Andy,
Great question. The height of the header is not fixed (when no hight is specified, it’s default is auto) so the header will adjust to the content inside.
Instead of setting a height, I’d suggest adding some padding to the top and/or the bottom of the header. That will let you affect the height without causing any trouble with the site’s responsiveness.
To add padding, place this CSS snippet inside the Custom CSS box on the theme options page:
header.primary {
padding-top: 20px;
padding-bottom: 20px;
}
Just adjust the top and bottom values until you get the fit that you’d like.
If you run into any questions, just let me know,
Bill