Default Email Template when sending a new email

I have created email templates however I have found no resource at all related to setting a template as default when creating new emails within an item. For example, when I receive a new ticket in service, I can send out an automated response using Outlook, but it is only considered an update on an item and is completely separate from an email chain. For an agent to start one, it creates a separate email and each time a staff member would like to send out future responses to the customer, they would have to select the template each time.