Is there a significant benefit to using plastic window insulation year round?

Question

In order to help save more money and funnel more of those savings to debts, I'm looking for more ways to save money.

I've heard that puting plastic window insulation over single-pane windows typically found in older houses can reduce utility bills by up to 50%.

But I'm wondering, it's February, and I'm in Portland, Oregon, USA. Summers can get as hot as 100 degrees fahrenheit in the extremes. Living in a temperate climate, is there an advantage to keeping the plastic up year round, or will I just need to remove it in the Spring/Summer?

To further clarify and address the "airing out the house" issue, let's say that I only open two windows upstairs and two windows downstairs. There are 14 windows total in the house, plus 1 door upstairs and two doors downstairs, one in the front and one in the back.

My motivation for asking is to determine if the inputs I put in now in the form of putting up all that plastic in February will pay any dividends, or if it's best I wait until October.

Answer 1

If the plastic reduces air exchange between your home and the outside world in the wintertime, it will do the same thing for you in the summertime. You will get some benefit from the plastic in the summertime. I can't tell you how large of a benefit. But, based on my own experience, the tape that holds the plastic in place tends to grow loose after a season or two, so the quality of seal will deteriorate and you may find yourself having to put new plastic up anyway to maintain the seal.

Also, in my home (1921 with single pane windows) the impact of the plastic could not really be measured in terms of utility bills. It was nowhere near 50%. You will probably find that it makes the room much more comfortable, though.

Answer 2

The plastic will help you in the winter, but it's pretty much useless in the summer. Sunlight on the roof and coming through windows is a far bigger issue than heat exchange in the summer (45-55% of the cooling load in air-conditioned homes) and window plastic won't help with that. It will help stop air leaks, but you can do that with cheap caulk and weatherstripping without sacrificing the ability to open the windows. In the summer, you'll be better off putting up cheap awnings to shade south-facing windows. Save the plastic for next winter.

As for the plastic's effect on utility bills, I don't see how it could cut your total costs by 50% unless every part of the house but the windows is absolutely perfect. It might cut your window-related costs by 50% in winter, but windows are far from the only source of energy waste in any home. The walls, floors, and ceiling probably account for more air leakage than the windows, although those leaks are usually not as obvious.

Answer 3

I lived in an old apartment building with horribly drafty single pane windows. They were all 3x5 except the kitchen window over the sink. Using the Duck Brand window shrink film kit saved me a LOT of money on my winter utility bills. I lived in Eastern NC at the time. My electric bill would hit $300 for a 750 square foot apartment in the winter time, not to mention there was no wall-to-wall carpeting. The landlord was cheap and so they used stone/ceramic tiles in all rooms except the bedrooms.

There were two bedrooms and they had linoleum flooring. I lived in the bottom of two floors and so my heat would escape through the floor and above into the apt above me, as well as out the windows. The $300 bill was before the shrink film was put up. There was also no central a/c. I had a window unit which allowed more escape of air. I took care to completely close off the a/c unit and cover the entire window with shrink film.

My bills for winter time never went above $100 after that. It was only me and my toddler daughter living there.

I'm in another old apartment in mid-state SC. My a/c has been cranking all summer because I have large bay windows and the building is from 1949. I can feel hot air coming in around the sill. I ordered a window kit today to apply because my last bill ending 8/31 was $117. There is no way I can afford these high costs and also it will get far worse in winter.

I left my window film up year round in my old apt and I'm telling you, it saved me hundreds. Like I said, $100 bill total or less in winter (Nov-Mar) and $65 or less in spring and summer. Here we have to run a/c until mid October in SC as it is still too hot. My windows don't open in this apt but I do have a back door so I can open that to swap out air.

In short I'm saying you can leave it up year-round. I did until I moved and I just moved here to this other place but once this film goes up this weekend, it will stay up until I move out. I tried to get my neighbor at my last building in NC to do her windows but she was too lazy. I even offered to do them for her because she kept complaining about the $300+ electric bill. My parents live in a 2536 square foot home and their bill isn't even $300 in winter or summer! No way I'm going to pay that for a 950 square foot place.

