Query multiple post of which one by taxonomy

I solved my problem by automatically adding the tag ‘light’ to all my projects. And then query all the post and projects with the light tag like this:

Query post by taxonomy tag ‘light’:

$args = array(
   'post_type'      => array( 'projects' , 'post' ),
   'tax_query'      => array(
   'relation'       => 'OR',
        array(
          'taxonomy'    => 'post_tag',
          'field'       => 'name',
          'terms'       => 'light'
        )
     ),
    'post_status'   => 'publish'
);

query_posts( $args );

Add tag ‘light’ to all projects on publish:

add_action('publish_projects', 'projects_post_type_tagging', 10, 2);

function projects_post_type_tagging($post_id, $post){
    wp_set_post_terms( $post_id, 'light', 'post_tag', true );
}

It’s not the most elegant solution but it works. If theres a better way to solve this problem i’ve would like to know.