Answers

There are companies that offer energy evaluations and some even use thermal imaging and a tool / process called a blower door reading / test.  This will help identify the cause and opportunities for correction.  You can do some easy items as well like ensuring all like plate covers have insulated pads behind the covers, check for insulation around your homes perimeter if you have an unfinished basement, check your homes exterior for small gaps or holes left from old utilities and service work performed over the years.  Best of luck!