finance

We’re in Sunset Magazine!

Sunset Magazine July 2015Exciting news! AirScape has been mentioned in the July, 2015 issue of Sunset Magazine.

Matt Golden, an efficiency expert, provided some tips to help readers efficiently keep their homes cool through the summer. In addition to sealing HVAC ducts, properly insulating the home, and drawing the blinds during the day, Matt recommended homeowners invest in a whole house fan—a suggestion we obviously agree strongly with, especially when ours is the brand being recommended.

Sunset’s July, 2015 issue is on newsstands now. It’d be ungrateful for us not to suggest you go out and get a copy, so, if you’re not already a subscriber, please do! We’re a little too excited, however, not to provide a link, so you can also check out our brief appearance here.

Also, Matt is the CEO of a very cool start-up, Open Energy Efficiency. Be sure to check out their website as well!

Now Introducing… Solar-powered Whole House Fans!

Not really. The headline above is a little tongue-in-cheek. Readers of this blog will know our fans are designed to be run at night, when cool outdoor temperatures can be drawn indoors. Since photovoltaic cells can’t generate electricity at night, directly powering a whole house fan with solar generated electricity isn’t possible—unless, of course, one wants to run their fan during the day, which would heat the home rather than cool it!

We do, however, frequently receive calls from homeowners wanting to know if they can run a whole house fan directly off of their home solar array. We wish they could. Because they’re a more efficient substitute for mechanical air conditioning, whole house fans greatly compliment solar by reducing the size of array needed to provide the same cooling. But again, photovoltaics don’t work at night.

To operate a whole house fan with electricity generated by a solar array, homeowners need some sort of energy storage device that would allow them to store electricity they generate but do not use during the day. Then, this stored electricity could be drawn down through the night to power the whole house fan.

In short, they need a battery—which is why we’ve followed Tesla’s recent announcement of their new Powerwall home battery system with great interest. Home battery systems have been available for some time now. But they have never been as prominent in the popular discourse as they are now, makings this the ideal moment for a blog post “back of the envelope” analysis about using a home battery to operate an AirScape fan.

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cheapest way to reduce co2

We have (at least) two huge problems facing us.

  • Climate Change (too much CO2 is being emitted)

  • No Money (we’re all in debt)

Logically, we should spend our limited resources to the best effect. So, what is the best bang for our buck ? The parameter to measure is Tons of Carbon Dioxide (avoided) per Dollar…. the lower the better. So, here are a few of the common things we can do to reduce energy usage.  The spreadsheet shows most of the calculations (contact me if you want to know more details), but what is missing is the usual energy savings return on investment. This figure is all about environmental good. It just so happens that environmental good is good for your pocketbook.

So, please let’s spend our money wisely. Hint: Electric cars are cool (not as cool as pluggable hybrids), but they are not the best way to spend our money if we want to reduce carbon dioxide.

* There are many other energy and carbon dioxide reducing strategies not mentioned here.

financial value of green

How much do ‘eco improvements’ such as whole house fans add to the value of your real estate? With a little bit of math, and some financial formulas, we can figure that out. Here is an example of a homeowner who installs one of our 4.4e WHF models. Let’s take a conservative value for energy savings ($500 per year), with a desired return on investment of 8% (you could not get that anywhere else..). What we do is use the financial formulas to figure how much money would need to be invested at 8% interest in order to return $500 per year, over the life of the whole house fan. At the end of the 20 year life span, we assume (also conservatively), that the WHF has no remaining  value.

Plugging in the numbers: i = 0.08; n = 20; Savings per Year = $500, yields Present Value = $4909.

Wow! That means that if you paid up to $4,909 the return on investment would be 8%. (we don’t charge that much for the 4.4e…)

Saving Energy is a damned good investment. Who woulda thunk ?

First pass on energy savings

We’re getting ourselves ready to build some software to help predict whole house fan energy savings. In the meantime, I put together this spreadsheet, which I think is a pretty good approximation for the coastal areas of California.

Potential Whole House Fan Energy Savings per Year for California





Input Energy cost arrow $0.24 Dollars per KWH
Application High Speed Watts Low Speed Watts Energy Savings * (per Year)
2.5WHF 288 250 $777.89
2.5eWHF 200 43 $826.70
Air Conditioning 2808 na $0
* Assumptions are that the cooling season is 5 months, the WHF is run 10 hours/day, 40% use is at low speed, an average deltaT at night is 10º , and that all WHF cooling offsets AC use.