Ecological Building Systems

You are shopping in

The “GB” region can deliver orders to England, Scotland and Wales. For Northern Ireland deliveries, please choose the “Ireland” region.

Your region is: Great Britain Not right?

Ask the Expert: How Do I Deal with Mould?

Niall Crosson

By Niall Crosson

Wednesday 19th January 2022

Unfortunately, mould is all too common a sight in many Irish and British buildings. The dangers associated with mould spores and the additional damage to building elements, along with poorer indoor air quality, means that it’s essential to minimise the likelihood of mould growth occurring.

Ask the Expert: How Do I Deal with Mould? Ask the Expert: How Do I Deal with Mould?

What is mould? 

Mould and mildew are fungi which favourably and rapidly grow anywhere there is an ideal temperature, moisture, substrate and a food source. There are many types of mould and their spores vary in toxicity. Mould spores are a naturally occurring phenomenon and are omnipresent, whether indoors or outdoors. Low levels of exposure to mould in the air generally has little impact on occupant health and indoor air quality. Completely removing these mould spores from our air is not possible but, when mould occurs in higher intensities and on surfaces the issue becomes more apparent and must be addressed.

What does mould do?

Mould produces allergens, irritants and in some cases toxic substances known as mycotoxins. Inhaling or touching mould or mould spores may cause allergic reactions in sensitive individuals. Allergic responses include hay fever type symptoms such as sneezing, runny nose, red eyes, and skin rash dermatitis. Allergic reactions to mould are extremely common and they can be immediate or delayed. Mould can also be a trigger for asthma attacks in asthma sufferers.

Mould on the ceiling of an apartment
Mould on an apartment ceiling caused by thermal bridging
Calsitherm insulation boards fitted to a wall which has been leveled with Diasen plaster
Calsitherm insulation boards have a high alkalinity which helps prevent the growth of mould.

How do I prevent mould?

One of the key factors which dictates whether mould can grow or not is the presence of moisture, not only as a liquid but also in its gaseous form. If the relative humidity on internal surfaces rises above 80% for prolonged periods of time there is a risk. Ensuring the living space is effectively ventilated can help reduce this risk.

Avoiding thermal bridges and air leakage also greatly reduces the risk of mould growth. Thermal bridges occur where there is a gap in the insulation layer, which leads to cooler temperatures on surfaces and an increase in relative humidity. Air infiltration of cold external air which condenses internally on warm surfaces also contributes to increased mould growth risk.

Where does mould occur? 

Mould can grow on almost any surface, even tiles and PVC, with some materials being more conducive than others (e.g. wall paper, gypsum based plasters). However, mould struggles to grow on materials with high alkalinity such as Calsitherm insulation, or on lime products such as our Lime Green range of plasters, or Diasen cork lime thermal plasters.

How do I treat mould?

First and foremost, it’s important to appreciate the health risks associated with mould spores. Where extensive mould issues arise, specialist mould removal professionals should be consulted. Off the shelf solutions are available on the market for less intensive mould infestations, however, the contributing factors which led to its initial growth should be identified and remedied.

A non-toxic off the shelf system is Auro’s PUR SAN Anti-Mould System. This consists of three easy steps. 

  1. Firstly, a chlorine-free mould eliminator is applied on the infected surface. 
  2. After this, ‘Mould Stop’ spray is applied which helps prevent the mould from reoccurring.
  3.  Finally, Auro’s breathable anti-mould paint, which is inherently mould resistant (with a PH of 12), is applied to the disinfected surface.
A carton of Auro Pur-San anti mould system

Ready to stock up on your mould-busting supplies? Browse our selection of products here!

Blog author

Niall Crosson

Niall Crosson

Technical Director (BTech, MEngSc, MIEI, CEPHC)

Niall is the Technical Director for Ecological Building Systems and was also the company’s first employee. Niall holds a first class honours degree as a Bachelor of Technology and a Masters in Eng.Sc. Niall is a certified Passivhaus Consultant and has provided technical guidance on many award winning low energy projects in Ireland and the UK, and has authored or co-authored several chapters in both the Passivhaus Handbook and the Passivhaus Designers Manual. Niall is also on the board of directors of the Irish Green Building Council and provides guidance on several national standards committees.  Along with this, Niall has contributed to several construction publications including The Journal of the RIAI.

Read More


Passivhaus Tour - Passive House Insulation Series Conclusion (part 13)

Read more

Time moves fast, keep up with design best practice

Read more
Recently viewed products

This website uses cookies to ensure you get the best experience on our website. 

View our cookie policy here.