AirScape Engineer's Blog

We’re happy to announce that the 4.4e WHF is currently in stock and we’re moving product out the door.

What makes this an “e” ?  The motor is an ECM (electronically commutated motor) which when matched up with the efficient blade design gives a great power profile and low noise.

See the details here: http://airscapefans.com/products/Shop/Natural-Cooling/Whole-House-Fans/AirScape-4.4e-WHF

The following graph shows the energy use profile of the 4.4e as compared to the theoretical efficiency of a fan system.

Even though railroads are much more energy efficient and deliver lower transportation costs without federal subsidies, why are trucks the preferred mode of transportation?

I think that the answer lies in the fact that the highway truck combination is effectively open source.  The term open source is commonly used in the software world, but it applies here as well.

The platform is a highway, which just about anybody can use, provided they obey rules for weight, size, and safety of their modules (trucks in this case). This gives a tremendous amount of freedom to truckers and shippers to control their own destiny.  Ask anybody who has used the railroads for shipping and you will see that a rigid central planning department controls how and when your freight arrives.

How about this for an idea. Let’s make the railroads into a regulated monopoly. (It works for electricity, water, and gas BTW). The railroad makes its income by maintaining the infrastructure.

We get a lot of questions about the ‘R value’ of our damper doors, so we felt that it’s worth going over the basics.

The so called ‘R value’ is denominated in  the units of (square-feet x degree x hour/ BTU). Sounds complicated, but all you really need to know is:

Heat Flow  Q (in BTU per hour) = Area x (temperature differential) / R-value

[For you techies, this formula is valid for steady state, and assumes an infinite plane area.]

Let’s do the math for our whole house fan dampers.  We’ll assume VERY cold conditions in the attic (0° F) and 70° F inside.

Bottom line:  There is not much heat loss through a well insulated whole house fan damper door.  The question that you SHOULD be asking is: “How well sealed is the whole house fan damper door?”

Most residential windows will have R values of 1 to 3. Another question that we get all the time is : “What is a BTU ?”

BTU stands for British Thermal Unit.

1 BTU is approximately the energy released by burning 1 paper match.

100,000 BTU’s make up one therm – that’s how you purchase natural gas, and right now that costs about $1.50

A gallon of gas has about 114,000 BTU.

The picture at right represents some of the contrasts that  we observed on our recent trip to Europe. Outside of the room, you can see a building that is anywhere from 100 to 300 years old. Every window has shutters which have been used for years to keep noise and light out.

In contrast our hotel room (and every hotel room we stayed in) was equipped with modern windows that make North American models look primitive. As expected, the windows open along the vertical hinge, but the cool feature is that with the twist of the handle, they can be made to tilt open leaving a secure ventilation gap at the top.  When closed, the window seals like an airplane door, which makes for almost zero air leakage.  The good seal was further appreciated, considering that the street is about 2 feet from the window.

“When you have a hammer, everything looks like a nail”

What a wonderfully simple way to describe much of our world.  I am reminded of this whenever I see people working on the “energy” problem.  Software people clearly know, that if only we wired everything up and monitored our energy use, the rest of the problem would be trivial.  Economists clearly have the upper hand, because they can describe carbon trading as the sure fire method to reduce carbon output,  increase energy efficiency, and still have economic growth.  Photovoltaic manufacturers, electric car builders, and wind farm developers are among the many queuing up at the public feeding trough.

Nothing wrong with any of those solutions.  Just bear in mind the aphorism.

By the way, our hammer is a whole house fan.