Windows pose a problem. Single paned, aluminum framed windows allow heat to pass through or out of your home, so how can you stop this loss of energy?
After the home inspection, I am sitting in the living room with the owner. The conversation has turned towards steps that can be taken to lower a utility bill. He had noticed that I was writing notes when examining some items, and he had wondered why, so the idea of improving the home developed. He was quite handy with many tools available to him. To me, one factor was striking: we were sitting in a room that was only lit by incandescent lamps, since the windows were covered with blankets. This was done to lower his electricity bill, but this is not my favorite solution for a window.
Window Curtains as Insulation
Installing a heavy fabric as a curtain can be a way to insulate a window. I think a proper curtain is better than a blanket in appearance, but I often see renters using blankets over their windows. However, this is a trade off. Lighting a home with natural light is more energy efficient than using a bulb, especially an incandescent bulb. Heavy curtains do fit in with more clasic decors. Adding a backing to this heavy fabric can help perserve the fabric from damage by the sun, and further insulate the window space. I am not convinced that living in the dark is healthy or energy efficient (the skin needs eposure to natural light to produce vitamin D).
Is there a better window covering to help insulate? Wood shutters are good at this task, yet again you will loose the light. I have wood shutters on my office window. I do keep them closed on colder, dark days, where I would be using artificial light anyway. My hope in my own home is to avoid turning on an appliance when a natural means would suffice. Wood shutters can be expensive. Even plastic shutters can be costly when installing them on every window. For me, there is a window shade that I would love to install on my own windows. The honey-combed window curtains/blinds have a good insulating factor. The air caught between the fabrics of the blind acts las an insulator. What I do appreciate about this blind is that it can be made from a lighter colored fabric, which allows a diffused light into the room. However there is a way to permit light to enter, while blocking the main rays. Instead of having a blind which only goes from the top down, there are blinds where you can adjust the position of the blind. The top of the window could be open to the light, while the lower portion is blocking the stronger sun. Yes, these blinds are more costly than standard ones, but they are better in price than shutters.
Having bamboo shades on the inside can also help insulate a home.
How Many Panes of Glass
Quite a few homes were built with windows made from single panes of glass and aluminum frames. These are poorly designed if you are thinking about energy efficiency. Heat can pass through that glass easily, and the aluminum has a problem with thermal bridging (conducting heat through the material). Newer window designs have two or three panes of glass. Air can be between the panes, which is fine, but some window units contain gases such as argon, which can be better insulators.The framing for these windows will have metal clad with a material like vinyl to slow down thermal bridging. If you retrofit your windows, you will notice an immediate effect in your utility usage.
I have not looked for these at home improvement centers, but I have seen them on home inspections: a window which fits over your existing window. This frame is designed to be attached to the exterior wall. You would remove your current window screen when installing. To open your window, you have to open your old window, then the new window. If you take the time to seal the new exterior window, you can have the same insulating effect as a double paned window. There is a company which has developed a simpler method to create a second pane. They apply a magnetic strip to the exisitng frame. The new pane is in its own frame with a magentic strip. The magnets create a seal, but you can still pull them apart for cleaning or repairs. This method does look a little better to my mind than the exterior frame, and you do not have to open two windows.
I have seen homeowners use plexiglass as a second pane. Plexiglass is a good material for a do it yourself project. It can be cut with a saw; it is not costly; and the material can take some abuse from storms. However, most people place this directly onto the exisitng glass, with the thought that thicker means better insulation. An air gap is better for this purpose. A plastic strip can create the gap, and then you need silicone for a window for the installation. To make this plexiglass appear better, you do have to take time with the installation. Use the silicone sparingly. Plexiglass will look differently from glass over time, so that is a downside; however, this project can help some till they can afford new windows.
If you are replacing windows, remember to recycle the old units. Obviously, the newer, more expensive options are the most energy efficient windows.This is not always a practical option financially, yet other methods are available. Recently I began work on framing awnings for my windows. Awnings block the heat while allowing some light.