The Cooler Method 2.0: Fall Edition
The Cooler Method Is Back: Why September Is Perfect for Natural Cooling
Back in June, we coined a little home-cooling strategy we called The Cooler Method.
The idea was simple: take advantage of Wisconsin’s cool overnight temperatures, bring that air into your home, then “close the lid” in the morning and hold onto it for as long as possible.
It worked great in early summer.
Turns out, September may be an even better time to bring it back.
Late summer and early fall in Wisconsin often give us some pretty dramatic temperature swings. An afternoon can still reach the upper 70s or 80s, while nighttime temperatures fall into the low 60s, 50s, or occasionally even cooler.
Instead of immediately reaching for the thermostat when another warm September afternoon shows up, you may be able to use the weather itself to do some of the cooling for you.
If you missed our original explanation, you can read more about The Cooler Method here.
September Gives You a Bigger Head Start
The real advantage isn’t simply that it’s cooler outside at night. It’s how much of a head start you can give your home before the next warm afternoon arrives.
Imagine waking up to a 60-degree morning with an afternoon high of 82 in the forecast.
If your house is already 72 degrees and sealed up for the day, the AC may eventually need to kick on as the sun warms the house.
But if you’ve spent the overnight hours bringing cooler outdoor air inside and start the morning at 64 or 65 degrees instead, your home has a much bigger temperature buffer before it becomes uncomfortable.
That’s the September version of The Cooler Method.
You’re not trying to keep your house refrigerator-cold all day. You’re simply starting cooler and making the day’s heat work harder to catch up.
Open Up When the Temperature Drops
Once the outdoor temperature falls below the temperature inside your home, that’s your opportunity.
Open windows and let the cooler air move through the house. A fan placed near a window can help pull cool air in or push warmer indoor air out.
Opening windows on opposite sides of the home can also create a cross-breeze that moves air much more effectively than opening a single window.
The longer that cool air has to circulate overnight, the cooler the walls, floors, furniture, and other materials inside your home can become too.
And that matters because your home isn’t just a box full of air. Everything inside it can absorb and hold heat.
Cool more than just the air, and your home has a better chance of staying comfortable the following afternoon.
Then Close the Lid
Here’s where the “cooler” part comes in.
Before the outdoor temperature starts climbing again:
- Close your windows.
- Shut blinds or curtains on sunny windows.
- Keep exterior doors closed when possible.
- Avoid adding unnecessary heat inside the house.
You’ve essentially loaded your home with cool air overnight and are now trying to keep as much of it inside as possible.
On the right September day, you might make it well into the afternoon before your air conditioner needs to do anything at all.
And on some days, it may never need to turn on.
September Is Also a Great Time to Use Your House Differently
During the middle of summer, avoiding indoor heat can feel like a losing battle. In September, little changes can make a surprisingly big difference.
Cook outside or wait until evening.
An oven running at 5 p.m. can quickly undo some of the cooling you saved throughout the day.
Close blinds before the room gets hot.
Blocking afternoon sun works much better before the sunlight has already heated the room.
Use ceiling fans when you’re actually in the room.
Fans don’t lower the room temperature, but moving air can help you stay comfortable at a slightly warmer indoor temperature.
Watch the forecast instead of the calendar.
September weather can change quickly. One day may be perfect for open windows while the next is humid enough that you’ll want the AC handling moisture again.
Know When the Weather Isn’t Helping You
Cooler doesn’t always mean better.
If the outdoor air is especially humid, bringing it inside can make your home feel muggy even if the temperature drops.
The same applies when outdoor air quality is poor because of smoke, high pollen levels, or other conditions.
In those situations, keeping the windows closed and letting your HVAC system manage the indoor environment may be the better move.
A quick look at the temperature, humidity, and air quality before opening the house can tell you whether Mother Nature is offering free cooling or just inviting herself inside.
One Last Chance to Give the AC a Break
September is a funny month in Wisconsin.
One morning you’re wondering whether it’s too early to wear a sweatshirt, and two days later you’re turning the AC back on.
That’s exactly why The Cooler Method works so well this time of year.
Those cool nights can help carry your home through the remaining warm afternoons, reduce how often the AC runs, and maybe even help you squeeze through some September days without mechanical cooling at all.
We originally introduced The Cooler Method for early summer, but don’t retire it with the Fourth of July decorations.
Late summer and early fall might be its prime season.
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