The sale could see the closure of the Wiri and Rangiora production facilities with a loss of approximately 40 jobs.
"FIRST Union has a good redundancy agreement with CHH which will help reduce the impact of the job losses if they occur," said FIRST Union general secretary Robert Reid.
"We know that the Rank Group is trying to divest itself of its CHH operations but it seems counterintuitive that, while housing demand remains high, two panel manufacturing sites are being closed," said Mr Reid.
New Zealand Panel Group is owned by Prime Panels and a number of private equity funds.