Put carpeting down if you can, or at least area rugs, which I did at my old place with the ceramic tile. In winter that tile was like a block of ice under bare feet. And make sure the weather stripping around the doors is good. I can't do anything about the walls or the attic, as I don't own this place (though the landlord offered to sell me this condo)...not sure I want such a money pit, though it is nicely remodeled inside. These things I can tell you truly help.

Put up the window film. Replace the film as necessary. I promise you it works year-round. I'm cold-natured, and so I notice a huge difference in winter and also summer...my a/c would be on every 5 minutes and at times it wouldn't ever cut off at 74 degrees. My condo is in full sun and facing the south.

I keep the a/c thermostat at 74 at night in summer unless it's 95 at night. Then I will put it on 73. In winter I usually keep it at 73 all the time unless I leave on vacation. Then I put it on 65. I can't wait to move out of this place and be done with apts and condos for good.

They are such rip-offs with the cheap flooring, and old sub-par or cheap windows and insulation. I literally lived in a $1200 a month apt in a gated community once, and one of the windows had a huge gaping area along one sill. How they charge that kind of money and skimp on materials is beyond me. I will never willingly live in anything but a brick and mortar singke family home after my lease is up here.

I use light-blocking and energy saving curtains and blinds on all windows. There are only 3 in this condo, but 2 large bay windows (65 inches wide) are facing the sun. If I didn't have the blinds and curtains up, the sun will blind you by midday. I keep the curtains and blinds closed all the time in summer and I open them in winter to allow natural sunlight to warm the rooms. Buy white vinyl or bamboo blinds. White reflects light and heat.

These curtains, blinds, and shrink film should add up to about a 50% savings if not more. I definitely saved 30-60% on bills at my last place.

I take care to cut the film large enough to fit over the molding (about 1" from the outer edge before it meets the wall), and I do use the blow dryer to reduce the plastic whipping in the wind when strong drafts come through. I also place it beneath the blinds so I can open them if needed.

Answer 4

Single pane windows are horribly inefficient. Having the plastic up will pay dividends for the remainder of the winter and if you use AC in the summer it will help there as well. As for airing out the house when its a nice day, you could just remove the film from a couple windows to get the airflow going.

Answer 5

Yes! People will think you are a shut-in.

• Solicitors will not come to your door, thereby less drafts.

Yes! People will think you are growing something or hiding illegal activities.

• Neighbors will gossip, about drug activity, maybe even mention things to police - free security.

Any possible thing you put in front of your window is going to keep the outdoor temperature from coming in. Aluminum foil, plastic, trash, bookcase, whatever. Some will do a better job than others. Some will do so while making your window usable like weatherproofing strips. Others make it almost completely non-functional - like plastic. What is the R value in your plastic - well that depends on how thick the plastic is, what its made of, and the tape job around it. Will your energy bills be less - Yes. Whatever you put up will make your energy bill less. Maybe a few pennies a year maybe a few hundred dollars. Maybe the body heat produced thinking about this and putting up the plastic saved more than the plastic itself. I seriously doubt 50% unless you had some very drafty windows.

Answer 6

I live in Phoenix, Arizona. Our summer temperatures average around 112 to 115 degrees and many times a lot higher. Typically, our air conditioner goes on from April or May and off at the end of October or early November. I built inexpensive wood frames (imagine a picture frame without the picture inside it) and then installed the shrink wrap over them and then setting them up against the window. That way I could easily take them down and set them aside if I wanted to open the window. The rooms in my house that get the most sun exposure went from being hot to warm. The first year I was there without the shrink wrap my summer electric bill was around $500. After building my window frames and putting the shrink wrap on, the next year I had a $300 electric bill. I am totally convinced that they are well worth investing in.

