This is a bit of information that I share with my clients:
From the exterior of your home walk around and find any gaps in the siding where water pipes and electrical wires enter the house. Once you have identified them, fill all gaps with caulk to seal out pests and moisture.
Then enter the crawlspace, again look for any gaps and seal then from the inside.
Once you have the gaps sealed, recommend wrapping all hot water lines with insulation. This will not only decrease heat loss but will also decrease your water heating bills.