KSD Solar Windows: New Spin on Low E Glazing
by Lloyd Alter, Toronto 
on 11. 6.07
Here is a neat spin on low-e windows. Normally one picks the kind of Low emittance coatings depending on your local conditions; different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain. It's done by sputtering a coating on one side of the glass inside a sealed double glazed unit. (more tech here)
But what if you live in a temperate climate with hot summers and cold winters? You want to keep out the heat in the summer and let it in during winter. How do you get the best of both worlds?
Dr. Heinz Kunert of KSD Fenster in Germany figured it out in 1990, in one of those slap-upside-the head "why didn't I think of that" simple solutions- he put the glazing in a pivot so it can be rotated to reflect the heat out in summer, inwards during winter. Too bad they have the lamest website ever and no distribution that we can see, all the window manufacturers should have a version of this.::Eco-Logical Innovations or ::KSD Fenster , who make them in the Black Forest. via ::Eco-Geek
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This is a brilliant solution for generally south facing windows.
However, for generally north facing or building shaded windows the added expense would be completely unnecessary.
For south facing windows there are combined solar gain and heat loss controlling windows that approach the 60% effectiveness mark, respectively. If one has only a relatively small square footage in that southerly exposure and especially if the room is isolated from the rest of the floor area- like a bedroom or recreation room seldom used during daylight hours for example - then one of these multi-coated, non-rotating windows would be the ideal solution.
I see the rotater being the perfect solution for a home office or kitchen.
Small Problem with this solution, There is no such thing as a one way heat coating. It violates the second law of thermodynamics. Google Maxwell's Demon. It will make no difference which way this window is turned.
LA there is no violation, it is a mirror.
The previous website hasn't been updated since 2004. I feel like LED technology has gotten better since then. I feel relatively comfortable with my LED lights.
Another way to control sunlight seasonally, which is very economical (under $40), is by using static cling (non-adhesive) window film. They claim to block 95%-99% of UV rays and provide a bit of insulation through the vinyl thickness (usually about 8 mil). In one article that I read, the author summised that the temperature inside was about 4 degrees cooler in the summer with the film. (Don't recall that being a scientific study, just his feeling.) For the summer, that could be a significant energy savings.
Other companies claim that the film helps keep in heat during the winter. Not sure exactly what they mean. Blocks out sunlight heat but keeps in furnace heat??? If so, not sure that would be a good tradeoff. Unless you kept the film off during the day while sunlight was coming in, then applied the film after sun goes down to retain that heat indoors. (It actually is that easy to apply and take down, so that would be possible, albeit a bit inconvenient.) Would be a good experiment.
If you buy the non-adhesive, static cling kind, you can reuse it -- if you reapply it to the backing or some other surface to keep it from shrinking.
Most that I have seen are of the decorative variety (faux etched glass, frosted, or stained glass). I know of only 1 company, Artscape, who sells completely clear non-adhesive. HomeDepot carries their products, or you could go to their website for more info. Here is their website info on the clear:
Summer / Winter Insulating Film
Saves up to 12-18% of Annual Energy Costs
99% UV Rejection,
85% Light Transmission,
65% Solar Heat Rejection
Easy Application without Adhesives
MFG Model # : 01-0119
MFG Part # : 01-0119
Price: $34.98 (48" x 84" roll)
But, do keep this stuff out of the landfill, it is made of PVC vinyl.
Greta
AmericaTheGreen.org
Disclaimer: I do not work, nor have I ever worked, for Artscape or Home Depot. I have done some web work for another decorative window film company, so I am pretty familiar with this product.
That really doesn't look like a very efficient system. Anytime you add in a point of motion like that in a window, you're creating a thermal leak. My suspicion would be that the overall R-value of the window would actually be reduced by having this "spinner" built in, perhaps significantly.
my house has 6 gigantic south facing windows. Granted they are from the 70's but in the dead of winter -30 celcius, if its a sunny day outside it will be 27 celcius inside. I cant wait to replace them with solar gain windows as i may be able to heat the house for much longer cause the new windows wont leak like the old ones.
Anyway by far the best way is to get solar gain for south facing, insulating for non south facing and get some form of window cover for the summer.
The angle of the sun will also work to your benefit as in the winter the sun will be low and will get well into the house, in the summer the sun is high and for the most part very little light will enter.
apart from all the other downfalls already explained in the comments there is very little need for such a window, nothing a window cover wont do.