With scorching summer-time temperatures and humidity just around the corner, many of us in the northern hemisphere will start to crank up our air conditioning units (if we haven’t already). But before you close all the windows and place your thermostat in the ‘cool’ position (or put the AC unit in your window which can end up using less energy), please consider the following for your wallet’s, if not the environment’s sake.
There is no doubt that turning on the air conditioning will both lower the temperature and humidity of your living space, creating a more comfortable room. But is it always the best option? Well, sometimes. Turning on the AC during the worst of the heat waves it is unavoidable, however most summer nights offer temperatures that are quite mild and a fan could be a wiser choice (full disclosure: We live in the Northeastern United States, your mileage will vary). Now, don’t just turn on any fan in the house willy-nilly. Not all fans are created for the same purpose, and, sadly, a lot of people are unaware of the differences.
Ceiling fans can be used efficiently in not only the cooling season, but the heating season as well! Most ceiling fans have a switch on them that changes the direction in which the blades spin. During the heating season, they should spin so the air circulation is heading up toward the ceiling and down the walls . During the cooling season, they should spin such that air is blown straight down to the living space.
However, I should make something abundantly clear: ceiling fans do NOT cool or heat your home, they only blow air around. In the winter, they blow the warmer air that collects at the top of rooms (hot air rises, remember), and in the summer they help facilitate evaporative cooling, making the air feel cooler than it really is. Leaving ceiling fans running while you aren’t in the room doesn’t do much good, unless the thermostat is in that room. Speaking of thermostats, be sure to raise the temperature (or lower in the heating season) while using ceiling fans to achieve energy savings by keeping the air less stratified.
Whole House Fans
Sometimes called attic fans, these are typically large (24 to 30 inch) diameter fans that are mounted in the ceiling of the top floor of a house. They work by pulling the hot air from the top floor and blowing it out through the attic vents, allowing cooler night air from the outside to enter through open windows and doors. Doing this consumes 90% less energy on average than air conditioning. Before using, be sure the outside temperature is comparable to what you would have set the thermostat to, and that you’ve opened windows in all rooms that you want cooled (air won’t flow if there is not a complete circuit).
These do the same basic job as ceiling fans – they blow air around, making it feel cooler than it really is, but do not affect temperature. One advantage they have over ceiling fans is their ability to be more precisely aimed (directly at your face, for example).
Now, this fan advice is entirely dependent on where you live – it won’t likely do you much good if you live in Florida, but will if you live in the Northeastern US, coastal area, or any place where the night time temperature is low enough to warrant inviting it into your home. The best way to find out if a well-placed fan will help you is to try it out yourself! Experiment by using a fan to cool your room during different temperatures. This will give you an idea of when is a good night to use a fan and when to turn on the AC.
I love these things (some of you may not). Last year, I used a window fan to cool my room for the entire summer, save about 3 weeks where the humidity and heat were just unbearable at night. These actually DO change the indoor temperature by pulling in cooler air (just make sure that the outside air IS actually cooler than the inside air).
Use the right fan for the right job:
- Use ceiling fans in the heating and cooling seasons, just make sure they’re blowing in the right direction and that they’re turned off if no one will be in the room for an extended period of time.
- Use standalone fans to cool off in a more targeted way or as a source of white noise.
- Use window fans at night to pull in the air during cool summer nights.
- The same goes for whole house fans as they’ll turn any opening to a source of cool air (be sure to open windows in all rooms you want cooled)!
- Window AC units typically use less energy than whole house units but only if it is cooling a few bedrooms. Your mileage may vary.
- Most air conditioning systems can cool a space within 30 minutes after being set to temperature.
- Keep thermostats a few degrees higher in the summer and a few degrees lower in the winter.
Below is a handy chart that also summarizes (no pun intended) how to best use the different types of fans:
Protip: Half the speed (or brightness regarding dimmable light bulbs) does NOT mean half the energy used. Less energy is used, (and, in the case of lighting, well-placed dimming adds ambiance to the room) to be sure, but it is not proportionate. For example, I hooked a number of fans to a Kill-a-watt at different times and ran each of them at high and low speeds. I found that both fans used about 60 watts on high and about 40 on low. Not exactly half, but close; less noise, for sure. I recommend you buy a Kill-a-watt (or similar device) and find out how much energy your fans (and other, more costly appliances) are using!