Fresh air cooling uses night-time air to cool a home and all of the thermal mass indoors so it stays naturally cool longer into the day. In some climates, this can significantly cut or even eliminate the need for air conditioners. Operable window openings designed to optimize cross ventilate with prevailing cooling breezes and/or fans can be used to draw in cool outside air and distribute it throughout a home. Where fans are used, temperature and humidity sensors can help ensure only cool dry air is drawn in and filters can be used to remove dust and pollen.