The issue at hand occurs when the seal that encircles the perimeter of the sealed unit deteriorates, thereby permitting moisture to penetrate, which consequently results in condensation accumulating between the two panes of glass. During the manufacturing of double glazing, either air or gas is encapsulated and hermetically sealed between the glass panels, establishing an insulating cavity that serves to conserve heat within your residence while effectively obstructing the ingress of cold air. Nonetheless, over time, this seal may degrade, leading to the manifestation of misted units and a subsequent reduction in the overall thermal efficiency of your home. Certain companies propose a remedial approach that involves drilling a hole in the glass to eliminate the moisture. However, it is vital to note that this method does not include resealing the glass, which significantly increases the likelihood of future issues. In my professional opinion, it is far more judicious to replace the entire unit to guarantee enduring efficacy. I encourage you to reach out to me directly, as we provide services across Gateshead, South Shields, Sunderland, Washington, Houghton-le-Spring, Durham, Chester-le-Street and Peterlee. I would be pleased to arrange a visit to your property to measure the glass that requires replacement, and I will provide you with a complimentary, no-obligation quotation. Should you find my pricing acceptable, I will proceed to order the new glass and subsequently return to your property for installation. The obsolete units will be responsibly removed and recycled accordingly.