Supaseal Glass is installing production equipment made in Austria which will allow the company to produce up to 7000 double glazing units a week. It sells 4500 a week currently.
Managing director Alex Gray decided to make the investment after seeing Supaseal enjoy strong demand for its products in spite of the downturn in the housebuilding market.
Mr Gray said the company is currently selling around 800 units a week more than it did this time last year.
It has annual turnover of more than £4 million and employs around 40 people in Hillington.
He said Supaseal has been benefiting from people deciding to spend money upgrading their existing properties rather than buying new homes.
The 55-year-old businessman claimed that Supaseal has benefited from the investment it has made in creating demand for its Saveheat glazing system among the people who will ultimately buy windows and doors that incorporate the product, rather than the trades.
For example, Supaseal has advertised in magazines and newspapers which have an affluent readership.
Mr Gray added that Supaseal has avoided selling to big housebuilders and bodies like housing associations because the margins on such sales have been cut to wafer-thin levels.
He said that some suppliers are engaged in an unsustainable attempt to secure business at all costs.
"You get a lot of them going out and trying to buy work but it does not matter how low you put your prices," he said.
"You can't create demand if it's not there in the first place."
Mr Gray, who has a stake in Supaseal, has also been able to increase demand for the company's products by acquiring window suppliers amid the downturn.
In 2008 the Greenock-born entrepreneur bought Wadds, a Newcastle-based emergency glazing specialist, with Eric Foster, who has a 50% holding in Supaseal.
In January last year Mr Gray bought Blairs, a Greenock-based supplier of bespoke timber-framed windows and timber doors, which has recently supplied glass used in historic properties in the UK and in stores in Canada.
Last summer Mr Gray took a stake in Inverclyde Windows, a customer of Supaseal.
In January this year he formed a joint venture with Mike Bryant, whose family-owned Penicuik Advanced Window Systems, to take over the Merlin Network window and conservatory business.
"If you do things properly recessions are periods of opportunity," said Mr Gray, who started in the industry in 1993 as a salesman for Highway Glass.