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.

Subscribe to our mailing list

* indicates required
Email Format

Client Testimonials


Amy Healy. Glenisland

I upgraded the boiler in my home and needed a heating solution for my office which is in a separate building.
Comfort solutions advised on the best possible solution for my unique circumstance. I am delighted with my new heating system and the level of control it offers. I... Read more

Martin Roche, Garadice

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.

Read more

Happy Customer, Newport

I decided to have the insulation of my 2005 built house checked after finding it difficult to keep the rooms warm during the bad winter of 2015/16. Draughts, cold spots and a boiler that was always on the go meant it was time to do something. After a lot of... Read more

Anonymous, newport

I decided to have the insulation of my 2005 built house checked after finding it difficult to keep the rooms warm during the bad winter of 2015/16.   Draughts, cold spots and a boiler that was always on the go meant it was time to do something.

Read more

Margaret McMenamin, Westport

Solar Service

I would certainly recommend this Company for their excellent service.  Having had some bad experiences with other contractors they were true to their word in that they telephoned me when they said they would and turned up on the due date.  The service was carried out in a very... Read more

Matthew Warrington, Claremorri

In 2016 Fergus and his team installed Lunos ventilation systems into various rooms in our house. In the bathroom and en-suites moisture is now automatically removed, while the system in a sitting room provides fresh air. That particular room maintains a good, even temperature.

Additionally, we suffered from water penetration... Read more

Helen McLoughlin, Ballindine

Cavity Wall & Loft Insulation

I'm delighted with the service from Comfort Solutions! I would have no hesitation in recommending them to friends. My home is now so warm and snug - thanks Fergus


Read more

Liam Moloney Derrybeg

Comfort Solutions were for me the ideal solution in providing a complete package of home energy and insulation improvements. I also appreciated their prompt and reliable service

Liam Moloney, Derrybeg, Co. Donegal

Read more

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.

Read more

Tom Healy, Ballina

From start to finish my experience of Comfort Solutions has been very good. I found the Company to be first class in particular Fergus McManamon. I am delighted with the final product and I am in no doubt we will see the benefit of it way into the future.

Tom Healy,... Read more