hi, u will need to call local glazing specialist as units are 2 sheets of glass vacumn sealed. its because ur seal has broken down (usually down to age ) that causes this, i guess this window of yours faces alot of sunlight? break down sooner because of this but u should still get 10yrs+. hope this is helpful. willing to help if ur anywhere nr me, wolverhampton? jon.
john west
December 2008