The Curse of Condensation, Mould & Mildew | Michael Tweed

Michael Tweed

The following comment was submitted by Michael Tweed MRIAI to BRegs Blog on 20 April 2017.

In the course of my work through a typical winter I’m regularly asked to investigate problems of condensation and usually associated mould and mildew in apartments. My experience leads me to conclude that in Ireland the outbreak of condensation is mainly seasonal, usually starting around the beginning of October and running though to around the middle to end of April, depending greatly on the particular autumn and spring weather.

The problem has little to do with how well the apartments retain heat. Apartment blocks are a heat efficient design for dwellings because they cluster dwellings together decreasing the proportion of apartment envelope that is exposed to the elements. Rarely do I hear complaints about the cost of heating the apartment.

The cause of the problem of condensation is poor ventilation resulting in rapid build-up of the moisture content of the air when the apartment is occupied. (It is salutary to look at the amount of air borne moisture the average person emits into the air over a 24 hour period. I even encountered air borne moisture build-up in a poorly ventilated apartment from the pet cat which was kept indoors all day!) And the poor ventilation is usually a result of misguided reliance on natural ventilation in the apartment.

Yet despite apartments having an inherent energy efficient design and natural ventilation being practically useless as the means of providing adequate rates of ventilation in apartments, the guidance to the building regulations recommends compliance with energy conservation for apartments through unnecessarily excessive building insulation (and an obsession with cold bridging which I can’t understand given our temperate climate)  together with compliance with ventilation through crude reliance on natural ventilation. This is the reason for poor quality apartments where black mould is the norm.

The risk of condensation is reduced by ensuring the moisture content of the air in the apartment is low. It’s an easy correlation to remember – less moisture in the air, less risk of it turning into condensation! Which is where ventilation comes in, replacing the stale moist air with fresh air from outside. However, in Ireland through the winter the air has a low temperature and high water content (simply because we’re a small island and no matter what direction the wind blows the air travels over large bodies of water!). So there is an inherent problem which is that the replacement air has a high water content to begin with! So as Mike Morris observes in relation to the matter of insulation, tackling the problem of condensation is complicated! Compliance with conservation of energy has to occur in tandem with compliance with ventilation.

In order to construct good quality buildings that are both energy efficient and condensation and mould free we must use construction technology and techniques that address the unique problems presented by our indigenous climate. Using research from somewhere with a completely different set of climatic parameters won’t work. And the guidance to our building regulations in regard to conservation of energy and ventilation MUST be based on sound scientific peer reviewed research and development that is carried out in Ireland and is specific to our unique climate.

The problems and risks addressed by other parts of the building regulations, the likes of structural stability, fire safety, sound, design of stair and ramps, and access for all are common almost worldwide (with a few exceptions such as designing for earthquakes etc). But the problems and risks associated with the conservation of energy and ventilation are unique to location, geographic and most importantly climate. Part F and Part L must be absolutely specific to Ireland and Ireland only.

Other posts of Interest:

Could Rapid Build Housing mean Rapid Fire Spread? | Michael Tweed B.A. B.Arch RIBA MRIAI

Nearly Zero Energy – Ireland’s Next Construction Scandal | Mike Morris

nZeb are Homes of the Future | Minister Damien English

Alert | Near Zero Energy Building (NZEB)

Irish government in row over passivhaus eco building regulations | The Guardian

Building Regulations Part ‘L’ – Made Easy | Mike Morris

Design risks to comfort and health of occupiers | Architects Journal

Breaking the Mould | Joseph Little Architects

Building industry objections to passive house are deeply flawed | Passive House +

Fire Safety in Green, PassivHaus and Energy Smart Housing | CJ Walsh

Notes from the (thermal) edge: Part L Compliance (2 of 2) | Look Back 14

Part L compliance – Who wants a building control service provided by cowboys?

One ‘L’ of a battle looming over DECLG Building Regulations | Michael Tweed

Part L compliance issues – S.I.9 (1 of 2)

Part L- is compliance worth the paper its written on?

Design Certifiers – 3 things about certifying Part L… 

Why the design certifier and architect need third party building fabric assessments

Opinion piece: new building regulations and materials risk analysis

SI.9 and Part L | Specialist ancillary certifiers Part 2

SI.9 and Part L | Are specialist ancillary certifiers needed? Part 1 

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