how to disable T4 template auto-run in visual studio (2012)?

Question

I have some T4 templates in my project. Whenever I make changes and save the tt file, it auto update the generated files. This is a template that loops all tables in a database and generates about 100+ files. So visual studio hangs for a few seconds every time I save my template and this is annoying. Is there a way to disable to "auto-refresh" function and I can manually run the template through the context menu.

Thanks!