Answer 7

Starting with the assumption of 50% savings, the implication to me is that the windows are very leaky - letting a lot of air pass. That's because even a new window with insulated glass would not be expected to make that big of an impact based solely on the insulation value of the glass assembly or, in this case, the insulating plastic does not add that much to the insulating properties window. Sealing the places where air leaks through the window assembly would have a bigger effect. (By the way, you'll notice on the site to which you linked, that part of the promotion is that this product can help stop air leaks). The plastic film could be installed over the entire window all the way to the surrounding trim or even the wall and that would prevent air from passing in and out of the house. But there is a better way. Depending on your specific window, you should be able to find various types of weatherstripping materials that allow the windows to operate normally and can stay in place for years. That would be well worth the effort. If you like, tell us more about your particular windows.

Answer 8

I've found that the plastic for old windows in the winter saves about 30% percent on heating costs. The plastic in the summer may help somewhat but weather stripping boosts the plastic's effect in the winter and allows you to open windows in the summer.

I would most recommend weatherstripping for the summer because natural cooling can save a bundle! I use thermal window coverings (curtains) to keep heat down in the day and open windows after sundown and close them at sunrise. Our house has no AC (and we've bought no window AC's) yet it stays about 70-76 degrees all summer (which is crazy now that it's July).

Answer 9

I genuinely feel that placing plastic, of which any kind that involves the double sided tape reduces your air leakage via any window. Our town home is only 8 years old but the drafts are amazing since we are high up on a hill. Sitting at the bottom of the staircase it is quite evident with the air flow. I very tediously cut the plastic a bit bigger than the area I'm trying to cover to alleviate any spaces. Then blow dry it to secure it more firmly. I believe this method works and we save 20% on our hearing costs thru the winter months. Make certain your windows are shut right and locked and purchasing a layered curtain deals the deal. I use the plastic under the blinds also so I can still manage the light during the daytime with use of the sunlight. Good luck in your plastic adventure. Any box of plastic is useful!

Answer 10

The problem with retaining the plastic in summer is that it keeps you from opening the windows and taking advantage of the natural cooling often available at night or on cooler days.

If you're never going to open those windows (I almost never open the ones onto my porch), there's no harm done in leaving the plastic up; it may or may not survive until/through next heating season depending on many factors from humidity to how clean the surfaces were before you installed the double-stick tape.

I do use the window film on my old windows. I'd somewhat prefer interior storm windows, for the sake of elegance, of being able to open and re-close without having to go through the whole heat-shrinking routine again, and because they'd work MUCH better on the bay window. But I haven't been willing to make that investment yet.

Answer 11

It depends--if it gets hot enough inside during summer, you'll want all the ventilation you can get (I assume you have no AC and mostly don't need it). In a 2-story house, I'd imagine that on sunny summer days (however rare those might be in Portland) the upstairs would get hot enough that you'd want all windows open.

In San Francisco, in a lower-floor apartment, I only needed to open windows (any windows) on 1 or 2 days a year, and never needed to open all of them. I had plastic film over 1 window for several years with no obvious breach of the seal. I imagine the surface you're sealing to matters quite a bit regarding longevity though.

Answer 12

I have a similar concern about using the plastic during the summer. This past winter I decided to try the Duck Brand Tape "Cristal Clear Shrink Film" at the beginning of December. The kit was for a 10 window install with 2 rolls of the sticky tape and sold at Walmart for nine dollars & change.; How could I go wrong? So I did it. WOW!! I have to say this shrink film is amazing. I live in a 2 story townhouse type dwelling "I am first floor" and my neighbor upstairs has the exact floor plan, number of windows & doors, and the benefit of sunlight on the roof. We compared gas bills.. For January mine was $59.00, and hers was $130.00. Pretty amazing huh? So with that in mind, I am also thinking about keeping it up all summer. I have central air and am the type to start it June 1st, and not shut it off till Oct 1st. The only thing I did not cover was a single kitchen window to allow escape of cooking smoke if needed. But I don't get strong windows on that side of the house either. Spring in Philadelphia is SHORT to say the least. It goes from cold to having 2 nice days, than straight to hot. So what can it hurt. If it begins to peal from the heat of the July sun, I'll pull it down. I am only out $9.00, but if it has the same effect on my central air bill as it did on my gas heating bill, I am way ahead! By the way, the gas bill amount I spoke of earlier also includes the stove, hot water heater and the dryer. What I did not mention yet is that I am also a renter as you are. One thing you CAN & MUST DO, is invest a couple bucks in a programmable thermostat "placing the landlords safely aside somewhere, and install it ASAP. A good programmable thermostat can reduce cost by 30% just on their own. I did exactly that and have it set very low over night as recommended. Between the film and the lower temperatures at night, my gas bill was $71.00 LESS than the upstairs unit. But for you at this point, you might as well just wait till next November and try the Duck Brand shrink film, than leave it up till it (if it) peals off.

