This is yet another insulating window treatment idea.
I've thought about using rigid insulating panels in some of our windows, but we don't like the idea that you lose all the lighting from the window when you do this.
This idea is to use a rigid insulating panel over part of the window, but leave part of the window uncovered to allow light to come in. Sunlight is very bright, so it does not take too large a section left open to allow quite a bit of light in.
The pictures show this panel in one of our windows -- its about 2/3 insulating panel and 1/3 rd window. It still lets in a lot of light.
The 2/3rds insulating panel in place.
I guess an Oak
molding could be used to cap the top of the panel.
You can actually still see out of the window, and it could be made a bit shorter to see better.
I think that as an insulator it probably works well. As long as the fit is tight enough to prevent circulation of air, the air in the space between the window and the insulating board should be stable, as its going to be colder than the room air. I might try a smoke pencil test later to see if there is much movement.
This rigid insulation board cuts nicely with a long bladed utility knife run -- very quick to make.
The insulating board I used is 1 inch Atlas R-Board. I like this stuff because it has a nice face sheet that looks good -- kind of like a sheetrock surface. It could even be painted to match the walls. Its a polyisocyanurate insulation, so the 1 inch is good for about R6.5 plus the R value of two air films -- maybe R 8 altogether -- a lot. A double pane, low-e window with a well fitted insulation panel of this type is approaching the R value of a lot of walls.
Another nice thing about this arrangement is that the insulating shades we have still go up and down nicely with the panel in place. So, at night, you can have even more total R value.
This is the back side of the rigid insulation board.
The back face sheet is the same as the front, and takes paint well
if you want to cover the writting.
Cost of the polyiso panels is about 50 cents per sqft. Using this calculator, the payback period for our area (SW MT, 8000 heating degree days, $2 per gallon propane furnace) is well under half a heating season!
A caution here is that while lots of people use rigid insulation panels, its not a practice that is recommended by the manufacturer because the insulation will burn in a fire. So, as always, do your homework and make your own decision.
Gary December 4, 2009