Is it possible to remediate attic mould and spend minimum expense?

I have a 3 storey townhouse in Surrey BC. Floor dimension is 18.9’ x 36.6’ about 670 square feet. The attic has a triangle profile. The height to the top is about 13 feet.
Since I have the dryer’s vent broken for years, the humidity accumulated very much and evidently black mould grew in it. The black color stains spreads on all over the wood sheathing surface.
I want to have a remediation for this situation. Since I have limited budget I want to have an economic solution to get a safe and healthy solution.
I know that if the attic has a good air circulation it will be functioning properly. When the relative humidity is lower than 60%, the mould will be dead and new one can not grow up again.
In this case the mould and spores are inactive; we won’t be affected when living in the room. The black color on the sheathing surface is due to a combination of mould growth and enzyme staining, left behind by mould in the past. So we can leave the black color there without negative effect.
In this way attic mould problem can be resolved by a good constant air circulation, this can be the most economic solution. I want to ask specialist: I will deal with the existing mould problem in this way, is it ok by the BC’s law or the trade code please? Is it mandatory to remove the black color by any regulation please?
Thanks advance for your advice.