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Aluminized Mylar Window Treatment

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Posted by Gary on August 1, 2005, 8:07 pm

We have large, east facing windows that gain way to much heat on
summer mornings.  They also lose way to much heat in the winter.
The windows are lightly tinted, and during the heavy sunshine period,
we lower a set of the cellular blinds to reduce heat gain, but my
feeling is that there is still a lot of heat gain.

We are thinking about adding a 2nd shade between the window and the
existing shade.  The 2nd shade would be a roll up type, and would be
made from aluminized mylar -- reflective on both sides.

My hope is that in the summer, the highly reflective surface will
reflect most of the light of all wavelengths right back out the glass.
  And, while it won't be as effective as blocking the light outside
the window, it might be pretty good.

Dr. Shurcliff's book on on "Thermal Shutter and Shades" says the
aluminum foil can be very effective in the winter as long as it has
some air film space on each side.  He says:

"Foil flanked on both faces with a thick region of still air is worth
R 2.7!! (exclamation points are mine).

This high performance, he says, is due to the foils ability to reflect
IR radiated from heated objects back into the room on the inside
surface, and the fact that it radiates almost no energy on the outside
surface due to its low emissivity.

I plan to install wood strips on the sides of the window frame that
the edges of the foil will lightly rest against for a seal, and to
have a slightly weighted bar along the bottom where the shade rests on
the window sill to seal the bottom.

This all seems like a pretty nice, and inexpensive way to go.

Has anyone tried this?
Does anyone see any down side?



"Build It Yourself" Solar Projects

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Posted by dances_with_barkadas on August 16, 2005, 1:42 pm
Here's an idea.   During a week (8 hours), keep a log of how many
seconds you spent looking out the window..  Divide by 168x60x60.

Then tell me if you shouldn't just put R-10 fiberglass over the windows

Posted by Gary on August 16, 2005, 3:59 pm
 dances_with_barkadas@yahoo.com wrote:

Actually we look out the windows all the time -- its a great mountain
I'd never give up the daytime view, and putting R10 panels in and out
each night is too much work.



"Build It Yourself" Solar Projects

Posted by nicksanspam on August 16, 2005, 5:38 pm

How often do you look out at night? How about an insulated wall between
the low-mass sunspace with lots of south windows and the living space?


Posted by Gary on August 17, 2005, 12:31 am
 nicksanspam@ece.villanova.edu wrote:

Hi Nick,

Rarely -- it would be easy to give up the night view.

How about an insulated wall between

I'm a bit lost here.
Could you explain that in more detail.

My offending big windows face just a touch north of east.  They get
too much summer sun (7am->11am), but basically zero winter sun (this
is due to the mountains to the east, and the lower and more southerly
winter sun). The way my house is built, the south exposure is hard to
take advantage of -- the garage takes up half of it, and the way the
rooms are arranged makes it hard to use the other half even if I was
willing to do major wall surgery (which I am :-)).  I have made some
use of the garage part of the south exposure with this:
But, I am hard put to find any way other than active collectors on the
south roof (which I am thinking seriously about) to use the rest of
the south exposure.
 From a passive solar point of view the house design stinks, and I
would not have built the house this way, but it is the way it is, and
aside from the bad solar design we like it a lot.

I guess one possibility would be to build a low mass sunspace south
from the half south wall of the house not used by the garage, but
getting the heat from the sunspace to where its needed, and providing
some type of heat storage seem like difficult problems?

If there is a better way, especially one that would allow more solar
gain without the complexity of an active collector system, I'm all ears.

The aluminized mylar window shades seem like an easy way to 1) cut
down on the unwanted solar gain in the summer, and 2) reduce the heat
loss in the winter.


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