Answer 13

I have a very very leaky house with single pane windows. My great idea is to put the plastic onto my screens. Easy up, easy down. I have even used Saran Wrap and duct tape to get the job done. This just adds a layer of warmer air between the cold and the house. I also put bubble wrap or styrofoam from meat containers between the window and the sill. Just open the window, lay the cut to size bubble wrap down and tightly close the window. keeps a LOT of air flow out. This year I'm doing a layer of thicker plastic on the screens and using the Saran and duct tape method inside... that double sided tape and shrink wrap destroyed the paint on my sills. I use white duct tape right at the panes to keep it from showing as bad. Too hot in ATL for screens in summer and too much pollen in the spring so this is a great use for them!

Good luck everyone!

Answer 14

Air Loss

By far, air exchange with the outside is the biggest factor in keeping the inside a different temperature from the outside.

You can have a 10ft by 10ft (100 sq ft) wall of single pane glass with ice on the inside of it and there won't be as much difference as having a couple of 6 inch holes to the outside.

The reason is that cold air is denser than hot air. The pressure of cold outside air will cause it to come in the lowest air gaps in the house while the hot air escapes through the highest gaps.

If you live in a two story building, and there is an opening from the first to the second story, like a stairwell, there will be a great deal more pressure difference and the cold air will tend to fill up the bottom floor while the hot air will go upstairs and escape. This is one reason it's easier to heat higher floors and harder to cool them.

Of course, we don't usually have 100 sq ft glass panes or 6in holes to the outside. But if you go around and add up all the glass and all the gaps in, you might find a similar ratio.

Thermal Conduction

The surfaces of the building, including the glass all have some conduction of heat energy. Walls and ceilings and even floors tend to be insulated at least a little. Newer construction has far more insulation than older construction. It's usually so much that adding more is almost a waste of energy to construct the extra material and increase the thickness of the walls etc.

Older buildings on the other hand were often built when sources of heat were cheaper and insulation materials either unknown, or simply too expensive. Many older buildings were built with no insulation at all. There is an exterior wall surface, an air gap between studs, and an interior wall surface. There is some insulation value here thanks to the materials of the walls and the air gap, but it's quite low, and there can be a significant loss of energy through the walls just by conduction.

The windows on newer buildings tend to be sealed against air exchange better, and are usually double pane with an air gap, or better in colder climates.

Older houses were often tighter against air exchange when built, but settling and opening and closing doors and windows creates a lot of gaps over time.

Temperature Delta

This is something you have no control over, but it makes a big difference in the calculation of savings.

If you live in a place like San Francisco, you get average daily high temperatures of about 72 F and average daily low temps of about 46 F.

Cooling in SF is mostly a matter of opening a window at night and staying in the shade in the day time.

Heating is almost as easy. Even on the coldest nights of the coldest times of the year, a warm blanket in a tent is good enough to keep you comfortable. And (most) people in San Francisco have better living situations than that.

In contrast, Northern Minnesota has an average daily high of about 76 F in July and an average daily low of -3 F in January.

Cooling is still not a problem, but there's a huge difference between comfortable temperatures and what it's like outside in Jan.

That temperature delta of about 70 degrees creates much denser air outside and so the pressure for it to get inside is increased. All of the surfaces of the building are also getting a large gradient of heat across their thickness so that the 67 degree air in the house is coming into contact with walls that are something above -3 F on the outside, and something below the 67 F air.

That creates a convection of air against the walls and other surfaces, further increasing the heat transfer just like a breeze makes any air feel colder.

