other Facts:

Window(s) size 3.5 feet* 5 feet (width)

Fan (2 nos.) Specifications Product page - specifications

Sweep size: 400 MM

RPM: 1280

Air Delivery: 75 CMM (What is the formula to convert CMM to CFM?)

Volume of the premise : 7200 Cubic Feet

High and Low Temperature day cycle (extreme during the year):

Month Wise Temperature Chart for the Location is available here

Summer: 45 Celcius - 29 Celcius (Comfort Target 22 Celcius)

Winter: 26 Celcius - 8 Celcius (Comfort Target 26 Celcius)

Purpose: To take the advantage of Temperature gradient between external temperature and internal temperature. Use fans during the time period when beneficial and put on Air Conditioner (Cooling and Heating) when compulsorily required to achieve last lag of the temperature target.

Note: Premise is a concrete building with no insulation, so its temperature follows the external temperature. (Heats up after external temperature goes higher and cools down after external temperature goes down)

(1) How effectively a single pedestal fan (blowing inward) can bring the outside air in the room if blades are 2 feet away from a fully open window (with the distant window of same size at the other end of the house is kept open)?

(2) How effectively a pedestal fan (blowing outward) can throw the air from the room out of window if blades are 1 foot away from a fully open window (with the distant window of same size at the other end of the house is kept open)?


(3) How effective will be two pedestal fans (one inward and one outward placed at distant fully open windows of the house) for displacing the indoor air with outside air?

  • 1
    If this question were to be answered by an air flow analysis professional they would probably be asking a whole slew of questions related to many other factors that you have not included here. The best this is probably to just try it out! And when doing that do consider why a window air conditioner is generally installed IN the window opening with a baffle to close up any extra open space.
    – Michael Karas
    Commented Jul 28, 2013 at 9:59
  • 1
    Fans blowing inwards near the floor bring in cool air, fans blowing outwards near the ceiling expel hot air. Your major goal is to provide a circular airflow that brings in cool air, puts it into contact with the interior contents to pull out the heat and then expel it. Cross flow where you pull air from the shaded side and push it out the sunny side works best. It would be more important if we knew the approximate volume attempting to be cooled, otherwise we have a lot of useless numbers. 75 CMM = 2650 CFM which is more than my powered gable vent moves. Invest in paper weights. Commented Jul 28, 2013 at 21:01
  • @Fiasco Labs Sir,I've updated the question with some more details. What is the formula to convert CMM to CFM?
    – Optimight
    Commented Jul 29, 2013 at 1:09
  • Cubic meters per min to cubic feet per min -> m3/m * 35.32 = cfm Commented Jul 29, 2013 at 1:31
  • 1
    And to figure air changes per hour -> (60 * cfm) / building volume = air changes per hour Commented Jul 29, 2013 at 1:36

2 Answers 2


While this doesn't directly answer your question, maybe you should consider a true window fan such as this one

window fan

It delivers 740 CFM, has a thermostat, is not too expensive (less than $50) and will be much more effective in ensuring the flow of outside air into the room. It's also reversible, so it can be used as an exhaust fan as well.

If you need more airflow, some models go up to nearly 3000 CFM (over 90 CMM) like this one.

  • FWIW I had one of these once and thought it was basically useless. Maybe four of them in key places throughout the house setup like Fiasco Labs described above would be a worthwhile experiment, but in my experience just one on its own will be a non-starter.. :/
    – elrobis
    Commented May 11, 2018 at 13:31

I think CFM is overrated. I use six Lasku U15700 blower style fans I bought from Sam's club several years ago when they were $40 each. They are rated at 438 CFMs when on high and can really move air around my home when I have them set up to draw air in from outside and give that air a place to go outside from inside on the other end of the house. Creating negative pressure as air blows out one end of my home makes air coming in on the other side easy to do so... with or without a fan to assist it. Cheap fans with much higher CFMs does not mean they do a better job at ventilating the air in your house. There's no doubt an Air King 9155 or 9166 will get the job done for you with CFMs between 2400 and 3000 CFMs, but one also has to factor the amount of power they use too, therefore I use timers on all my big appliances and fans and use my power company's Time Advantage rates. That said during the summer does require some careful planning and it boils down to a formula of using 85/15; that is from 8 pm ET to 2 pm ET my power rate is the same as it is in the winter, but from 2 pm to 8 pm ET every weekday I have to use 15% of my total daily power consumption to break even to normal daily summer rates. The whole goal here is reduce my power consumption and thus lower my power bill in the summer.

  • 1
    Hello, and welcome to Stack Exchange. This is interesting, but it doesn't really answer the original question. Commented May 12, 2018 at 14:24

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