Cover exterior foundation with XPS insulation

Stucco is often used for this. Has to be flashed carefully, and if there are termites in your area you will need a termite barrier.

HTH,

Paul F.

It's generally referred to as "pargeing"

Termites and carpenter ants love chewing on foam insulation. If the existing rigid insulation foam isn't treated with insecticide a termite barrier won't help much. Burying an end of the untreated stuff is shooting yourself in the foot. The OP has to determine exactly what foam was used and make sure he's not covering up a future big problem.

I do not have termites in my house. For 10 years I live in it I never saw a single termite.

Termites do not come from inside the house, muchacho. They live in subterranean hives. The hives can be many yards down and many yards away from your house.

Code requires a concrete foundation have 8" exposure above grade - some codes require 6", IIRC. One of the primary reasons for this is so that the termite mud tubes (which they build to protect themselves from drying out when they're not undercover) will be noticeable.

Having buried foam provides termites an easily chewable, ready-made mud tube replacement that would hide termite activity.

Perhaps one of the reasons you haven't had termites is that you haven't extended the buried big pink foam insulation welcome mat.

I find it most curious that you decided to comment on your termite- free house history (to the best of your knowledge), instead of whether the foundation foam on your addition is treated or not. Is it?

Do yourself the favor and Google it - foam insulation foundation termites carpenter ants.