How to Verify Results: Using Temperature Loggers and Runtime Data to Validate Attic Exhaust Fan ROI

Home attic fans are supposed to cut cooling costs and keep temperatures down — but most people install a quiet attic fan and just hope for the best, never bothering to check if it’s working.

The Florida Solar Energy Center (FSEC) wanted actual proof. They ran a field study on a single-family home in Cocoa, Florida, where summer attic temperatures can soar past 130°F.

The house already had solid insulation and a radiant barrier, so they weren’t expecting dramatic gains. But still, after installing two PV-powered attic exhaust fans, the team saw a measurable drop in peak attic heat and noticeable changes in HVAC energy use.

How they tracked the results

FSEC logged temperature and power data around the clock. They wired the home with sensors and recorded data every 15 minutes to build a full thermal and electrical profile before and after the fans went in.

In the attic, they installed Type-T thermocouples to monitor air temperature. Paired with indoor and outdoor readings, these sensors showed how heat was moving through the home. During peak summer afternoons, attic temps regularly broke 130°F, but once the home attic fans were installed, peak temperatures dropped by an average of 22°F.

To see if that made a dent in energy use, they added a pulse-initiating power transducer to the air conditioner, which let them log cooling power use hour by hour. Over the test period, the AC consumed 2.8 kWh less per day — that’s about a 6% reduction in cooling energy, or 460 kWh/year.

They also logged outdoor weather conditions (solar radiation, wind, humidity) using a rooftop station, making it possible to match weather patterns before and after the fans were added, so the results weren’t skewed by changes in sun or heat.

So, is an attic exhaust fan worth it?

After installing two PV home attic fans, attic temperatures dropped by 22°F, and daily cooling energy use fell by 6%, which is about 2.8 kWh per day. That’s a measurable gain in efficiency without using a single watt of grid electricity.

More importantly, the homeowner reported that the house simply felt cooler and much more comfortable — likely a result of the lower mean radiant temperature, which affects how hot the ceilings and walls feel during peak hours.

What’s more, the PV home attic fans ran entirely on solar, without pulling from the home’s electric system. And unlike traditional models, the solar units were quiet attic fans that were nearly silent — no buzzing or motor noise.

Can you test this in your own home?

Yes, you actually can — and you don’t need lab-grade equipment to do it. If you’ve got a basic temperature logger and either a smart thermostat or a plug-in energy monitor, you’ve already got the tools to try something similar at home. You can run a short before-and-after experiment during hot weather, and let the numbers speak.

Step	Instructions
1. Track attic temperature	Use a temperature logger during hot days before installing or turning on the fan. Record peak afternoon temps.
2. Log outdoor temps	Use weather app or weather station data to provide environmental context.
3. Turn on fan and repeat	Run the same test again after fan is active. Look for drops in peak temp and how quickly the attic cools post-noon.
4. Monitor HVAC runtime	Use a smart thermostat or outlet monitor (like Kasa HS110) to track air conditioner runtime and fan power use.
5. Compare results	Look for measurable changes in attic temp and HVAC usage.
6. Pay attention to comfort	See if rooms feel less stuffy or cooler, even without changing thermostat settings.

What to track

• Start with the attic temperature. Before you even flip the fan on, place a logger in the attic and let it run for a few days. Ideally, you want a stretch of hot, sunny weather that makes your upstairs feel stuffy by mid-afternoon. Record outdoor temps, too, even if it’s just from your phone’s weather app (you’ll need them for context).

• Then switch the fan on and repeat. Once the attic exhaust fan is running, log another few days. Watch out for changes in daily peak temperatures. You will also want to spot how quickly the attic cools off after noon and how long it stays stuck above 120°F.

• Check energy use if you can. If you’ve got a smart thermostat, look at the HVAC runtime before and after. If the fan isn’t solar, plug it into an outlet monitor like a Kasa HS110 or an Emporia smart plug to track how much electricity it uses. You’ll start to see how much cooling you’re getting, and what it’s costing.

Does it feel different?

This part isn’t about numbers, but it really is all that matters if you think about it. The homeowner in the FSEC study said the house felt cooler even though they hadn’t touched the thermostat. You might notice this, too, especially in rooms that always feel hotter than the rest of the house.

Smart features give you more to measure

Basic home attic fan models flip on, run at one speed, and turn off again. That’s fine — but you won’t see much variation in your charts.

The QuietCool Smart Attic Fan does so much more. It speeds up or slows down depending on how hot the attic gets. It pushes 3,000 CFM and draws 140 watts at peak heat — about as much power as a small window AC. But once the attic cools off, it ramps down to 15 watts, still moving air but barely touching your electric bill. That adjustment shows up clearly if you’re graphing power use or attic temperature.

What’s more, installation is dead simple — just a gable mount and a plug. No electrical work needed!

The Pro QuietCool Smart Attic Fan model doesn’t have the auto-adjusting motor and instead uses a manual thermostat. You pick the temperature — say, 95°F — and the fan kicks on when the attic crosses that line. Are you in a dry climate, or just want tight control over when it runs? This gives you that option.

Both of these smart attic exhaust fans add more layers to your data and more chances to fine-tune how and when your attic stays cool.

Final tip

You don’t need to run these tests forever — just do them long enough to get a before/after snapshot. Once you see how your attic behaves with the fan running, you’ll know if it’s earning its keep!

Shop for home attic fans here

We carry a wide range of attic exhaust fans, including Quiet Cool attic fans, right here at Whole House Fan. Need free expert advice? Call us at 1.661-775-5979.