Laboratory testing from Big Ass Fans ®, reviewed by researchers from top universities, has debunked the long-held belief that reversing ceiling fans in the winter recirculates heat without creating drafts.
Engineers with Big Ass Fans conducted testing that determined traditional ceiling fans, operating in reverse, caused drafts in nearly half of the room. By contrast, running Big Ass Fans ’ Haiku® ceiling fan in a forward direction limited drafts to less than 1 percent of the room and used 93 percent less energy than a traditional five-bladed ceiling fan.
Building on the study’s results, the engineering team today unveiled a patent-pending algorithm designed to automate winter fan operation and significantly reduce home heating costs. Redirecting warm air from the ceiling to occupant level allows heating systems to run less, saving users up to 25 percent1, or $200, during the winter months.
Research and Results
The practice of running ceiling fans clockwise in the winter has prevailed for decades, and the federal government mandated beginning in 2007 that all ceiling fans be manufactured with reverse switches.
Big Ass engineers conducted testing in the company’s custom residential lab sized to mimic a typical living space. Controlled for temperature and humidity, the space was equipped with dozens of environmental sensors to compare the company’s 60-inch Haiku ceiling fan and a traditional, five-bladed model of the same size.
In her review of the results, Harvard University researcher Sonya Milonova said, “The common belief that a fan must operate in reverse to destratify (mix) a room without causing a draft is disproven by this study. … Therefore, blanket legislation requiring all ceiling fans to have a reverse function is misguided.”
Milonova said traditional paddle fans are unlikely to effectively circulate heated air at a low speed, and at a high speed would create a draft.
Big Ass Fans has designed fans to operate most efficiently in the forward direction, and, with so many speed settings to choose from, have made it possible to fight heat stratification in the winter using a fraction of the power needed by a traditional fan.”
Turning Data into Smarter Heating

Results in hand, the engineering team developed the new Smarter Heating mode for the Haiku with SenseME™ smart ceiling fan, adding even more revolutionary technology to the fan that has won dozens of design and technology awards. Haiku with SenseME learns and predicts your comfort preferences using a series of precise environmental sensors and adjusts speeds based on changing room conditions.
The new Smarter Heating mode uses SenseME’s built-in occupancy sensor to detect when users leave the room and increases fan speed for rapid mixing of air. When residents return to the room, the speed automatically decreases to maintain even temperatures without creating perceptible draft.
Smarter Heating mode is activated with a tap of Haiku with SenseME’s smartphone app available for iOS and Android devices.
1Trane™ TRACE™ 700 design-and-analysis software