Since it's the exterior of the building that would be someone who has at least 10 years’ experience in the field of residential building design. Also, check with your local cities building and safety department to see if they will require a building permit for the type of work you are proposing, (probably not since the work you described is non-structural in nature) and if they require a licensed architect for the type of work, again probably not. Hope this helps a little.....if you have more questions I would be more than happy to help point you in the right direction....