The pipes that penetrate exterior walls bring the power, water, gas, telecommunications into a house and take away the waste.
If not properly sealed, but they can also bring in drafts, insects, mould and wood rot.
Make sure all penetrations aren’t left unsealed,like the example above, during your PCI.
Best practice is simple.
Flashing, an insulating expanding foam, or in some cases, caulk, should be present to seal these penetrations and prevent problems.