The short answer is no, and the useful answer is longer.
Spray foam does not grow mould and does not feed it. Closed-cell foam is not an organic material - there is nothing in it for mould to eat. What foam does is change how moisture and air move through an assembly, and that change can either solve a mould problem or conceal one, depending on what was there first and where the foam is placed.
So the honest framing is not "does foam cause mould". It is: does foam fix the conditions mould needs, or does it seal them in?
What mould actually needs
Three things: a food source (wood, paper facing, dust, drywall), moisture, and a surface cool enough for that moisture to condense on.
You cannot remove the food from a house. So every mould conversation is really about moisture and cold surfaces.
Where foam prevents mould
This is the majority of cases, and it is the reason foam is used in problem assemblies.
It stops the air that carries the moisture. In most Alberta houses, moisture does not soak through walls - it rides in on air moving through gaps. Seal the gaps and the delivery mechanism stops.
It removes the cold surface. Closed-cell foam adhered directly to concrete or to a roof deck raises the temperature of the interior face. If the surface never gets cold enough for condensation, the water never appears.
The assembly this replaces is the one that causes the most mould in Alberta basements: a stud wall with batt insulation held against cold concrete, with a poly sheet on the warm side. Warm humid air finds its way past the poly, reaches the cold concrete behind, condenses there, and wets the batt and the framing - completely out of sight. People discover it years later by smell.
Foam sprayed directly on the concrete has no gap for air to move in, and keeps the condensing point inside the foam rather than on the wall.
Where foam causes trouble
Three situations, and they are all avoidable.
Spraying over a wet problem. Foam is not waterproofing. If a basement takes water, or a roof leaks, foam applied over it seals the water in and hides it. Any installer willing to spray over an active moisture source is the wrong installer. Water first, always.
Wrong placement in an assembly that has to dry. Some older walls have been managing for decades by drying in a particular direction. Put a vapour-resistant layer on the wrong side and the wall can no longer dry the way it was. The damage is slow and hidden. This is a judgement about your specific assembly, not a product setting.
Too thin. Closed-cell foam controls vapour by depth. Applied too thinly it may not keep the condensing point inside itself, leaving a cold surface behind the foam where moisture can still collect. Depth is a specification, not a preference.
Spraying over existing mould
Do not. Remediate first.
Foam will bond over contaminated material and seal the problem in place. Removing it later to deal with what is underneath is far more expensive than dealing with it now. If there is visible growth or a persistent musty smell, that gets resolved before anyone brings a rig.
What to ask before you buy
- Where is the water coming from, and is it fixed?
- Which direction does this assembly dry, and where does the foam sit relative to that?
- What depth are you specifying, and why that depth?
- Is there existing moisture damage that needs removing first?
A good installer will have raised most of these before you ask. If the answers are vague, that is your signal.
Ready to talk to someone who will look properly? Get a quote.
Related: is spray foam insulation safe - vapour barrier and spray foam - when not to use spray foam - basement insulation