My number one SEO recommendation for a redevelopment project: do not change www usage. Here is why:
Google treats www.asite.com as a different domain from asite.com. If you change from one to the other and add redirects, then Google has to process those redirects to update every URL on your website. {Processing redirects and updating every URL in the database takes time and costs you traffic while you wait. Often, traffic doesn’t come back as strongly even if Google picks up on the change.
You can see the impact of making this change in the screenshot. This website removed www during a redevelopment project and traffic was lost almost immediately. The non-www website got some traffic, but not nearly as much. This company reverted and after a few more weeks, traffic finally started to come back up.
To be clear, www or no www can both rank in search results. The point is, though, once you have picked www or non-www as the canonical version of your domain, do everything you can to keep it that way.
