Andy Bestwick is joining Smart Solar as a non-executive director, having previously worked as managing director at Gardman until the end of 2008.
Gardman founder Paris Natar took a majority stake in Smart Solar in April.
Bestwick will work with the senior management team on specific strategic projects.
Smart Solar founder and chief executive Jonathan Stobart said: "I am delighted that Andy has agreed to join us. He has extensive market and product expertise which will be invaluable to us as we seek to grow the business. I am looking forward to working with him."
Gardman appointed Stewart Hainsworth as CEO last week, replacing Bestwick's successor Mark Pearson.