Interstitial Condensation

What is this new "buzzword" that keeps cropping up? Why only now? How come this was never a problem in older buildings? Well, the answer is simple. Additional insulation, if installed incorrectly, is one thing that can lead to interstitial condensation.

Mould behind dry liningInterstitial condensation is very simply, condensation within the structure of a building, ie. not on the surface and not clearly visible until often, it’s too late and the damage is done. Warm air can hold a lot of moisture, so air within a dwelling for example, is perfect for moisture-laden air, especially as we create so much of it – through washing, cooking, breathing, etc. Condensation occurs where this warm, moisture-laden air is suddenly cooled and can no longer hold the high levels of moisture. In a building, this is usually when the warm air meets a cold surface such as a mirror, window or external wall. If the wall is uninsulated, then it can be extremely cold in winter time and condensation will be visible on the surface...


But what happens if the wall is fitted with internal wall insulation (dry lining), for example? Now the surface is warm and there's no longer condensation...or is there...? The moisture contained in air is water vapour and is usually completely invisible to the human eye, as it is in such tiny particles. This water vapour can easily pass through most building materials such as plaster, slabs, insulation, etc. And so, they do just that...

So, your wall is insulated on the inside. This makes the external wall even colder, as now the heat cannot get out to heat it up. But the moisture can....Now, the moisture-laden air is cooled even further than before and dumps even more condensation, down along the wall surface, exactly as before...only now, the old wall surface is within the overall structure of the wall (including the dry-lining).

This is called "interstitial" condensation, as it happens within the wall’s structure. Any moisture within a structure is not good. It leads, first of all, to nasty moulds and fungi to grow within the structure which leads to very poor air quality within the building. This can have severe health implications. Dampness also leads to structural damage, whether it's rotting timber, degraded insulation, cables or pipes/fitting corroding, etc. It's a huge problem because it can't be seen for maybe several years but by then, it's far too late to do anything about it. This can equally be a problem in new and existing buildings, so great care should be taken, especially when altering the make-up of any building element eg. wall

The good news is that correct construction methods such as: using an appropriate "vapour check", a barrier against water vapour; placing the insulation in a different position, such as outside the wall, or introducing the appropriate ventilation where condensation may occur; can eliminate the possibility of interstitial condensation. It is critically important to consider what construction methods are employed before work is carried out. Unfortunately, unscrupulous or ignorant contractors may try to lead you down the wrong path as the incorrect and easy methods are generally much cheaper, quicker and easier to install.

Our advice is to do your homework first, consider all options, be sure you find a knowledgeable contractor (they are out there!) and build it right, first time! Contact us for further information.

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Client Testimonials


Dr. Roderick Peters, Newport

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In the Spring of 2013, Comfort Solutions installed external wall and loft insulation at the home I had recently bought. Before the installation, I had been concerned at how quickly the house could become cold and damp.

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Gearóidín Ní Ghrúinéil, Castle

I am very pleased with the outcome of the external insulation job on my house, completed by Comfort Solutions.

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Sean & Ann Tarmey, Ballintober

We found the house was difficult to heat and it became cold very quickly. Since the external wall insulation, attic insulation and new windows were installed, we have a much warmer comfortable home, and are making huge savings on our fuel bill. The colour render we chose on the exterior... Read more

Anonymous, Westport

The advice I received from Comfort Solutions was excellent.

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Anonymous, Quay, Westport

We have been delighted with the results of using Comfort Solutions to clad our house with exterior insulation.  The results are immediate.

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Martin Roche, Ballinamore

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I was very impressed by the no-nonsense approach of the contractor, the price was agreed the contract completion date set and I was kept informed of progress and problems at all stages of the contract, everything was completed on time with no extras, the site was cleaned up every evening,... Read more

Rachel Antoine, Monasteraden

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In 2017 I contacted Comfort Solutions to install the Lunos EAS system as a retrofitted ventilation/extraction solution for my home. The installation was carried out very well. Their work was neat and they quickly tidied up any small bits to plasterwork and surrounds. As I wasn't... Read more

Audrey Ní Fhearghail and Lorca

The external insulation that Comfort Solutions Ireland installed for us has made a huge difference to how warm our house is. From the start of the process, they proved to be professional and easy to deal with.

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Eithne O’ Malley, Westport

We had our attic insulated last year by Comfort Solutions and have been more than happy with the results.

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Barbara Bradby, Ballycroy

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Our little house by the sea in Co Mayo was a dream, but the damp was a nightmare. I looked into external insulation first as a solution for the damp which was breaking out on all the internal walls. The walls were concrete, there was condensation... Read more