A few basics about air
We believe that a well informed customer will always have a more gratifying experience. So in that regard, here is the 10 minute 'expert' course in airflow.
What we won't discuss for now are the human engineering aspects. Thermal comfort is a complex science.
What is CFM?
You see the numbers everywhere, what does it mean?
CFM stands for cubic foot per minute. This term is used as a measurement of airflow rate for ventilation systems. The cubic foot refers to a cube of air 1 foot x 1 foot x 1 foot. CFM represents a volume flow rate, since we measure how many cubic feet are flowing by per minute.
Air is really, really light.
It takes 13.5 cubic feet (101 gallons) of air to weigh 1 pound.
For a 2,000 square foot house, that means all the air in that house weighs 1,185 pounds - not much.
Warming or cooling air is “low calorie”. To warm all that air in your house up from 50 degrees F to 70 degrees F takes about 5,688 BTU’s. The smallest house furnace puts out 40,000 BTU’s per hour. So how come it takes so long to heat up the house on a cold morning? (hint: you're not just warming the air)
An unsealed door jamb, leaking 50 CFM, would over the course of 24 hours, leak out 72,000 cubic feet of air – not “low calorie.”
Does more CFM mean more cooling?
Yes, No, Sometimes, All-of-the-above.
The main function of a whole house fan is to replace hot air with cooler air , thereby cooling down the entire structure by drawing off the heat. Even with very high airflow -- say 5000 CFM -- your house can only shed pent-up heat at a limited rate. You could even double the airflow, which would greatly increase the noise, yet only speed up the cooling process by 20 or 30%. So, yes, you could speed up the cooling of your house with more airflow, but if it consumes a lot more energy, or gives you a headache, what's the point? Theory and practice lead us to conclude that efficient 'right sized' whole house fans with quiet operation provide the best results.
Operating sound levels
We challenged ourselves to create whole house fans that were quiet, with exceptional efficiency, yet would be cost effective. By utilizing low and high speeds we found that the sound level at low was barely audible, and by cooling your house through the night, substantial energy savings were achievable.
All AirScape Whole House Fans feature Premium White Aluminum Cube Core Grilles, which deliver high airflow and minimize air noise. We also designed automatic, insulated doors to provide an easy and effective barrier between living space and attic. Not only does this further reduce the fan noise, it provides a tight seal, which is important in colder climates
And, finally our ducted 2.5e, 3.5e and 4.4e line features robust industrial-grade fans that are acoustically isolated by sound deadening ducted design that further reduces noise. Astute observers will note that all of our damper doors also help reduce noise during operation (perforated - just like old phone booths).