I know that double-glased windows are known for their insulating properties. When I was a kid in Japan my mom put plastic sheeting over the windows of our kerosene-heated house. The guy I bought my house from also put iron-on plastic sheeting over the windows leaving about a one-half inch gap between the plastic and the glass. I wonder if I can take off the sheeting and put up a pane of glass instead? Can it be any kind of glass? Or does it have to be a special insulating glass?
It’s actually not the glass itself that is the effective insulator, but the layer of air trapped between (which is why thin plastic sheets work as well as they do). I would think you could use any type of glass or plastic as long as it traps air between it and the window.
Around here they are called “Storm Windows”. Usually you can buy them premade to cover any size window.
Not only is glass not the effective insulator, it’s not really effective at all. Ever put your hand up against a window when it’s cold out. The glass get’s pretty cold, and if there’s a breeze in the room (say central heating duct), the circulation is going to carry the cold into the room (well, it’s going to absorb the heat from the furnace and …nevermind).
Without seeing you’re windows or how you intend to put this up and take it down (and store it when not in use), you may be better off with plexiglass as it’s much lighter and more durable then glass.
You can get glass specially designed for double glazing . This is supposed to have better thermal qualities compared to “normal” glass. Here is a quote from one one manufacturer:-
*Pilkington manufactures a range of low-E glasses, using both hard and soft coat technology.
Pilkington K Glass, the market leader, incorporates hard coat technology to produce a highly durable thermally efficient coating, whereas the soft coat alternative, Pilkington Optitherm SN, can be used to further reduce heat loss from glazed areas and is particularly ideal for large-scale curtain walling applications and other commercial projects.
Both products provide excellent thermal insulation and greater comfort for the majority of environments.*
The air gap is the real insulator, and it’s an elementary heat transfer problem to work out the ideal gap size for a given situation. Too small, and the air gap doesn’t provide much barrier to conduction. Too large, natural convection cells will be set up which provide efficient heat transfer between the two sides.
You sure can. The outside doors in my 75 year old house had single pane windows in them, and leaked heat like crazy. I took the glass out and re-routed the opening to accommodate 2 panes with a half inch space between. Once I had the glass, the whole project took all of a couple hours to finish. There are no longer rivers of ice flowing from the front entryway to my diningroom every winter.
Regular old glass works fine for this, you don’t need any special insulating variety. It’s the dead air-space that provides the insulation, so you do want 1/2" or so between panes. If the spacing gets too wide though, you can get convection currents going. That heat transfer mechanism defeats the purpose of double paning.