window or a door, all of our heat will escape, along with our hard-earned money! Some of us are even inclined to block up the air vents in the belief that we will be preserving heat, eliminating draughts and protecting ourselves from impending illnesses such and cold and ‘flu. However, the opposite is actually true – blocking up vents and not opening windows means
that moist air cannot escape which causes condensation to form and ultimately mould to grow. Another point to add is never to block an air vent by building a wardrobe in front of it. Damp manifests itself in wet patches, mould growth and a musty smell. Even if the walls are dry-lined (insulated on the inside) humid air can condense behind the insulation, causing a condition known as ‘interstitial condensation’. This occurs when dry-lining is installed incorrectly. This again encourages mould growth and is a difficult and costly problem to eradicate.

Good ventilation requires maintaining a constant flow of air within a house – fresh, clean air in, stale and moisture-laden air out. Good ventilation will remove the humid air before it has a chance to condense on cold surfaces which as we know, creates condensation and mould growth. If left untreated, damp can lead to a host of problems such as corrosion of internal finishes and even health problems, especially in vulnerable young children, elderly people and people with respiratory problems like asthma. Fresh air should constantly be flowing into our homes. Stale, moisture-laden air which is also full of unwanted gases such as C02 and Carbon monoxide and germs, should be flowing out. By eliminating stale, moisture-laden air and breathing in fresh, pure air you will notice a big improvement in your own and your family’s health. Hopefully you will even have fewer trips to see the doctor!

Over the past number of years here at RENOVA we have noticed a recurring theme of enquiry from home owners. Again –  high levels of humidity which is causing both condensation and black mould growth on external walls and ceilings. Fitting new windows, for example and having a more air-tight home without considering ventilation and allowing the house to ‘breathe’ has become the main cause of poor air quality and ‘sick building syndrome’. High levels of humidity need two ingredients to thrive: high temperatures and a supply of water vapour. As a rule of  thumb, humidity levels will double with every 10 degree increase in temperature. In other words, the warmer your house is, the more water vapour the air will hold. As your house becomes warmer, stale humid air is trapped inside. Think of all that moisture building up from showers, baths, kettles, bubbling pots and pans, steamers, tumble driers and of course, our own breathing!

Whilst passive/natural ventilation (holes in external walls) may meet building regulations, it is now widely recommended that controlled/mechanical ventilation is used to maintain a consistent flow of fresh air within the home. There are many sophisticated systems available such as ‘Heat Recovery Ventilation’. However, this can be expensive and difficult to install, especially in a retrofit situation. A cost-effective and practical alternative is an ‘Aereco Demand Controlled Ventilation’ system. Click here to see an Aereco video.

Aereco fan

DCV or ‘Demand Controlled Ventilation’ is based on the simple principle of having the optimum amount of fresh air in a home on a fully automated basis. It offers the ideal solution for both heating consumption and the quality of indoor air. When the need for ventilation is low, which is usually more than half of the time, savings can be made. More ventilation will be needed during times such as showering and cooking, when more moisture and humidity is created. Scientific studies have shown that DCV can result in a 30% reduction in ventilation losses compared to natural ventilation. Here is a photo of the inner workings of an Aereco fan similar to one we recently installed in a house that was suffering with excessive condensation and mould growth. The new Demand Controlled Ventilation system has yielded great results with improved air quality and the elimination of condensation and mould.

We hope that this introduction to ventilation has helped you to understand just how important a good ventilation system is, in particular in relation to our more modern, well-sealed and energy-efficient homes. If you can’t install a Demand Controlled Ventilation system, at least unblock those vents in your external walls and try to open your windows on a more regular basis – it will do your general health and well-being the world of good!


Remember – ‘Build Tight – Ventilate Right!’





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Tel: 01 2021122