Without enough ventilation, homes regularly suffer from condensation on windows, walls and floors. For well over 20 years, more widespread use of central heating, making windows and doors more airtight, installing sealed double glazing, sealing of open open chimneys and flues have made it necessary to change the way existing houses are ventilated. In the last 10 years or so, major changes in the way new homes are ventilated have been reflected in updates to building regulations - the most recent in England and Wales came into effect in July 1995 as an amended Approved Document F1. Refurbishment gives an opportunity for improving ventilation in existing housing so the builder and householder need to be aware of the guidance given by local building regulations. This Good Repair Guide explains the changes to Approved Document F1 and gives advice on avoiding some of the problems that can confront the builder.