Gives results of a statistical survey of energy consumption in British government buildings. Suggests one reason for high consumption may be excessive ventilation. Reports field trial of the effect of reducing natural ventilation in a London office building. Window frames were sealed with a rubber mastic, giving an annual fuel saving of 22%. Finds measure was highly cost effective with a payback period of less than three years.< Discusses problem of heat loss through large doors in hangars and workshops. Gives example of reduction in energy consumption by fitting hangar doors with proximity switches and nylon brush seals.