Based on some of the questions that I have been getting there seems to be some confusion about using window film or clear poly or vinyl plastic sheeting to save energy at windows.
Window Film First
To me window film is the thin reflective film that is applied directly to the window glass. It is the shiny stuff intended to reduce your air conditioning bill in the summer time. It does add a little extra thickness to the window glass so it slows down the heat conducted through the glass a tiny bit. The main reason it is used is to reflect the radiation from the sun away from your windows rather than letting all the heat pass through the clear glass.
It is not intended to help you in the heating season. It is most often used in office buildings because most office buildings need to be air-conditioned all year round. All that heat from office machines, pots of hot coffee and lighting makes a lot of hot air. I think that most of the hot air comes from all the bosses talking at once.
For wintertime, home use the tiny extra thickness helps to slow the heat flowing out through the glass. A little heat radiation is reflected back inside during the heating season but the energy savings is very small.
The main value for reflective insulating window film in the wintertime is to give the sales folks another point to talk about. It may reduce the heat flow through the window by 10%, not a real value for the money. Reflective window film is a good value in the summer on the sunny sides of the house but not so good in the winter.
Plastic Sheeting for Windows
Clear vinyl or polyethylene plastic sheeting, vis-queen, painters drop cloth plastic sheets or similar materials are useful for make shift storm windows on the outside of the house. The thicker the plastic is the better it will hold up to the weather. They are expected to last only one or two heating seasons and are an inexpensive substitute for real storm windows. The stuff sold in kits may be called film because it is thinner than the bulk roll material you buy at your hardware store.
Tape it to the window frame either with clear packaging tape or with ugly duct tape. A neater job can be done using double-sided 3m Scotch Brand tape. Put the tape all around the window frame. Stretch the plastic sheeting flat as you put it on and trim the excess away with a razor knife. Easy, fast and inexpensive. Not so nice for appearance.
Some folks leave the bottom two corners unsealed to allow moisture to escape from the space between the window and the plastic.
Do not use the heat shrink type of clear plastic sheeting on the outside of the windows; it is not made to take the weather.
Do use the heat shrink type of clear plastic sheeting on the inside of the windows. It can make a neat inside storm window. Working from the inside is safer than using a ladder on the second story windows. Again, use the double-sided 3m Scotch Brand tape. It makes a neat job of it and it will peal off cleanly in the spring.
After you tape it in place use a hair dryer to stretch it drum tight with no wrinkles. The heat shrink plastic for indoor use is very clear and stays clear. Easy to use even if you put the job off too long and it is snowing outdoors.
Leave a few inches unsealed by tape at the bottom in a couple of places to allow moisture to escape. If you seal it, completely it will fog up and you may get some interesting frost designs.
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