Condensation is airborne moisture which cannot escape and condenses on the coldest surface, usually resulting in window condensation.
Condensation occurs in many homes and is an expected feature particularly within period properties most commonly during the colder and wetter winter months, and most common in bathrooms and kitchens.
Because most condensation is manmade in historic properties, secondary glazing can help to prevent the airborne moisture from coming into contact with the cold primary glass – the secondary glazed panel takes on a higher temperature above dew point and therefore prevents condensation forming.
Please note: although secondary glazing helps in preventing the moisture-laden air coming into contact with the colder primary glass, one aspect that secondary glazing cannot control is the interaction between the primary and the external elements and therefore secondary glazing can highlight issues with your primary glazing, eg. rot, damp, poor ventilation.
For further information please see this independent Condensation Fact Sheet from the Glass and Glazing Federation.