Trying to choose the right quantity and capacity of fans to efficiently and frugally cool our house?
Post
TLDR: In order to cool the space using the outdoor air, how many fans would you buy, where would you place them, in what direction should they be, and at what CFM capacity? To elaborate on the title, I live in a house and I'd like to buy a few box fans to sit against the window screens to help burp the house, rather than rely entirely on central air cooling ($$$). By the time I got home at 6:00PM in Southern California, it got to 90 degrees Fahrenheit inside. With all windows open and central air circulating outdoor air (no cooling) for 4 hours, I got it to decrease a mere 3 degrees F. Outdoor air approx 70 degrees through this time and a wind ranging between 3-7 mph from top of image to bottom of image. I am under the impression that buying fans will pay off long term as we enter the summer, but who knows, maybe not. Also very interested in simply being energy efficient though. We do have a central air system, but why use that when the ambient air is so cool at night right? Assumptions, Constraints, and Priorities: We are trying to cool the hot rooms using the cool outdoor temperature. Natural winds are usually light to negligible. Keeping some windows open through the day is unfortunately a bit of a theft risk. The rooms with vaulted ceilings seem to be significantly hotter, or at least harder to cool due to the volume. Priority #1 = Living Room Priority #2 = Bedroom Priority #3 = Office My other considerations How feasible is it to significantly cool an 85-95 degree house in ~2 hours with fans only anyways? Should I keep the central air circulating outside while the window fans are on? It is my understanding that CFM is the main consideration when buying a fan (and decibel volume) Comparing indoor temp and outdoor ambient, what's a reasonable point to So... I am probably way over-providing here, but at the end of the day if this were your house, how many fans would you buy, where would you place them, in what direction should they be, and at what CFM capacity? Looking to be cost effective but still achieve the goal. Willing to spend a couple hundred bucks for the fans. Reading sub rules after I typed all the above out: - The size of their house in square feet or square metres = 800sqft - Wall thickness = ~6in - Pane of windows = all single pane - Location/climate = Southern California, USA - Include the model numbers and size of the heat pump as best you can = not easily accessible, but looks like an appropriately-sized split system with the outdoor unit sitting in the sun without shade most of the day.
Intent Score
34
Intent
86
Confidence
Summary
The post is about cooling a house with fans and open windows, but it does not indicate a window replacement or repair problem.
Reasoning
The author mentions windows as part of a ventilation/cooling strategy and discusses placing box fans against window screens, but there are no signs of broken, drafty, foggy, old, or inefficient windows needing replacement. This is broader home comfort/energy-efficiency planning rather than a window service intent.
Extracted Signals
- windows used for ventilation
“I'd like to buy a few box fans to sit against the window screens to help burp the house”
- home cooling/energy efficiency concern
“rather than rely entirely on central air cooling ($$)”
- mentions windows in a broader comfort question
“how many fans would you buy, where would you place them, in what direction should they be, and at what CFM capacity?”
Model: gpt-5.4-mini · Prompt: v3 · 6/12/2026, 9:01:24 AM