The case for controlled ventilation of houses

Fresh air requirements in individual rooms of an occupied house vary between 0.5 and 2 air changes per hour depending on the number and activity of the occupants. The most common method of ventilation control is by opening windows but measurements show that even quite moderate window opening results in air change rates greater than 2 air changes per hour throughout a house.< Reports measurement of the energy cost of window opening in a test house with a heat loss coefficient of 5 kWh/K day. Finds in a low energy house,controlled ventilation is essential. Reports tests of a mechanical ventilation system which gives a constant trickle ventilation, capable of being boosted locally. Compares energy cost with the alternative of relying onwindow opening for fresh air control.