5 minute read
Technical
Many will be familiar with the concepts of evaporation and condensation in everyday life. When applied to buildings, however, these principles need greater analysis. This article explores some common misconceptions around condensation and mould.
Myth 1 – New houses will not have condensation
Some believe that condensation will not occur in new homes. Unfortunately, this is misguided.
In 2014, researchers at the University of Tasmania used detailed monitoring and microbiological sampling to investigate condensation in three newly constructed homes – each of which was undergoing its first winter.
In all three homes, significant condensation was discovered. In one, dripping originating from the underside of the low-pitched roof felt like a light drizzle. The study revealed a lack of guidance in the NCC (National Construction Code) around condensation management.
In a further study funded by the Australian Building Codes Board (ABCB) in 2016, a survey was sent to building practitioners and received more than 2,000 respondents. This found that condensation was widespread across Australia and that in this aspect our code was decades behind international best practice.
Whilst some recommendations from that report were incorporated into NCC 2019, these were initial steps only, which are part of an ongoing work program, they do not, in themselves, prevent condensation and mould entirely.
Myth 2 – A home that is energy-efficient will not be mouldy
In 2010, the airtightness of buildings was upgraded amid changes to the NCC, which both increased the stringency of energy efficiency provisions and introduced a new standard for construction in bushfire-prone areas. This was considered beneficial as greater airtightness not only reduced heat loss and delivered better thermal comfort but also helped to prevent cinders from blowing into the building.
As this happened, however, copious amounts of condensation emerged in a growing number of homes. The persistent damp, which resulted has led to other problems with mould and its deleterious effects on human health.
Largely speaking, this happened because the move toward greater airtightness was not accompanied by an adequate understanding of vapour management.
Indeed, the ABCB-funded condensation scoping study found that design decisions around energy efficiency were the primary factors that affected most aspects of new home design. This included risks associated with vapour management, condensation, moisture and mould. That study concluded that there was a need for an integrated approach whereby each step of improvement in energy efficiency was accompanied by suitable measures surrounding vapour control and moisture management.
Myth 3 – There is no harmful mould if you cannot see it
In cool climates, condensation is most significant where surfaces are coldest. Often occupants associate condensation with single-glazed windows or thermally unbroken aluminum window frames. However, water vapour is insidious: it can move with air, it can diffuse through air, and it can permeate through porous material.
Given that most buildings have materials that contain high-carbon cellulose-based mould food, the addition of water pretty much guarantees mould growth.
We often don’t see it only because the action is happening in the interstitial spaces between internal finishes and external cladding. If you do see mould on the walls or ceiling, that’s likely to be the tip of the iceberg. The site of colonisation is in the dark damp interstitial spaces on the reverse side. Many of these spaces are either difficult or unpleasant to access. You are more likely to smell mould before you see it.
Myth 4 – My new house is built with new materials so it will not be water-damaged
Construction material exposure on site is of particular concern during COVID. Due to strong demand and COVID related supply disruptions, there is a shortage of building materials and longer wait times for materials to arrive on site.
This is problematic as many materials such as engineered timber, truss nail plates and particleboard flooring are not suitable for prolonged exposure to the elements.
Myth 5 – An owner is without recourse if mould were to be found to be caused by condensation
In most circumstances, this statement is mostly correct.
Mould that arises from condensation is different from mould arising from other building defects. Mould is explicitly excluded from home and contents insurance. The limitation is that the insurer is only responsible for restoring a building to a prior state prior to a ‘listed event’ covered by the policy. With the right coverage, one could be covered for water ingress from damage to the roof or arising from plumbing leaks. In such cases there will be compensation by the insurer.
However, with condensation, it could well be a problem with building design and construction — for which there is no listed event and no prior state to ‘restore’ something to. Mould remediators who are not familiar with identifying condensation causes may temporarily remove the mould, only to have it reappear next winter. The amount of condensation that occurs in buildings can be profuse, amounting to an indoor drizzle. One just has to look in the roof space on a cold morning. In the case of many houses built during the period after 6-star energy efficiency provisions were mandated in 2010, and before condensation provisions were introduced in 2019, raindrops, or more accurately dewdrops, might be falling on your head.
Published in 2015, the VBA Guide to Standards and Tolerances, which has been republished in Tasmania, New South Wales and Queensland, places responsibility on occupants with this guidance:
“Where the requirements of the Building Code of Australia (BCA) have been complied with, the responsibility for controlling condensation by maintaining adequate natural or mechanical ventilation through the use of openable windows, exhaust fans, or other means, is the responsibility of the owner. Condensation is defective if the builder has not complied with the relevant clauses of the BCA.”
For further information or to view the full article, visit https://sourceable.net/myths-andhalf-truths-around-condensation-and-mould.
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