The plant, at the company's hometown of Ste-Marie-de-Beauce, about 230 kilometres east of Montreal, employs 300 to 350 people at the peak of the annual manufacturing cycle.
Bocenor, which currently employs about 900, said it will concentrate production at its three other plants which it says are profitable. Its brands include Bonneville and Polar.
Bocenor management said the decision followed the failure of cost-cutting negotiations with the factory's workforce.
"The Ste-Marie-de-Beauce plant has been unprofitable for several years due to overly high operating costs, especially its payroll," said the company, 59 per cent owned by the Quebec Federation of Labour's Solidarity Fund and 30 per cent by the family of interim CEO Dennis Wood.
"In addition, its performance has further deteriorated in recent years as a result of an unfavourable exchange rate."
Union spokesmen were not available for comment.
The company said it opened negotiations in December "to improve labour flexibility and reduce the hourly wage rates to bring them closer to the rates in effect in the rest of the window and door industry and Groupe Bocenor's other plants."
However, discussions "have been in vain and no common ground has been found."
Bocenor went through a court-protected restructuring in 2004, in which it dropped some product lines, closed an aluminum products plant and withdrew from some costly American markets.
It now concentrates on eastern Canadian and east-coast U.S. markets.
Bocenor announced last month the sale of its Multiver division, which makes sealed glass units.
Bocenor earned $1 million in the three months ended Nov. 30, 2005, up from $200,000 a year earlier, although sales declined to $29.5 million from $37.6 million because of the re-organization including the sale of Multiver.
Founded in 1946, Groupe Bocenor calls itself is one of Canada's largest window and door manufacturers.
Its shares were unchanged Monday at 44 cents.