Even in the hottest climates in the US, the average daily high temperatures are only around 100 F. That, while uncomfortable, is only about 30 degrees from a comfortable temperature. So, buildings are not protected much against heat by comparison to how much protection against cold in colder climates.

Solar Gain

The last consideration for putting up plastic window coverings is Solar Gain. Using plastic coverings on windows has almost no impact on how much the sunlight will impact the temperature of a building.

Though this kind of plastic treatment won't make such difference, having sunlight hit the interior of a building can have a huge impact on the temperature.

Buildings can see significant heat gains in the winter by allowing the sunlight in. They should be shielded from sunlight in the summer to avoid the same.

There are plastic films that can be put on windows, (ideally the outermost panes) to reflect much of the energy of the sunlight away. Those can make some difference to reduce summer cooling needs.

Finding Air Leaks

You can use smoke from incense or some other very visible source to track where the air is escaping the building.

Simply wait until after dark, ready a flashlight, light a stick of incense, turn off all the lights, and walk around with it following the smoke as it leaves the building. Those will be your problem areas.

If the temperature difference is low, you can put a fan in a window blowing air into the building to create the pressure needed. But this might cause so much turbulence in the room with the fan that it's hard to see the smoke. In that case, simply hold the smoke source near suspected holes and test them to see if it exits there.

If the temp difference is high, you may be able to just use the natural pressure created by the existing holes. If that's not enough, open a door or window to the outside a little bit. The temporary loss of energy for those few minutes will be more than made up for by the thousands of hours of better sealing later.

Summary

The higher the temperature difference is for your climate, the more helpful it will be to reduce airflow and increase insulation.

Airflow reduction is usually easier, and cheaper, and more effective than adding insulation.

Plastic window coverings do add some insulation against thermal conduction by adding another barrier. But their primary benefit comes from closing air gaps.

How much savings is a factor of how inefficient your building envelope and insulation are and how much difference in temperature there is from outside to inside.

When doing weatherproofing like this, also seal doorways so air infiltration is reduced there.

Keep passages from one floor to the next closed off if possible to reduce the effect of air pressure between floors causing more infiltration.

The plastic should seal off the entire window frame, not just the inside sashes which hold the glass. The air infiltration is mostly from the gaps in the fit between sashes and the frame, and sometimes from the frame itself like in the case of frames that have ropes and pulleys.

Caulking around the frame against the wall can also help.

Keeping window film on all year round can make some difference in the warmer periods, mostly by stopping air exchange. But it's not as significant of an actual energy savings as it can be with larger temperature differences in colder periods.

That said, air cooling is usually powered by electricity at lower efficiencies than air heating which is usually powered by burning fuel at higher efficiencies. Electricity is also usually more expensive per unit of energy. So you may get a higher financial savings ratio while using air conditioning for every bit of energy you can save.

Overall, I'd suggest that if you are in a climate with high fluctuations of temperature, it's worth keeping plastic shrink wrap film up all year long until you find yourself in a building that has more energy efficient construction.

It's hard to give specific numbers on how much you might save without doing physical testing on your specific building. But I hope this information helps in understanding and deciding in your particular situation.

I know this is an old post. But I found it while looking for some specifics, so I'm sure others are ending up here as well. I wanted to clarify and correct some incorrect information.

Answer 15

I use the window film every winter living in Illinois. I also put a low e window film made by Gila on my windows that reflects summer sun's heat back. The big difference was how warm the areas hit by sun beaming through windows inside the house no longer were. I found the film at a large discount chain hardware store where you'll save big money ;) i spent close to $80 to do 14 large windows and a patio door. It paid for itself in lowered summer a/c bills the first year used.

Answer 16

Answer to plastic window film. No not in February. Wait till Fall. Plastic film inside or diy plastic storm exterior is no where near 50 percent! Barely 30 percent efficiency. Old single pane windows are not the problem. Adding storm windows will help; however Problem is around the window, around the door, around the floor. Or any other area TWO materials are connected. Rental properties are not insulated as well due to local min code requirements.