Unlike the winter measurements, the daytime and nighttime ventilation
rates were significantly different (p < 0.05) from each other; the daily daytime averages were consistently higher than the measured nighttime ventilation
rates by as much as 54%.
In cool or moderate climates, a passive solar house will not require any air conditioning and will be comfortable inside simply with natural nighttime ventilation
A nighttime ventilation
fan system pre-cools process areas and monitors interior air quality and carbon dioxide.
It simulated nighttime ventilation
for office, restaurant, school, and retail buildings in various regions of California.
Specifically, a designer may estimate the ventilation rate needed to offset internal gains when direct ventilation can be effective and the internal gains that may be offset by nighttime ventilation
when direct ventilation will not work.
During the summer, and in climates with adequate variation in temperature and good prevailing winds, nighttime ventilation can be used to cool down the building, reducing air-conditioning loads.
With nighttime ventilation systems, the building is often shaped to minimize air-flow obstructions:
If we keep that up, we should be have her home on just nighttime ventilation
. That would make life a lot easier during the day."
In advance of hot days, an exposed concrete ceiling slab is precooled through nighttime ventilation
to provide heat absorption capacity on the following afternoon.
If the outdoor temperature at night is higher than about 65 degrees or if the outdoor air is humid, nighttime ventilation probably isn't appropriate.
This nighttime ventilation strategy can be accomplished simply by opening windows to allow night breezes to flow through the home.
Notably, PCM achieves greater savings in moderate climates with large diurnal temperature swings and lower summertime humidity levels, i.e., where nighttime ventilation
can be used to cool and re-solidify the PCM without creating moisture issues.