You can promote a team member to team admin from the team member list (on the Envrmnt menu, under Account Settings > Team). On the row listing the member you want to promote, select on the Role. A pop-up menu will appear, and you can click on Admin to promote that user. You can do the same to demote the user back to Member again.
Team admins have essentially all the same permissions as the owner, but they are not the point of contact for the Envrmnt administrators, and so are not responsible for billing and payments.
Team members only have access to all assets and experiences, for now (we'll soon add project permissions for team admins to grant selectively). Team members cannot add or remove other team members.
A team may have only one owner. If you choose to promote someone else to an owner, you (the current owner) will lose that status and will be demoted to a member.