ABSTRACT
With the improvement in standards of thermal insulation for the building envelope, the proportion of the plant energy output Qp required to offset heat loss resulting from natural infiltration of outdoor air has increased. Modern buildings are better sealed against the random infiltration of outdoor air, but the trend towards the increasing proportion of the building heat loss which has to account for natural infiltration is continuing, since adequate ventilation of the building shell is essential, whereas there is no limitation upon the improvement in the thermal insulation standards of the building envelope.
