
Stop Moisture and Condensation In The House
What You Should Know About ICF
A guide by the Insulating Concrete Formwork Association
What about the problems with condensation and damp?
You cannot ignore the problems that continuous moisture brings for occupants. A home filled with moist air can suffer from musty odours, damage on walls and ceilings, mildew and worst of all trace of mould.
The problem is so bad that the latest study from UKCMB, the UK Centre for Moisture in Buildings, recorded that “moisture problems have worsened over the past five years. In the UK this mostly “down to poor monitoring and maintenance, irrespective of era or construction type”.
Most concerning of all are the significant health effects it can cause, particularly for the young and elderly. According to the NHS, you are “more likely to have respiratory problems, respiratory infections, allergies or asthma” since the damp and mould can “produce allergens (substances that can cause an allergic reaction), irritants and, sometimes, toxic substances”.
This is where choosing a build solution like ICF can make a real difference, providing opportunities to improve the quality of the environment within the building, bring with it potentially significant improvements in the health and well-being of the occupants.
Why Does Moisture and Condensation Form In Buildings?
Inside the home, everyday chores and activities cause moisture to occur. Whether that’s mopping your floor, hanging laundry inside or just having a nice hot shower at the end of the day, they all impact on humidity levels in your home. The problem can be made worse depending on the internal temperature. The amount of water vapour in the air will increase, as the internal temperature increases.
When the vapour meets a cold surface, it creates condensation in the house. For example, when taking a relaxing hot shower, it creates lots of moisture in the air in the form of steam. When it encounters your wall, which is typically colder, it condenses to water creating an ideal environment for mould to form.

How To Avoid Moisture and Condensation In The House?
Can ICF Buildings Decrease Moisture and Condensation In The House?
High levels of thermal performance – With ICF, the blocks are made from two layers of an insulating material which are stacked to create the wall structure. Concrete is poured into a central cavity within the block, allowing it to sit in direct contact with the insulating block to create a monolithic and solid structure. The end result, if designed and installed correctly, is a building that offers exceptionally low U-values and excellent thermal mass and an, even, stable temperature throughout the home.
Providing superior airtightness and prevents thermal bridging – The concrete in the core of the building has a high storage capacity which, combined with low thermal conductivity, stabilises temperature fluctuations between the outside and interior of the building to minimise condensation and mould. Be aware that as an airtight structure, your designer will need to have a clear understanding on how to effectively ventilate the structure. Solutions include installing a Mechanical Ventilation Heat Recovery (MVHR) system to keep humidity at a perfect level.
Will ICF Blocks Rot
It is well-known that ICF buildings can deliver excellent thermal performance, but what about their resistance to moisture? The concrete in an ICF building is hidden by two layers of an insulating material. In the UK, the most commonly used ICF blocks are constructed from either EPS or Woodcrete.
EPS blocks have a closed-cell structure which is made from 98% air and 2% EPS, making the wall highly resistant to moisture as well as mould, rot, and mildew.
Woodcrete blocks are made from mineralised recycled timber. Woodcrete creates an above average pH environment (alkaline) which inhibits mould formation. The hygroscopic nature of the material also draws moisture from the air, thus reducing the relative humidity and preventing mould growth.
According to the ICF magazine, “A study by the Energy Materials Testing Laboratories (EMTL) nearly 30 years ago proved that EPS insulation does not absorb appreciable moisture even in prolonged, cold, damp winters. The small amount it did absorb (an average of 0.2% by weight) has little or no effect on its insulative properties”.

Other Steps To Controlling Moisture and Condensation In The House
To make sure your ICF home maximises its control of moisture levels, there are a few areas to consider.
Why Choose An ICF System From An ICFA Member?
The best way to prevent moisture and condensation in the house is to make sure you have a well-experienced supplier you can trust which is why we recommend working with our ICFA members. They have the expertise and knowledge that can provide you with peace of mind. Most importantly, getting them involved early in the design process can help avoid potential issues (e.g., inadequate ventilation) from arising.

Contact Us
Interested to find out more about how ICF can help with moisture problems? Get in touch today!
