Thread: Can Fans cool your house on a hot summerday when no one is home?

I know some people who leave fans on in their house during hot summer days when no one is home, believing that this practice will keep their home cool until they return in the evening. When you tell these people that this practice is a waste of electrical energy, and their house may actually be warmer when they get home, they usually come up with excuses such as, that they want the air to be circulating, etc.

I remember some years ago, elderly people in France died during a heat wave, because their residences were not air conditioned. Could these deaths have been prevented by using methods and equipment that might have been available to them?

I had a large fan located in a hallway that sucked the air from the entire house and blew it up and out through the attic so it circulated the air very well. It made a big difference during the summer months so much so that my parents didn't put AC in for over 15 years after it was available

Circulating hot air in a closed environment won't help much. If AC were to be installed that would have helped allot.

Yes, I open the attic/loft hatch in hot periods. This allows hot air in the house to go up into the roof, rather than it getting trapped in the bedrooms.

Unless you are using fans to replace air in the house, they will not be effective unless blowing on your skin, because that increases evaporation and takes heat away from your skin - latent heat of evaporation?

Fans blowing air around an otherwise closed house with nobody at home will do very little except perhaps to equalise the temperature and remove hotspots, but as cosmic says, they will increase heat overall due to the heat from the fan motors.

OB

Originally Posted by Janitor

I know some people who leave fans on in their house during hot summer days when no one is home, believing that this practice will keep their home cool until they return in the evening.

This will usually keep your home cooler. It's what we do and works well.

One beer is right. If fans merely circulate air in a room, it will raise the temp due to the heat generated by the motor. To test what I say, come home after leaving the house all day with any fan on, turn off the fan, and try to touch a metal part of the motor (even the fan's axle will do), and be prepared to jerk your hand away quickly. What people actually feel when they come home is that circulating air is more refreshing than still air, even if it's a bit hotter. It would be better to put the fans on timers to turn on a few minutes before arriving home.

In addition to other methods given here already, one method of keeping a house cool is to close the windows and draw the shades or close the blinds to keep as much of the sun's radiation out, and sometimes you can even continue this through the evening. A roommate showed this to me years ago. It works best with well-insulated houses.

Another method is to use window fans blowing out of high, sunny windows of the house, and leaving doors open to allow air to circulate through the house. Also allow air to enter the house from low, shaded windows — cellar windows if possible.