How to manage mold growing along the bottom vinyl window frame of every window in an R2000 home?

To wipe, wear gloves and make a bucket of diluted Bleach (1 part bleach, 9 parts water). Use a rag or sponge to wipe the mold and clean the rag often in the bleach solution. The bleach will kill the mold and the damp rag will keep the spores down.

First, kill the mold with bleach and wipe down the whole area to try to get rid of as many spores as possible.

Next, identify and treat the root cause. Mold at the bottom of the inside would suggest that interior condensation is pooling there. Window condensation is caused by two factors:

1. Interior glass temperatures below the dew point

2. Humid enough interior air that there's enough moisture to condense on your cold windows

This suggests two potential solutions: decrease the interior humidity level, or get better windows that aren't as cold inside. Getting another dehumidifier or a bigger one is likely to be much cheaper than replacing all your windows with expensive, high-performance triple-pane units which are what you really need to stop condensation in the cold Canadian climate. Window technology has come a long way in the last 15-19 years, but it doesn't come cheap. I'd go with the dehumidifier now if the windows are otherwise in good condition, and start saving up for those better triple-pane windows. You'll feel the difference, and it will stop your condensation problems, too.

Kill the mold first (Bleach, Borax, Vinegar, etc.) then you may use thermal imager (e.g. Flir One) which can help you isolate places of possible cold leaks.

I prefer to use hydrogen peroxide (3% mixed with water) to kill mold. It does a fantastic job and doesn't stink like bleach. I learned this when working in a hospital many years ago. Just remember to add the peroxide to the water, not vice-versa. This prevents a thermal reaction, ( AAA = Always Add Acid).

Stop using bleach! It's bad for people especially kids. It can actually make your mold problem worse encouraging mold growth. There are inexpensive mold killers at Home Depot that are Environmentally friendly, like Moldex.