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February 08, 2008— Ottawa, Ontario

Infestation by different moulds on wallpaper following water damage.
Infestation by different moulds on wallpaper following water damage.

Mould plays a vital role in nature by breaking down organic materials, but it's the last thing people want to discover thriving in their home or workplace. Dr. Hans Schleibinger knows all about the impact of mould on the health of occupants and the longevity of building components. He and Madeleine Rousseau are leading a mould research project at the NRC Institute for Research in Construction (NRC-IRC), with the aim of making indoor environments healthier and giving longer life to buildings.

"In the right conditions, common building materials such as plywood, drywall, furring strips, carpets, and carpet padding feed mould. Not only can mould grow on almost any substance where moisture is present, it can eventually break down building materials," says Rousseau.

"But we're not concerned about the obvious growth of mould that can be remedied by replacing a leaky roof, windows or plumbing," adds Dr. Schleibinger. "Rather, we want to provide a scientific basis for developing new technologies to detect hidden mould, determine the degree of mould-resistance of various building materials, and model the growth of mould in various conditions in order to prevent future mould growth."

This research initiative began at a national mould S&T workshop in Montréal in 2003, led by the Institut national de santé publique du Québec in collaboration with the Institut de recherches en santé et securité au travail. There, NRC's Dr. Morad Atif, Jean-Marc Lamothe and colleagues met with representatives of the Canadian construction industry, the Canadia Mortgage and Housing Corporation, and Health Canada to begin defining the research they felt Canada should undertake. The workshop resulted in a report on research gaps and priorities on indoor mould, with respect to mitigation and health risks.

Dr. Schleibinger, Madeleine Rousseau and four other NRC-IRC colleagues then built on the workshop's findings. In a June 2005 internal report, they recommended that NRC establish a multidisciplinary approach to R&D and technology transfer and position itself to lead Canada in mould detection techniques, mould growth risk assessment, and the refurbishment of mouldy buildings.

NRC-IRC already has strong expertise in building science – particularly in the areas of moisture control in buildings, and indoor air quality. This expertise provides a valuable foundation for developing solutions to mould growth in order to contribute to healthy indoor environments and sustainable buildings in Canada.

Right now, there are considerable gaps in knowledge about mould growth in buildings. For example, there's no accepted metric for dampness, nor is there information on the effectiveness of modifying building design, construction methods, or regular building operations and maintenance in reducing dampness.

"In the first stage of our research, we plan to focus on identifying the science factors behind mould," says Dr. Schleibinger. "For example, we need to determine the "boundary" conditions for mould growth in buildings – i.e., the conditions where moulds are just able to grow, and where they are not able to grow anymore."

NRC opens new mould research labs

Last fall, NRC opened two new labs to support its mould research program. The first facility – called the Mould ID Lab – is equipped with state-of-the-art tools to identify and quantify moulds in air, in building materials, and on surfaces. These techniques are necessary to prove the links between mould growth and moisture, ventilation, building flaws and possible health effects. Researchers will use it to develop and validate reliable techniques especially for detecting hidden mould, since undetected mould growth can lead to adverse health effects in the long run. In the ID lab, building materials will be inoculated under defined conditions.

The second facility – called the Mould Growth Lab – houses a wide variety of growth chambers, in which typical Canadian building materials are tested for mould growth under "boundary" environmental conditions. Scientists can run those growth experiments at different temperatures and even at cycling humidity levels.

Severe infestation with moulds and wood rot fungi in the cavities of a house with wood frame construction. Some infestations are only detected after the occupants experience adverse health symptoms, or notice musty odours.
Severe infestation with moulds and wood rot fungi in the cavities of a house with wood frame construction. Some infestations are only detected after the occupants experience adverse health symptoms, or notice musty odours.

As he explains, previous mould growth research has been based on steady-state conditions that don't include factors such as peak relative humidity, ventilation, fluctuating temperatures over day and night, and the effects of people breathing and moving about in buildings.

"We've just opened new mould research facilities that will allow NRC to produce realistic conditions of building occupancy and generate far more valuable data and models for the building industry than steady-state studies have provided," says Dr. Schleibinger.

Rousseau works on the heat and moisture performance of building envelopes. A building envelope ― the foundation, roof, walls, doors and windows ― is the separation between the interior and the exterior environments of a building. It serves as the outer shell to protect the indoor environment and facilitate its climate control.

"We're particularly interested in the building envelope and mechanical systems parameters that foster or minimize microbial growth. This includes building construction, materials, mechanical systems and total building operation," notes Rousseau.

For more than 60 years, NRC has contributed to knowledge on moisture control and the moisture response of building materials and systems. "Now, NRC can apply this knowledge to mould issues, so that we can integrate it into solutions that can be communicated effectively to the building industry," says Rousseau.

The team's deliverables will include reliable mould detection protocols needed by health officials and building professionals to address building remediation and the health of occupants. The researchers will also develop mould growth risk assessment techniques to help the building industry reduce the likelihood of mould growth during the service life of a building.

For more information about the NRC mould research program, please contact Dr. Hans Schleibinger at

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National Research Council of Canada

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