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gbwillson

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Reply with quote  #11 
You could also look at something like these:
https://www.menards.com/main/doors-windows-millwork/weather-stripping/60-vinyl-sheeting-framing-strips/slb60a/p-1492582940920.htm

And this bulk shrink film:
https://www.menards.com/main/doors-windows-millwork/weather-stripping/84-x-25-bulk-insulation-film/v8425m/p-1492582940323-c-3624.htm?tid=-5557863172257976188&ipos=24


I have no experience with the bulk shrink film, only the 3M and Duck brands. I've also seen 10 mil clear plastic in a 4' width that could be snapped or stapled to a frame. Might hold up for several seasons. 

Greg in MN

PS: You could experiment with a window or two to figure out what works best, but the shrink film goes on sale often, especially nearing the end of the winter.

stmbtwle

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Reply with quote  #12 
Might be of interest:
https://www.energyguide.com/info/window1.asp
https://www.energyguide.com/info/window2.asp

"Windows filled with air or argon work best when the space is about 1/2 inch."

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
KevinH

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Reply with quote  #13 
I went back and calculated the savings with window film for my house using the builditsolar calculator.  This calculator only does the savings for heating (not cooling).  I used a MN DNR site to determine the heating degree days for just the part of the year when I have the window film on (about 6500).

https://www.builditsolar.com/References/Calculators/InsulUpgrd/InsulUpgrade.htm
http://www.dnr.state.mn.us/climate/historical/energy.html

Assuming the double pane windows are R2 and 1 layer gives R3 and 2 layers give R4, I got:
1 layer saves 19 cents / square foot / heating season
2 layers saves 28 cents / square foot / heating season

Not a huge savings, but as long as the material costs are kept low (frame and film) and they last for multiple years, it is worth it.

This is for natural gas heating with an efficient furnace.  For electricity, propane, or less efficient furnaces, the savings would be higher.  For example, with propane at $1.76/gallon it went up to 58 cents / sq ft for 1 layer.

There are lots of good articles on ways to insulate windows at builditsolar.com.

Kevin H
MN
gbwillson

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Reply with quote  #14 
Kevin-

So if I have 10 windows, each roughly 9sf, I'll save $19 per heating season for one layer, and $25 if I use two? I hope my math is wrong, as the time and materials would cost far more than that. But it might make sense for a few key windows, it would make you feel warmer, so the thermostat could be set lower.

Greg in MN
KevinH

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Reply with quote  #15 
Greg,
If you have natural gas heating and double pane windows, your savings would come out about the same (slight difference depending on furnace efficiency).  Yes, 90 sq ft would be approx $17 / $25 per heating season.  It's more practical with electric and propane heating or for old single pane windows.  For electric heat at 12 cents/KWH I got $0.91 and $1.37/sq ft.

The materials cost (and time) is why I didn't do more of my windows.  The frame would need be a good quality wood so it stays straight and fits well.  Once they are built, the time to install them is minimal, but then you need a place to store them.

I have 2 windows that I don't use so I just leave the film on all year.  For 4 other windows that I don't open in the summer, I put the film on the screen frame and just pop that in during the winter (screen is inside).  No cost beyond the film.  For a sliding glass door in the basement I put some 1/2 inch Styrofoam (leftover packing material) along the bottom half.

Kevin H
MN
Gordy

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Reply with quote  #16 
Thanks Willie,

If I were to redo them it would be interesting to try a smaller gap, but they are working as is. Although my windows are fairly new, the way I did these inserts shows how good/bad the seals on the windows are. At night with a good wind blowing the interior lights reflecting off of the film can move all over the place as the wind pushes past the seals and bows out the film. So the benefit isn't just insulation but infiltration as well.

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Gordy,
Minnesota
SteveGerber

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Reply with quote  #17 
I wonder if it would be at all feasible to make your own deep-vacuum windows like these:

https://www.buildinggreen.com/blog/vacuum-insulated-windows

Make silicone dots on a sheet of tempered glass, seal the edge with silicone and embed a one-way valve in the silicone. Pull a vacuum after silicone is dry using a commercial HVAC vacuum pump. Perhaps you could check the vacuum level periodically at the valve using the pump gauge and vacuum it some more if air is slowly seeping in.
Bert

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Reply with quote  #18 
I just recently made some panels for some of my windows. I made them from 1/2" polisio. Taped the edges and made them tight enough to fit good. I take most of them out during the day, especially the south side and close them up at night.
On the north side there's an unused room, except for the cat, that we just keep them in.

Just had them in a few days but it seems to help.


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Bert K.
Michigan

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SteveGerber

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Reply with quote  #19 
Hey Bert, do you have problems with ice/condensation on the cold glass behind the polyiso? I have some problems with that depending on how much humidity a room has in it.
Bert

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Reply with quote  #20 
Not so far but it's only been a few days. Will keep an eye on that.
We have pretty dry winters though. It has been well below 0 F for a while.

...I just checked my northern window and there is a bit of ice on it.  Maybe I have it too tight?

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Bert K.
Michigan

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