This paper discusses the possible passive cooling methods for Malaysian modern houses with a special
focus on night ventilation technique. A full-scale field experiment was carried out to reveal detailed indoor
thermal environment with various ventilation strategies. Night ventilation was found to be better than
daytime ventilation, full-day ventilation and no ventilation in terms of air temperature reductions during the
day and night. Night ventilation improves thermal comfort more than the other ventilation conditions based
on operative temperature. However, further measures to lower indoor humidity such as by humidification or
to increase indoor air velocity such as by the use of fan are required to improve the thermal condition in the
night ventilated room, especially in the daytime. In fact, the peak SET* in the night ventilated room was
decreased by 4.0? mainly through the use of ceiling fan, thus the night ventilation with the use of ceiling
fan was considered to be the superior option to the other conditions when the evaporative heat loss was taken
into account.