I general, the file that is supposed to be the "home page" is named index.html, index.htm (or index.php if you are using php). This is a setting in the Apache web server and you can have an individual setting if you want another file to be your default home page. Create a file named .htaccess that includes the line DirectoryIndex homepage.html. Change homepage.html to the name of the file you want to have as home page. Upload the .htaccess file to the root of your domain directory. It might become invisible but it works anyway.
Also take a look at the wiki on .htaccess.
A better solution is to do as you did and rename the file to index.html. But if your site is very big and you have multiple links across the site and to your home page, it might be a temporary solution to add the .htaccess file.