Is heat a practical way to kill structual mold?
I have to agree with Solar Mike. Sure, it might kill existing mold, by drying everything. But, it will reactivate if its cause isn't addressed...you may just need to run the air conditioner or exhaust fans more often or plug-in a dehumidifier.

Although, is there a concern? Not really. Mold is literally everywhere and in every breath you take and run-of-the-mill mold concealed in walls has no effect on people nor building products.

Now, if you mean Black Mold that's even showing up inside rooms in little patches. Then, you really MUST rip out the walls and professionally remediate it from the property.

Black Mold is EXTREMELY serious and also means you have a very blatant construction problem or water leak that's been ignored too long. In order to avoid PERMANENT health problems the issue(s) must be fixed entirely and ASAP.