Bottom-Up Insulating Shades for Light and Insulation -- Our R8.3 Window

The Half Shutter idea, which provides both good window insulation and also allows daylight through the window into the room got us to wondering if the same thing could be accomplished with a thermal shade.  Here is a first cut at trying a top-down/bottom-up shade with side tracks to provide some view, some day lighting, and some insulation.  The nice thing about the thermal shade is that it gives a nicer look than the Half Shutter.

top down insulating shades
The shade in the part up mode that allows views and light but does
some insulating on the bottom -- normally it would be up further than this.

The idea is that when you pull the shade up from the bottom,  it still insulates the bottom part of the window well (like a Half Shutter), but it allows both daylight and views out the top part.  It still insulates because the glazing cools the air between the shade and the window, and that pocket of cool air is stable.  If the shade is pulled over part of the window from the top down, the air cooled by the glazing simply sinks down along the glazing and pulls in warm air from the room -- so, the insulating value of the shade is lost unless the shade is lowered all the way to the bottom.

This shade was also purchased with side tracks (see below) to improve the thermal performance by reducing air leakage on the sides.

This window also already has a double Mylar inside storm window -- so clear you can't even see it in the pictures!

This window is a bit more challenging because it has the triangle top.  To allow the use of a regular shade, I added a horizontal board just at the bottom of the triangle to support the shade. 

The pictures just below show how the top-down/bottom-up shades work.

no shade
Shade fully up.
top down
From the bottom up for daylight, view and
insulation.  Ideally further up than this
picture shows.
bottom up
From the top down -- not sure what
one would use this for.
full shade
Full shade.

Side Tracks 

This shade has side tracks that reduce the leakage air around the sides of the shade. 

window side tracks
The side track to reduce air leakage.
window insulating side tracks
side track closeup
Close-up showing how track engages
the shade.  The shade fabric has
a similar notch all the way down.

The pictures above show the side tracks.  The shades have a notch cut out of the edge of the shade which engages the T shaped track that mounts on the window frame (see right picture above).

The middle picture also shows the added support board that the window shade is supported by, and the frame for the double Mylar inside storm window.

The claim from Symphony Shades is that the double cell shades with the side tracks add about R3.3 to the window R value.  While I do not have any independent way to verify this value, it does seem about right given the construction of the shade and the track.  For a regular double pane window (which has an R value around 2), this should cut the heat loss to about 40% of what it was with just the window.

So, the total R value for this window is about:  R3 for the low-e double glazed window + R2 for the double Mylar inside storm window + R3.3 for the new shade with side tracks -- for a total of R8.3!

Using the Insulation Upgrade Calculator, the saving for us is about $31 per year, or $492 for 10 years with 10% per year fuel price increase.  Your saving may be better or worse depending on your climate and the windows you have.  Since most people will want to have curtains or shades of some type anyway, the only added cost is to select shades that insulate better and have the side tracks.   Thermal shades may also qualify for federal and/or state rebates.

shade support
This shows the new support board for the shade being added.


We have a similar set of kitchen windows with triangular tops and a set of old shades that has zero insulating value.  We are thinking about using the same sort of top-down/bottom-up approach on these windows.  The fuel saving will be about $100 per year for the larger area.

insulating windows
The kitchen windows that are candidates for the top-down/bottom-up insulating shades.

Gary November 11, 2011