FAQ: Answers to Your Questions about Air Quality

There are 2 main reasons why you found mould behind the insulation in a new house and both are related to the Building Code.

First, the Code requires that the basement be insulated prior to the new homeowner taking possession of the house. Oftentimes this means that the concrete foundation may be dry, but it is not cured and still may contain significant moisture that will evaporate into the open space between the foundation walls and the insulation. The insulation and vapour barrier makes it difficult for this moisture to disperse into the basement air, so there it sits. Any mould spores present find it much to their liking, and growth occurs.

The second issue is that it is quite difficult to seal the air-vapour barrier in the floor joist header area. The Code does not specify how this should be done, so builders sometimes staple or do not even seal the vapour barrier at all. This leaves gaps in the vapour barrier where warm moist air from the basement can make its way through to the cold foundation walls and condense. Again, this provides a very suitable environment for mould growth.

Most of the time, The Code is your friend, but not in this case, as you have discovered. The solution to your issue is to remove the vapour barrier and the existing insulation. This should be done by professionals if there is more than just a little mould. The basement should be sprayed with an eco-friendly anti-mould agent and then completely dried out using a good dehumidifier. Then new, mould-resistant insulation must be installed. Please do not use the old insulation as it has been corrupted with mould spores. Finally, an intact and properly sealed vapour barrier is a must to avoid future problems.

Thank you for your question. Most so-called “mould remediation” companies do not specialize in mould. If you look at their websites, you can see they do all sorts of remediation and restorations. From smoke and fire to floods and leaky basements, they do it all. They do air quality, they build rec rooms, they restore paintings.

One local fellow owns a home inspection service. He inspects homes for leaky windows, he inspects fireplaces, he investigates roofs and eavestroughs, and everything else… and guess what? He even detects mould as part of his overall “home inspection.” He also owns a number of individual businesses. He repairs windows. He services fireplaces. He replaces roofs and eavestroughs. Oh, and he remediates mould! Each of his businesses has its own name and website. What an expert he must be!

Find a company that specializes in mould remediation. They should detect, kill and remove mould period, and they should have been in business for at least 5 years. Those are the true mould experts. The certification process is wide open and generally meaningless in Canada, so make sure they are registered with the Better Business Bureau. Never hire a guy with a hand-lettered sign and no business cards, and avoid any company who tells you that you need their service beyond remediating mould.

That’s a great question! Please find all the details you need in our Material Safety Data Sheet.