Back in the late 70's and 80's there was an effort to develop very good insulating window shades. These shades used multiple layers of reflective plastic films to achieve very high R values. Some of the shades were reported to have R values in the R15 area, making them as good as a typical insulated wall, and cutting window heat loss by a factor of 7 over a conventional double glazed window.
With the end of the oil crisis in the 80's, work on these shades stopped, and (as far as I know) the commercial products that were coming out went away.
I think that this is a very promising area for development, and well within the capability of many backyard inventors and experimenters. It is a promising area for both DIY and commercial development.
Heat loss from windows can be as high as 50% of the total house heat loss (depending on the house design), so cutting this to near zero with these shades could be a significant reduction in fuel costs and greenhouse gas emissions.
These shades could improve the performance of passive solar homes by greatly reducing the night heat loss through large, south facing windows. They could also allow larger windows in super insulated homes without incurring additional heat loss penalty.
While inside shutters made from rigid foam board insulation can offer similar R values, these shades made from layers of film have the advantage that they rollup out of the way within the existing window frame. This eliminates the need to find a place to stow large and awkward foam board sheets, and makes deploying the shades much easier.
I've assembled some material below that describes some of the designs, and provides some early test data. These might help you get started on a similar project.
If you do some work on these high R value thermal shades, or have information to add, please let me know -- Gary...
|This excerpt from the William Shurcliff book "Thermal
Shades and Shutters" covers several of the multilayer designs.
Some of which were commercially available.
One example includes 3 transparent layers that can be deployed separately for various winter and summer scenarios. It also has a very tight edge seal design.
A 2nd example uses 5 layers of reflective material to achieve very high R values. All 5 layers roll into a 2 3/4 inch diameter roll.
The third example uses 4 layers of reflective material in a configuration that "self inflates" when down to achieve spacing of the layers. The shade rolls up on a 3 inch diameter roller when deflated.
Ronald Shore, James Gronen
|This article describes some early
experiments on 5 layer thermal shades that self inflate when deployed.
The various materials used for each layer are discussed. Testing that compares the performance of these muli-layer shades to various types of conventional insulation is provided. The performance of the shades was found to be comparable to 4 inches of fiberglass insulation!
I've listed some places that sell reflective film here ...
This is by no means an exhaustive list -- if you look around I'm sure you will find more. If you find a good source. please let me know.
Places that sell Hydroponics growing suppliers may offer thin films that are highly reflective, such as Foylon.
Gary Jan 20, 2008