Solar heat from black window shade

[Jim_Rogers]

Have any of you guys tried this black window shade thing?

I have read about it on another site.

It seems that you take down your regular roll up window shade and put in a wooden frame that has a piece of black plastic hooked to it.
You leave an opening at the top and a small opening at the bottom and when the sun hits the black plastic it heats up the air and it flows naturally up and out the top opening.

I was thinking that this year I'd try it in two or three windows I have in my house that are facing the morning sun.

Jim Rogers

[Ianab]

I'm sure it would capture the heat from the sun, and that warm air would come out the gap at the top. But I'm not sure that it would capture any more heat than just letting the sun come in and warm up the floor / carpet / cat / your feet, or whatever else it happened to shine on? The amount of energy coming in the window, and into the room, is the same either way.

Ian

[sprucebunny]

In addition to what Ian said, the heat trapped close to the glass may damage the seal in double glass windows.
The ones that face the sun have been the first to go in my whole house of defective windows. The manufacturer replaced all the sash once and have managed to go out of business before the second set lost their seal :

[Thehardway]

Like Ian said, there is a question as to whether or not just letting the sun in, would provide more or less heating.  This depends on the absorption and thermal mass of the materials the sun would normally shine on, through the same window.  If you have a dark colored masonry floor, the shade would be a bad idea as you already have a superior absorber and thermal mass, if the sun is just striking a large peice of light colored upholstered furniture, the blind might be a good option. Also keep in mind that you may offset the energy gained in heat by having to use artificial light.  This would be a 0 energy gain scenario if you turn on lights to get more heat.

There is an additional step I have seen using this general idea. It is made and commercially distributed under the Inflector brand but it uses a perforated material that is a black carbon coating on one side for absorption with a metallized film reflector on the other which is silver colored. The blind is reversed based on heating or cooling mode.  The degree of perforation determine how much heat is reflected or absorbed and how much sunlight is allowed to pass.  I have a sample of the material and it is interesting stuff but not terrible pleasing to look at. They reportedly limit heat loss through the windows by reflecting heat back inward with the silver side in the winter.

I have a large, south facing window in the gable end of my house.  I hung a large steel chandelier with flat black paint on it in the window. During the winter months it heats up and works like a giant radiator warming a portion of the room.  In the summer, the gable overhangs keep the suns higher angle from hitting it so it stays relatively cool.

A large dark colored rug on the floor where the sun hits is also a good way of absorbing heat.

[Jim_Rogers]

I haven't discussed this idea with my wife yet. But I'm about to.
The two windows I want to try are in a side room off the living room where my daughter's computer is. These shades are never open. One is even duct taped shut.
Wife doesn't want anyone passing by the street to be able to look in and see my daughter sitting at the computer. This is the street side of the house as we are on a corner with a dead end street.



 

That side of the house is the east side.

I am also thinking about doing the two or three windows in the front room so that we'd have three windows on the east side and two on the south side. Maybe even do some of the upstairs windows.

We'll have to see if she likes the idea or not.

Jim Rogers

[Ianab]

If the shades are drawn all the time, then the idea would have more merit.

I wonder if a little fan and maybe a vent to open and close? When the sun is shining, and you want the warmth, open the vent, turn on the fan. At night, shut it up to keep the heat in?

Sort of like the collector on a solar kiln.

Ian